HK1023518B - Pharmaceutical preparations comprised of salts of hyaluronic acid with local anaesthetics - Google Patents

Description

Field of the invention

The present invention relates to a medicament for topical administration comprising a stoichiometrcally neutral salt of hyaluronic acid with benzydamine or bupivacaine, in which 10 - 90% of the carboxy groups of the hyaluronic acid are salified with the benzydamine or bupivacaine and the remaining carboxy groups are salified with an alkaline or alkaline earth metal, wherein the hyaluronic acid has a molecular weight in the range of 50-350 kDa or 500-730 kDa or 750-1,200 kDa.

Field of the invention

European patent No 0197718 B1 granted on December 15, 1993 describes the advantageous use of hyaluronic acid and molecular fractions thereof as vehicles for medicinal substances for 15 topical use and demonstrates that associations of hyaluronic acid with known drugs in various fields of medicine give better effects than the same drugs administered on their own. That patent emphasises above all a greater degree of bioavailability than that obtained with the pharmaceutical formulations used in the past, and this advantage is illustrated especially in the ophthalmic field, where marked compatibility with the corneal epithelium was observed, with subsequent excellent 20 tolerability with no sensitization effects, with the formation of homogeneous and stable films which are perfectly transparent, have excellent adhesive properties and guarantee prolonged bioavailability of the drug.

The above patent discusses the importance of said perfected bioavailability in the veterinary field with regard to the administration of chemotherapeutics. The patent also lists miotic, anti-25 inflammatory, wound healing and antimicrobial effects for ophthalmic use in the fields of boh veterinary and human medicine.

Although EP-A-197 718 discloses stoichiometrically neutral HA salts with pharmacologically active compounds, including, among a long list, local anaesthetics such as dibucaine, benzocaine and lidocaine, and provides molecular weight fractions of HA falling within the intervals in claim 1, it does not disclose or suggest the specific features of the present invention.

Doherty, M.M. et al., Anaesth. Analg., 80, 740 (1995) discloses equimolar quantitites of HA and lidocaine, (page 741, right column, lines 31-35), wherein the HA has a molecular weight of 165 kD (page 741, right column, line 17). One therefore concludes that the percentage of salification is 100%. This document therefore only refers to a very specific composition comprising 100% salification and one particular molecular weight fraction of HA. Further, the HA-lidocaine preparation is not for topical use.

Hassan, H.G. et al., Acta Anaesthesiol. Scand. 29, 384 (1985) discloses solutions with a large excess of base over HA carboxylate groups, and therefore the HA is 100% salified by the base. Further, the molecular weight of HA is an order of magnitude larger than the ranges of the present application, and HA with molecular weight in this range have a much higher intrinsic viscosity than HA with the molecular weight in the range cited in the present application (discussed in D2, page 741, lines 8-25). Thus, the resulting HA solutions have a very different chemical property than the solutions of the present invention.

Detailed description of the invention

It has now been discovered that the use of local anaesthetics, and more precisely basic organic anaesthetics containing amino groups, if used in the form of their stoichiometrically neutral 30 salts with hyaluronic acid, or stoichiometrically neutral salts of hyaluronic acid with such anaesthetics, resulting from partial salification of the hyaluronic acid with said aminic substances and from the salification of the remaining carboxy groups of the acid with inorganic bases deriving from alkaline or alkaline earth metals, not only offers the advantages of enhanced bioavailability and excellent tolerability, but also induce an exceptional increase in the anaesthetic effect. This result is of great importance in the ophthalinological field but can be used in other fields as well. It constitutes a specific technical effect over and above the benefits reported in the aforesaid previous patent.

In the context of the present invention, the term "hyaluronic acid" indicates a purified hyaluronic acid such as those already on the market or described in the literature or in patents such as those obtained by extraction from animal or fermentation sources, or of biotechnological origin, or molecular fractions of hyaluronic acids, likewise purified, such as those described in European patent No. 0138572 (describing commercial products known as Hyalastine and Hyalectin) or hyaluronic acids with higher molecular weights such as the fraction known as Hyaloftil, described in EP 0535200 A1, or other products available on the market Besides the hyaluronic acid described above, its partial esters obtained according to the procedure described in EP 0216453 B1 can-also be used.

The local anaesthetics for use in the preparation of salts with hyaluronic acid according to the present invention are essentially those reported in the literature and/or found on the market or used for clinical purposes, and which contain aliphatic and/or aromatic amino groups (with between 12 and 30 carbon atoms) which can be salified with an acid. While the salts of hyaluronic acid with lidocaine, dibucaine and benzocaine are known, as they are described in the aforesaid European patent No. 0197718 B1, the salts of hyaluronic acid with the following aminic-type local anaesthetics to be used according to the invention are new and constitute a particular object of the invention: tetracaine, amylocaine, bucricaine, bupivacaine, butacaine sulfate, butanilicaine, butoxycaine, carticaine, chloroprocaine, clibucaine, chlormecaine, cyclomethycaine, dimethisoquin hydrochloride, diperodon, diclocaine, ethyl p-piperidine acetylamine benzoate, ethidocaine, hexylcaine, phenacaine, fomocaine, hydroxyprocaine, hydroxytetracaine, ketocaine, oxethazaine, oxybuprocaine, paretoxycaine, piperocaine, piridocaine, pyrrocaine, pramoxine, prilocaine, procaine, propanocaine, propipocaine, propoxycaine, proxymetacaine, ropivacaine, tolycaine, trimecaine, vadocaine and, especially, benzydamine, a drug characterized by anti-inflammatory and local anaesthetic properties.

The salts of hyaluronic acid with a strong anaesthetic effect according to the present invention are above all stoichiometrically neutral salts with the abovesaid aminic bases, that is, the total salts of the polysaccharide with aminic bases. In the partial salts of the polysaccharide with said aminic bases, the degree of salification may vary within an ample range, for example between 10% and 90%, preferably between 20% and 80%, and especially between 50% and 75%, with the remaining carboxy groups of the polysaccharide are salified with one of the abovesaid ions of an alkaline or alkaline earth metal.

A preferred object of the invention is represented by the total and partial salts, as described above, of benzydamine with a hyaluronic acid. It has been observed that salts of this kind not only present a far more pronounced and longer-lasting anaesthetic effect than benzydamine or the hydrochloride thereof but also enhance the anti-inflammatory effect and, surprisingly reduce the irritating action, thus widening the gap between active and irritant concentrations or doses. Indeed, it is known that, as an anaesthetic or anti-inflammatory agent, benzydamine presents some disadvantages, such as the brevity of its topical action, as the drug quickly passes from the application site into the system, and the onset of an irritant action, which occurs at doses not far removed from those required for the desired effects.

It has further been found according to the invention that the activity of the hyaluronic acid salts with anaesthetics can vary depending upon the molecular weight of the hyaluronic acid. For one of the preferred anaesthetics, benzydamine, it was found that the product has the most improved characteristics when salified with a low molecular weight fraction of hyaluronic acid. For another preferred anaesthetic, bupivacaine, it was found that the product has the most improved characteristics when salified with a high molecular weight fraction of hyaluronic acid. It has also been found that of the alkaline and alkaline earth metals, sodium salts are the preferred monovalent salts, and calcium salts are the preferred bivalent salts.

It follows that the new benzydamine salts of the present invention, besides their advantageous application in ophthalmology, like the other anaesthetic bases mentioned previously, have proved to be new drugs with a very wide field of application, for example in inflammatory processes in the mouth or airways such as stomatitis of various origin, tonsillitis or tracheitis, in mucositis caused by radio- or chemotherapy, by surgical or diagnostic intubation, such as bronchoscopy, in dental and gingival disorders in general, including teething trouble in babies, in rhinitis, in inflammatory processes affecting the auditory canal, in conjunctivitis of various origin, in proctological conditions, in traumatic and degenerative-inflammatory processes in the joints, in vulvovaginitis and urethritis of various kinds. including those caused by radio- and chemotherapy, surgical operations, diagnostic manoeuvres, childbirth and, in general, any inflammatory disorder of any kind.

The technical effect of the new hyaluronic acid salts according to the present invention can be demonstrated by the following experimental results relating to its greater anaesthetic action compared to that of the anaesthetic component used on its own (Tables 1-6), in dry inflammation of the eye in rabbit. Benzydamine salts too show a reduction in the substance's irritant action (Tab 7).

BIOLOGICAL TESTS A. ASSESSMENT OF THE ANAESTHETIC EFFECT ON RABBIT CORNEA OF HYALURONIC ACID SALTS WITH LOCAL ANAESTHETICS METHODS Corneal Anaesthesia

Corneal anaesthesia was assessed by the method of Camougis and Tankman (Camougis et al. (1971), "Methods in Pharmacology", Vol. 1, A Schwartz Ed., Appleton-Century-Crofts, New York, p. 1) by measuring the blinking reflex in rabbit. Fifty ml of solution was instilled in the conjunctival sac. The blinking reflex, tested with a bristle, was measured before instillation and then every 5-10 minutes until one hour after treatment. At each test time the degree of anaesthesia was expressed by means of a score of up to 10 given by the number of stimulations before the eye-blink reflex was obtained. The overall anaesthetic effect for each compound was then quantified by the area under curve (AUC) of the degree of anaesthesia over time.

RESULTS

As indicated by the results in Table 1, the hyaluronate salts of lidocaine, bupivacaine and benzydamine present greater local activity than their respective hydrochloride salts. As can be observed the effect of increasing the action of the anaesthetics varies according to the alkaline or alkaline/earth ion; the presence of calcium, unlike sodium, selectively favours lidocaine rather than bupivacaine or benzydamine. Table 1:

Anaesthetic effect in rabbit eye by hyaluronate of lidocaine, bupivacaine, benzydamine (FID 60.20XX) and their respective hydrochloride salts.
Compound*	Dose§ (concentration)	Anaesthesia (AUC)$
Lidocaine HCl	1%	100
FID 60.2070 (100% lidocaine)	1%	167
FID 60.2071 (50% lidocaine - 50% Na)	1%	244
FID 60.2072 (50% lidocaine - 60% Ca)	1%	222
FID 60.2088 (50% lidocaine - 50%K)	1%	200
Bupivacaine HCl	0.125%	100
FID 60.2082 (100% bupivacaine)	0.125%	166
FID 60.2083 (50% bupivacaine - 50% Na)	0.125%	205
FID 60.2084 (50% bupivacaine - 50% Ca)	0.125%	112
Benzydamine Hcl	0.125%	100
FID 60.2096 (50% benzydamine - 50% Na)	0.125%	153
FID 60.2097 (50% benzydamine - 50% Ca)	0.125%	110

Table 1:

* For the hyaluronate salts, the % of active principle and that of alkaline or alkaline earth ion are shown;

§ the doses refer in all cases to the active principle as a hydrochloride salt;

$ AUC measurements of the anaesthetic effect are calculated by taking the reference active principle value as 100.

This ion selectivity has proved to also depend upon the molecular weight of the hyaluronic acid used. As can be seen from Table 2, the ion selectivity only exists in law-molecular-weight hyaluronic acid, specifically molecular weight range of 50-350 kDa (derivatives FID 6020XX), and not in high-molecular-weight hyaluronic acid, molecular weight range of 500-730 Kda and 750-1200 (derivatives FID 61.20XX and FID 62.20XX, respectively). Table 2:

Anaesthetic effect in rabbit eye by hyaluronate salts of bupivacaine, according to the molecular weight of the hyaluronic acid of the alkaline or alkaline earth counterion.
Compound*	Dose $	Anaesthesia (AUC)$
FID 60.2082 (100% bupivacaine)	0.125%	100
FID 60.2083 (50% bupivacaine - 50% Na)	0.125%	123
FID 60.2084 (50% bupivacaine - 50% Ca)	0.125%	84
FID 61.2082 (100% bupivacaine)	0.125%	100
FID 61.2083 (50% bupivacaine - 50% Na)	0.125%	96
FID 61.2084 (50% bupivacaine - 50% Ca)	0.125%	104
FID 62.2082 (100% bupivacaine)	0.125%	100
FID 62.2083 (50% bupivacaine - 50% Na)	0.125%	116
FID 62.2084 (50% bupivacaine - 50% Ca)	0.125%	110

Table 2:

* For the hyaluronate salts, the % of active principle and that of alkaline or alkaline earth ion are shown;

§ the doses refer in all cases to the active principle as a hydrochloride salt;

$ AUC measurements of the anaesthetic effect are calculated by taking the reference product value as 100.

Moreover, as can be seen from Table 3, the degree of activity depends on the molecular weight of the hyaluronic acid used. Table 3:

Anaesthetic effect on rabbit eye by hyaluronate salts of bupivacaine according to the molecular weight of the hyaluronic acid.
Compound*	Dose §	Anaesthesia (AUC)$
Bupivacaine Hcl	0.125%	100
FID 60.2083 (50% bupivacaine - 50% Ca)	0.125%	123
FID 61.2083 (50% bupivacaine - 50% Na)	0.125%	169
FID 62.2083 (50% bupivacaine - 50% Na)	0.125%	168
Bupivacaine Hcl	0.125%	100
FID 60.2084 (50% bupivacaine - 50% Ca)	0.125%	102
FID 61.2084 (50% bupivacaine - 50% Ca)	0.125%	180
FID 62.2084 (50% bupivacaine - 50% Ca)	0.125%	205

Table 3:

* For the hyaluronate salts, the % of active principle and that of alkaline or alkaline earth ion are shown;

§ the doses refer in all cases to the active principle as a hydrochloride salt;

$ AUC measurements of the anaesthetic effect are calculated by taking the reference product value as 100.

Among monovalent alkaline salts, the most active derivatives are obtained by salification with sodium, as can be seen in Table 4, where derivatives of lidocaine with hyaluronic acid having a molecular weight range between 50 and 350 Kda are reported. Table 4:

Anaesthetic effect on rabbit eye by hyaluronate salts of lidocaine and its alkaline salts.
Compound*	Dose §	Anaesthesia (AUC)$
Lidocaine Hcl	0.125%	100
FID 60.2087 (50% lidocaine - 50% Li)	0.125%	197
FID 61.2083 (50% lidocaine - 50% Na)	0.125%	244
FID 62.2083 (50% lidocaine - 50% K)	0.125%	173

Table 4:

§ the doses refer in all cases to the active principle as a hydrochloride salt;

$ AUC measurements of the anaesthetic effect are calculated by taking the reference product value as 100.

The degree of salification influences the biological activity of the derivatives, as can be seen in Table 5, where partial salts with bupivacaine and sodium of hyaluronic acid having a molecular weight range between 500 and 730 Kda are reported in comparison to the hydrochloride and the total salt; and in Table 6, where partial salts with benzydamine and sodium of hyaluronic acid having a molecular weight range between 50 and 350 Kda are reported in comparison to the hydrochloride. Table 5:

Anaesthetic effect on rabbit eye by hyaluronate salts of bupivacaine according to the degree of salification.
Compound*	Dose §	Anaesthesia (AUC)$
Bupivacaine HCl	0.125%	100
FID 61.2110 (50% bupivacaine - 74% Na)	0.125%	171
FID 61.2083 (50% bupivacaine - 50% Na)	0.125%	169
FID 61.2109 (75% bupivacaine - 25% Na)	0.125%	221
FID 61.2082 (100% bupivacaine)	0.125%	314

Table 5:

* For the hyaluronate salts, the % of active principle and that of alkaline ion are shown;

§ the doses refer in all cases to the active principle as a hydrochloride salt;

$ AUC measurements of the anaesthetic effect are calculated by taking the reference product value as 100.

Table 6:

Anaesthetic effect on rabbit eye by hyaluronate salts of benzydamine according to the degree of salification.
Compound*	Dose §	Anaesthesia (AUC)$
Benzydamine HCI	0.125%	100
FID 60.2102 (10% benzydamine - 90% Na)	0.125%	143
FID 60.2101 (25% benzydamine - 75% Na)	0.125%	148
FID 60.2096 (50% benzydamine - 50% Na)	0.125%	153
FID 60.2108 (75% benzydamine - 25% Na)	0.125%	197
FID 60.2107 (90% benzydamine - 10% Na)	0.125%	181

Table 6:

* For the hyaluronate salts, the % of active principle and that of alkaline ion are shown;

$ the doses refer in all cases to the active principle as a hydrochloride salt;

$ AUC measurements of the anaesthetic effect are calculated by taking the reference product value as 100.

B. ASSESSMENT OF THE REDUCTION OF THE IRRITANT EFFECT OF BENZYDAMINE SALTS IN RAT PAW METHODS Irritation

0.1 ml of each of the test solutions (1%, w/v, in hydrochloride salt) was injection into the hind paw of rat. The paw volume was measured with a plethismometer before injection and then 30-60-120-240-480 minutes after. The oedema and consequent irritant effect were measured on the basis of the increase in the volume of the paw. The irritant effect is expressed by the sum of the increase in volume at the various measuring times.

RESULTS

The hyaluronate salt proved to be less irritating than the hydrochloride salt, as indicated by its lesser oedema-forming effect (Table 7). Table 7:

Irritant effect of benzydamine Hcl and FID 60.2108 in rat paw.
Compound	No.	Oedema mean cumulative volume (ml)
Benzydamine Hcl mg	20	529
FID 60.2108 1 mg (75% benzydamine 25% Na)	20	389

In the case of FXD 60.2108, the % of active principle and that of Na ion are indicated.

All doses refer to the active principle as a hydrochloride salt.

METHODS OF PREPARATION

The types of hyaluronic acid and basic anaesthetics to be used as starting products are already known and can be prepared by the known processes, as described hereafter. The invention can be illustrated by the following Examples:

Example 1

The hyaluronic acid sodium salt (molecular weight 50 - 350 Kda) is solubilized in water to a concentration of 16 mg/ml. A column is filled with acid resin Bio-Rad AG50W-X8, pretreated with Hcl 1N, using a glass column fitted with a jacket inside which there is a flow of fluid at 4°C; 5 ml of resin in acid form are loaded in the column and washed with water to a neutral Ph. At this point the solution of hyaluronic acid sodium salt is passed through the resin, and the resulting solution is collected in a container with a thermostat set at 4°C.

The flow in the column is regulated by a peristaltic pump fitted to the outlet of the column. Once all the solution has passed through the column, the resin is washed with water to minimize any loss of product, and the products of these washes are added to the hyaluronic acid solution, thus obtaining a final solution with a concentration of 11.8 mg/ml, expressed as hyaluronic acid.

Example 2

The hyaluronic acid sodium salt (molecular weight 500 - 730 Kda) is solubilized in water to a concentration of 5.0 mg/ml. A column is filled with acid resin Bio-Rad AG50W-X8, pretreated with HCI 1N, using a glass column fitted with a jacket, inside which fluid flows at a temperature of 4°C; 5 ml of resin in acid form are loaded in the column and washed with water until a neutral pH is reached. At this point the hyaluronic acid sodium salt solution is passed through the resin, collecting the resulting solution in a container set at temperature of 4°C.

The fluid in the column is regulated by a peristaltic pump fitted onto the outlet of the column. Once the solution has passed through the column, the resin is washed with water to minimize any loss of product, and the product of these washes is added to the hyaluronic acid solution, thus obtaining a final solution with a concentration of 3.78 mg/ml, expressed as hyaluronic acid.

Example 3

Hyaluronic acid sodium salt (molecular weight 750 - 1200 kDa) is solubilized in water to a concentration of 3.0 mg/ml. A column is filled with acid resin. Bio-Rad AG50W-X8 pretreated with HCI 1N, using a glass column fitted with a jacket through which fluid flows at a temperature of 4°C; 5 ml of resin in acid form is loaded in the column and washed with water to a neutral pH. At this point, the hyaluronic acid sodium salt is passed through the resin, collecting the resulting solution in a container with a thermostat set at 4°C.

The flow through the column is regulated by a peristaltic pump fitted onto the outlet of the column. Once the solution has passed through the column, the resin is washed with water to minimize any loss of product, then adding the product of the washes to the hyaluronic acid solution, thus obtaining a final solution with a concentration of 2.36 mg/ml, expressed as hyaluronic acid.

Example 4

80 ml of an aqueous solution of hyaluronic acid, prepared as described in Example 1, at a concentration of 11.8 mg/ml, is placed in a 100 ml flask. The solution is shaken in a thermostat bath set at 4°C. 0.77 g of benzydamine base is diluted with 10 ml of tert-butanol and the solution is slowly added drop by drop to the hyaluronic acid solution: a white precipitate is formed which disappears within a few hours. The container used to weigh the benzydamine is washed with two 5 ml aliquots of tert-butanol which are then added to the hyaluronic acid solution. The salification reaction is considered to be complete when there is no more suspended precipitate in the solution.

At this point the solution is filtered on a Gooch 4 filter, subdivided into yellow glass bottles and freeze-dried. The stoichiometrically neutral salt of hyaluronic acid with benzydamine is thus obtained.

The benzydamine to use as starting product can be prepared as of fallows: 3.0 g of benzydamine hydrochloride are solubilized in water at a concentration of 50 mg/ml. An equimolar quantity of NaOH 1N is added, plus 5% excess, so as to give the aqueous solution a pH of between 10 and 11.

In these conditions the benzydamine base is released and separates from the water as an oil. It is partitioned with ethyl ether (two 50 ml partitionings) to extract the base completely. The ether phases are pooled dehydrated with anhydrous sodium sulfate, then evaporated to dryness and the oily residue is vacuum-dried. The product thus obtained is tested for purity on TLC (eluent: ethyl acetate/methanol 70:30; Rf = 0.14).

Example 5

80 ml of an aqueous solution of hyaluronic acid, prepared as in Example 1, at a concentration of 11.8 mg/ml is placed in a 100 ml flask. The solution is shaken in a thermostat bath set at 4°C. 0.58 g of benzydamine base diluted with 10 ml of tert-butanol and the solution is slowly added drop by drop to the hyaluronic acid solution: a white precipitate is formed which disappears within a few hours. The container used to weigh the benzydamine is washed with two 5 ml aliquots of tert-butanol which are then added to the hyaluronic acid solution. A few hours later, when there is no more suspended precipitate in the solution, 0.62 ml of NaOH 1N is added and shaken for another 30 minutes.

At this point the solution is filtered through a Gooch G4 filter, subdivided into yellow glass bottles and freeze-dried. The neutral salt, partially salified (75%) with benzydamine and partially salified (25%) with sodium.

The benzydamine to be used as starting product can be prepared as described in Example 4.

Example 6

80 ml of an aqueous solution of hyaluronic acid, prepared as described in Example 1, at a concentration of 11.8 mg/ml, is placed in a 100 ml flask The solution is shaken in a thermostat bath set at 4°C. 0.39 g of benzydamine base is diluted with 10 ml of tert-butanol and the solution is slowly added drop by drop into the hyaluronic acid solution. A white precipitate is formed which disappears within a few hours. The container used to weigh the benzydamine is washed with two 5 ml aliquots of tert-butanol which are then added to the hyaluronic acid solution. Some hours later, when there is no more suspended precipitate present in the solution, 1.25 ml of NaOH 1N are slowly added and the mixture is shaken for another 30 minutes.

At this point the solution is filtered through a Gooch G4 filter, subdivided into yellow glass bottles and freeze-dried. The neutral salt, partially salified (50%) with benzydamine and partially salified (50%) with sodium is thus obtained.

The benzydamine used as starting product can be prepared as described in Example 4.

Example 7

80 ml of an aqueous solution of hyaluronic acid, prepared as described in Example 1, at a concentration of 11.8 mg/ml, is placed in a 100 ml flask. The solution is shaken in a thermostat bath set at 4°C. 0.39 g of benzydamine base is diluted with 10 ml of tert-butanol and the solution is slowly added drop by drop to the hyaluronic acid solution: a white precipitate is formed which disappears within a few hours. The container used to weigh the benzydamine is washed with two 5 ml aliquots of tert-butanol which are then added to the hyaluronic acid solution. Some hours later, when there is no longer any suspended precipitate in the hyaluronic acid solution, 92.6 mg of Ca(OH)₂ are added and the mixture is shaken for several hours. The salification reaction is considered to be complete when there is no more precipitate in the solution.

At this point the solution is filtered through a Gooch G4 filter, subdivided into yellow glass bottles and freeze-dried. The neutral salt, partially salified (50%) with benzydamine and partially salified (50%) with calcium, is thus obtained.

The benzydamine used as starting product can be prepared as described in Example 4.

Example 8

250 ml of an aqueous solution of hyaluronic acid, prepared as in Example 2, at a concentration of 3.78 mg/ml, is placed in a 500 ml flask The solution is shaken in a thermostat bath set at 4°C. 0.39 g of benzydamine base is diluted with 10 ml of tert-butanol and the solution is slowly added drop by drop to the hyaluronic acid solution. A white precipitate is formed which disappears within a few hours. The container used to weigh the benzydamine is washed with two 10 ml aliquots of tert-butanol which are then added to the hyaluronic acid solution. Some hours later, when there is no longer any suspended precipitate in the hyaluronic acid solution, 1.25 ml of NaOH 1N are added and the mixture is shaken for another 30 minutes.

At this point the solution is filtered through a Gooch G4 filter, subdivided into yellow glass bottles and freeze-dried. The neutral salt, partially salified (50%) with benzydamine and partially salified (50%) with calcium, is thus obtained.

The benzydamine used as starting product can be prepared as described in Example 4.

Example 9

250 ml of an aqueous solution of hyaluronic acid, prepared as in Example 2, at a concentration of 3.78 mg/ml, is placed in a 500 ml flask. The solution is shaken in a thermostat bath set at 4°C. 0.39 g of benzydamine base is diluted with 10 ml of tert-butanol and the solution is slowly added drop by drop to the hyaluronic acid solution: a white precipitate is formed which disappears within a few hours. The container used to weigh the benzydamine is washed with two 5 ml aliquots of tert-butanol which are then added to hyaluronic acid solution. A few hours later, when there is no longer any suspended precipitate in the solution, 92.6 mg of Ca(OH)₂ is added and the mixture is shaken for a few hours. The salification reaction is considered to be complete when there is no more precipitate in the solution.

At this point the solution is filtered through a Gooch G4 filter, subdivided into yellow glass bottles and freeze-dried. The neutral salt, partially salified (50%) with benzydamine and partially salified (50%) with calcium is thus obtained.

The benzydamine used as starting product can be prepared as described in Example 4.

Example 10

400 ml of an aqueous solution of hyaluronic acid, prepared as in Example 3, at a concentration of 2.36 mg/ml, is placed in a 500 ml flask. The solution is shaken in a thermostat bath set at 4°C. 0.39 g of benzydamine base is diluted with 10 ml of tert-butanol and the solution is slowly added drop by drop to the hyaluronic acid solution. A white precipitate is formed which disappears within a few hours. The container used to weigh the benzydamine is washed with two 10 ml aliquots of tert-butanol which are then added to the hyaluronic acid solution. Some hours later, when there is no more suspended precipitate in the solution, 1.25 ml of NaOH is added and the mixture is shaken for another 30 minutes.

At this point the solution is filtered through a Gooch G4 filter, subdivided into yellow glass bottles and freeze-dried. The neutral salt, partially salified (50%) with benzydamine and partially salified (50%) with sodium is thus obtained.

The benzydamine used as starting product can be prepared as described in Example 4.

Example 11

400 ml of an aqueous solution of hyaluronic acid, prepared as in Example 3, at a concentration of 2.36 mg/ml, is placed in a 500 ml flask. The solution is shaken in a thermostat bath set at 4°C. 0.39 g of benzydamine base is diluted with 10 ml of tert-butanol and the solution is slowly added drop by drop to the hyaluronic acid solution. A white precipitate is formed which disappears within a few hours. The container used to weigh the benzydamine is washed with two 5 ml aliquots of tert-butanol which are then added to the hyaluronic acid solution. Some hours later, when there is no more suspended precipitate in the solution, 92.6 mg of Ca(OH)₂ is added and the mixture is shaken for another few hours. The salification reaction is considered to be complete when there is no longer any precipitate in the solution.

At this point the solution is filtered through a Gooch G4 filter, subdivided into yellow glass bottles and freeze-dried. The neutral salt, partially salified (50%) with benzydamine and partially salified (50%) with calcium is thus obtained.

The benzydamine used as starting product can be prepared as described in Example 4.

Example 12

80 ml of an aqueous solution of hyaluronic acid, prepared as in Example 1, at a concentration of 11.8 mg/ml, is placed in a 100 ml flask. The solution is shaken in a thermostat bath set at 4°C. 0.72 g of bupivacaine base is added in solid form to the solution and shaken for several hours. The salification reaction is considered to be complete when there is no longer any suspended precipitate in the solution.

At this point the solution is filtered through a Gooch G4 filter, subdivided into yellow glass bottles and freeze-dried. The stoichiometrically neutral salt of hyaluronic acid with bupivacaine is thus obtained.

The bupivacaine used as starting product can be prepared as follows: 3.0 g of bupivacaine hydrochloride is solubilized in water at a concentration of 25 mg/ml. An equimolar quantity of NaOH 1N is added slowly, plus 5% excess, so as to bring the aqueous solution to a pH of between 10 and 11. In these conditions the bupivacaine base is released and separates from the water as a precipitate. The precipitate is filtered through a Gooch G4 filter, washed several times with water, then vacuum-dried. The product thus obtained is tested for purity by assessing its fusion point (107°-108°) and TLC (eluent:ethyl acetate/methanol 70:30; Rf = 0.79).

Example 13

80 ml of an aqueous solution of hyaluronic acid, prepared as in Example 1, at a concentration of 11.8 mg/ml, is placed in a 100 ml flask The solution is shaken in a thermostat bath set at 4°C.

0.54 g of bupivacaine base is added in solid form to the solution and shaken. Several hours later, when there is no longer any suspended precipitate in the solution, 0.62 ml of NaOH 1N is slowly added and shaken for another 30 minutes. At this point the solution is filtered through a Gooch G4 filter, subdivided into yellow glass bottles and freeze-dried. The neutral salt, partially salified (75%) with bupivacaine and partially salified (25%) with sodium, is thus obtained.

The bupivacaine used as starting product can be prepared as described in Example 12.

Example 14

80 ml of an aqueous solution of hyaluronic acid, prepared as in Example 1, at a concentration of 11.8 mg/ml, is placed in a 100 ml flask. The solution is shaken in a thermostat bath set at 4°C.

0.36 g of bupivacaine base is added in solid form to the solution and shaken. Several hours later, when there is no longer any suspended precipitate in the solution, 1.25 ml of NaOH 1N are slowly added and shaken for another 30 minutes.

At this point the solution is filtered through a Gooch G4 filter, subdivided into yellow glass bottles and freeze-dried. The neutral salt, partially salified (50%) with bupivacaine and partially salified (50%) with sodium, is thus obtained.

The bupivacaine used as starting product can be prepared as described in Example 12.

Example 15

80 ml of an aqueous solution of hyaluronic acid, prepared as in Example 1, at a concentration of 11.8 mg/ml, is placed in a 100 ml flask. The solution is shaken in a thermostat bath set at 4°C. 0.36 q of bupivacaine base is added in solid form to the solution and shaken. Several hours later, when there is no longer any suspended precipitate in the solution, 46.3 mg of Ca(OH)₂ 1N are added and shaken. The salification reaction is considered to be complete when there is no longer any precipitate in the solution.

At this point the solution is filtered through a Gooch G4 filter, subdivided into yellow glass bottles and freeze-dried. The neutral salt, partially salified (50%) with bupivacaine and partially salified (50%) with calcium, is thus obtained.

The bupivacaine used as starting product can be prepared as described in Example 12.

Example 16

250 ml of an aqueous solution of hyaluronic acid, prepared as in Example 2, at a concentration of 3.78 mg/ml is placed in a 500 ml flask. The solution is shaken in a thermostat bath set at 4°C. 0.72 g of bupivacaine base is added in solid form to the solution and shaken for several hours. The salification reaction is considered to be complete when there is no longer any suspended precipitate in the solution.

At this point the solution is filtered through a Gooch G4 filter, subdivided into yellow glass bottles and freeze-dried. The stoichiometrically neutral salt of hyaluronic acid with bupivacaine is thus obtained.

The bupivacaine used as starting product can be prepared as described in Example 12.

Example 17

250 ml of an aqueous solution of hyaluronic acid, prepared as in Example 2, at a concentration of 3.78 mg/ml, is placed in a 500 ml flask. The solution is shaken in a thermostat bath set at 4°C. 0.54 g of bupivacaine base is added in solid form to the solution and shaken. Several hours later, when there is no longer any suspended precipitate in the solution, 0.62 ml of NaOH 1N are slowly added and shaken for another 30 minutes.

At this point the solution is filtered through a Gooch 4 filter, subdivided into yellow glass bottles and freeze-dried. The neutral salt partially salified (75%) with bupivacaine and partially salified (25%) with sodium is thus obtained.

The bupivacaine used as starting product can be prepared as described in Example 12.

Example 18

250 ml of an aqueous solution of hyaluronic acid, prepared as in Example 2, at a concentration of 3.78 mg/ml, is placed in a 500 ml flask. The solution is shaken in a thermostat bath set at 4°C. 0.36 g of bupivacaine base is added in solid form to the solution and shaken. Several hours later, when there is no longer any suspended precipitate in the solution, 1.25 ml of NaOH 1N is slowly added and shaken for another 30 minutes.

At this point the solution is filtered through a Gooch G4 filter, subdivided into yellow glass bottles and freeze-dried. The neutral salt partially salified (50%) with bupivacaine and partially salified (50%) with sodium is thus obtained.

The bupivacaine used as starting product can be prepared as described in Example 12.

Example 19

250 ml of an aqueous solution of hyaluronic acid, prepared as in Example 2, at a concentration of 3.78 mg/ml, is placed in a 600 ml flask. The solution is shaken in a thermostat bath set at 4°C. 0.36 g of bupivacaine base is added in solid form to the solution and shaken. Several hours later, when there is no longer any suspended precipitate in the solution, 46.3 mg of Ca(OH)₂ is added and shaken. The salification reaction is considered to be complete when there is no longer any suspended precipitate in the solution.

At this point the solution is filtered through a Gooch G4 filter, subdivided into yellow glass bottles and freeze-dried. The neutral salt partially salified (50%) with bupivacaine and partially salified (50%) with calcium is thus obtained.

The bupivacaine used as starting product can be prepared as described in Example 12.

Example 20

400 ml of an aqueous solution of hyaluronic acid, prepared as in Example 3, at a concentration of 2.36 mg/ml, is placed in a 500 ml flask. The solution is shaken in a thermostat bath set at 4°C. 0.72 g of bupivacaine base is added in solid form to the solution and shaken for several hours. The salification reaction is considered to be complete when there is no longer any suspended precipitate in the solution.

At this point the solution is filtered through a Gooch G4 filter, subdivided into yellow glass bottles and freeze-dried. The stoichiometrically neutral salt of hyaluronic acid with bupivacaine is thus obtained.

The bupivacaine used as starting product can be prepared as described in Example 12.

Example 21

400 ml of an aqueous solution of hyaluronic acid, prepared as in Example 3, at a concentration of 2.36 mg/ml, is placed in a 500 ml flask. The solution is shaken in a thermostat bath set a 4°C. 0.54 g of bupivacaine base is added in solid form to the solution and shaken. Several hours later, when there is no longer any suspended precipitate in the solution, 0.62 ml of NaOH 1N are slowly added and shaken for another 30 minutes.

At this point the solution is filtered through a Gooch G4 filter, subdivided into yellow glass bottles and freeze-dried. The neutral salt partially salified (75%) with bupivacaine and partially salified (25%) with sodium is thus obtained.

The bupivacaine used as starting product can be prepared as described in Example 12.

Example 22

400 ml of an aqueous solution of hyaluronic acid, prepared as in Example 3, at a concentration of 2.36 mg/ml, is placed in a 500 ml flask. The solution is shaken in a thermostat bath set at 4°C. 0.36 g of bupivacaine base is added in solid form to the solution and shaken. Several hours later, when there is no longer any suspended precipitate in the solution, 1.25 ml of NaOH 1N are slowly added and shaken for another 30 minutes.

At this point the solution is filtered through a Gooch G4 filter, subdivided into yellow glass bottles and freeze-dried. The neutral salt partially salified (50%) with bupivacaine and partially salified (50%) with sodium is thus obtained.

The bupivacaine used as starting product can be prepared as described in Example 12.

Example 23

400 ml of an aqueous solution of hyaluronic acid, prepared as in Example 3, at a concentration of 2.36 mg/ml, is placed in a 500 ml flask. The solution is shaken in a thermostat bath set at 4°C. 0.36 g of bupivacaine base is added in solid form to the solution and shaken. Several hours later, when there is no longer any suspended precipitate in the solution, 46.3 mg of Ca(OH)₂ is slowly added and shaken. The salification reaction is considered to be complete when there is no longer any precipitate in the solution.

At this point the solution is filtered through a Gooch G4 filter, subdivided into yellow glass bottles and freeze-dried. The neutral salt partially salified (50%) with bupivacaine and partially salified (50%) with calcium is thus obtained.

The bupivacaine used as starting product can be prepared as described in Example 12

Example 24

80 ml of an aqueous solution of hyaluronic acid, prepared as in Example 1 at a concentration of 11.8 mg/ml, is placed in a 100 ml flask. The solution is shaken in a thermostat bath set at 4°C. 0.59 g of lidocaine base is added in solid form to the solution and shaken for several hours. The salification reaction is considered to be complete when there is no longer any suspended precipitate in the solution.

At this point the solution is filtered through a Gooch G4 filter, subdivided into yellow glass bottles and freeze-dried. The stoichiometrically neutral salt of hyaluronic acid with lidocaine is thus obtained.

The lidocaine used as starting product can be prepared as follows; 3.0 g of lidocaine hydrochloride is solubilized in water to a concentration of 25 mg/ml. An equimolar quantity of NaOH is slowly added, plus an excess of 5%, so as to give the aqueous solution a pH of between 10 and 11. In these conditions, lidocaine base is released and this separates from the water in the form of a precipitate. The precipitate is filtered through a Gooch G4 filter, washed several times with water and then vacuum-dried. The purity of the product thus obtained is tested by means of its fusion point (68°-69°C) and TLC (eluent: ethyl acetate/methanol 70:30;Rf=0.81)

Example 25

80 ml of an aqueous solution of hyaluronic acid, prepared as in Example 1, at a concentration of 11.8 mg/ml, is placed in a 100 ml flask. The solution is shaken in a thermostat bath set at 40°C. 0.44 g of lidocaine base is added in solid form to the solution and shaken. Several hours later, when there is no longer any suspended precipitate in the solution, 0.62 ml of NaOH 1N are slowly added and shaken for another 30 minutes.

At this point the solution is filtered through a Gooch G4 filter, subdivided into yellow glass bottles and freeze-dried. The neutral salt partially salified (75%) with lidocaine and partially salified (50%) with sodium is thus obtained.

The lidocaine used as starting product can be prepared as described in Example 24.

Example 26

80 ml of an aqueous solution of hyaluronic acid, prepared as in Example 3, at a concentration of 11.8 mg/ml, is placed in a 100 ml flask. The solution is shaken in a thermostat bath set at 4°C. 0.29 g of lidocaine base is added in solid form to the solution and shaken. Several hours later, when there is no longer any suspended precipitate in the solution, 1.25 ml of NaOH 1N is slowly added and shaken for another 30 minutes.

At this point the solution is filtered through a Gooch G4 filter, subdivided into yellow glass bottles and freeze-dried. The neutral salt partially salified (50%) with lidocaine and partially salified (50%) with sodium is thus obtained.

The lidocaine used as starting product can be prepared as described in Example 24.

Example 27

80 ml of an aqueous solution of hyaluronic acid, prepared as in Example 1, at a concentration of 11.8 mg/ml, is placed in a 500 ml flask. The solution is shaken in a thermostat bath set at 4°C. 0.44 g of lidocaine base is added in solid form to the solution and shaken. Several hours later, when there is no longer any suspended precipitate in the solution, 23 mg of Ca(OH)₂ is added and shaken. The salification reaction is considered to be complete when there is no longer any precipitate in the solution.

At this point the solution is filtered through a Gooch G4 filter, subdivided into yellow glass bottles and freeze-dried. The neutral salt partially salified (75%) with lidocaine and partially salified (25%) salified with calcium is thus obtained.

The lidocaine used as starting product can be prepared as described in Example 24.

Example 28

80 ml of an aqueous solution of hyaluronic acid, prepared as in Example 1, at a concentration of 11.8 mg/ml, is placed in a 100 ml flask. The solution is shaken in a thermostat bath set at 4°C. 0.29 g of lidocaine base is added in solid form to the solution and shaken. Several hours later, when there is no longer any suspended precipitate in the solution, 46.3 mg of Ca(OH)₂ is slowly added and shaken. The salification reaction is considered to be complete when there is no longer any precipitate in the solution.

At this point the solution is filtered through a Gooch G4 filter, subdivided into yellow glass bottles and freeze-dried. The neutral salt partially salified (50%) with lidocaine and partially salified (50%) with calcium is thus obtained

The lidocaine used as starting product can be prepared as described in Example 24.

Example 29

80 ml of an aqueous solution of hyaluronic acid, prepared as in Example 1, at a concentration of 11.8 mg/ml, is placed in a 100 ml flask. The solution is shaken in a thermostat bath set at 4°C. 0.29 g of lidocaine base is added in solid form to the solution and shaken. Several hours later, when there is no longer any suspended precipitate in the solution, 36.5 mg of Mg(OH)₂ is added and shaken. The salification reaction is considered to be complete when there is no longer any precipitate in the solution.

At this point the solution is filtered through a Gooch G4 filter, subdivided into yellow glass bottles and freeze-dried. The neutral salt partially salified (50%) with lidocaine and partially salified (50%) with magnesium is thus obtained,

The lidocaine used as starting product can be prepared as described in Example 24.

Example 30

80 ml of an aqueous solution of hyaluronic acid, prepared as in Example 1, at a concentration of 11.8 mg/ml, is placed in a 100 ml flask. The solution is shaken in a thermostat bath set at 4°C. 0.29 g of lidocaine base is added in solid form to the solution and shaken. Several hours later, when there is no longer any suspended precipitate in the solution, 1.25 ml of LiOH 1N is slowly added and shaken for another 30 minutes.

At this point the solution is filtered through a Gooch G4 filter, subdivided into yellow glass bottles and freeze-dried. The neutral salt partially salified (50%) with lidocaine and partially salified (50%) with lithium is thus obtained.

The lidocaine used as staring product can be prepared as described in Example 24.

Example 31

80 ml of an aqueous solution of hyaluronic acid, prepared as in Example 1, at a concentration of 11.8 mg/ml, is placed in a 100 ml flask. The solution is shaken in a thermostat bath set at 4°C. 0.29 g of lidocaine base is added in solid form to the solution and shaken. Several hours later, when there is no longer any suspended precipitate in the solution, 1.25 ml of KOH 1N is added and shaken for another 30 minutes.

At this point the solution is filtered through a Gooch G4 filter, subdivided into yellow glass bottles and freeze-dried. The neutral salt partial salified (50%) with lidocaine and partially salified (50%) with potassium is thus obtained.

The lidocaine used as starting product can be prepared as described in Example 24.

Example 32

80 ml of an aqueous solution of hyaluronic acid, prepared as in Example 1, at a concentration of 11.8 mg/ml is placed in a 100 ml flask The solution is shaken in a thermostat bath set at 4°C. 0.69 G of benzydamine base are diluted with 10 ml of tert-butanol and the solution is slowly added drop by drop to the hyaluronic acid solution: a white precipitate is formed which disappears within a few hours. The container used to weigh the benzydamine is washed with two 5 ml aliquots of tert-butanol which are then added to the hyaluronic acid solution. A few hours later, when there is no more suspended precipitate in the solution, 0.25 ml of NaOH 1N is added and shaken for another 30 minutes.

At this point the solution is filtered through a Gooch G4 filter, subdivided into yellow glass bottles and freeze-dried. The neutral salt, partially salified (90%) with benzydamine and partially salified (10%) with sodium is thus obtained.

The benzydamine to be used as starting product can be prepared as described in Example 4.

Example 33

80 ml of an aqueous solution of hyaluronic acid, prepared as in Example 1, at a concentration of 11.8 mg/ml is placed in a 100 ml flask. The solution is shaken in a thermostat bath set at 4°C. 0.19 g of benzydamine base are diluted with 10 ml of tert-butanol and the solution is slowly added drop by drop to the hyaluronic acid solution: a white precipitate is formed which disappears within a few hours. The container used to weigh the benzydamine is washed with two 5 ml aliquots of tert-butanol which are then added to the hyaluronic acid solution. A few hours later, when there is no more suspended precipitate in the solution, 1.87 ml of NaOH 1N is added and shaken for another 30 minutes.

At this point the solution is filtered through a Gooch G4 filter, subdivided into yellow glass bottles and freeze-dried. The neutral salt, partially salified (25%) with benzydamine and partially salified (75%) with sodium is thus obtained.

The benzydamine to be used as starting product can be prepared as described in Example 4.

Example 34

80 ml of an aqueous solution of hyaluronic acid, prepared as in Example 1, at a concentration of 11.8 mg/ml is placed in a 100 ml flask. The solution is shaken in a thermostat bath set at 4°C. 0.08 g of benzydamine base are diluted with 10 ml of tert-butanol and the solution is slowly added drop by drop to the hyaluronic acid solution: a white precipitate is formed which disappears within a few hours. The container used to weigh the benzydamine is washed with two 5 ml aliquots of tert-butanol which are then added to the hyaluronic acid solution. A few hours later, when there is no more suspended precipitate in the solution, 2.24 ml of NaOH 1N is added and shaken for another 30 minutes.

At this point the solution is filtered through a Gooch G4 filter, subdivided into yellow glass bottles and freeze-dried. The neutral salt, partially salified (10%) with benzydamine and partially salified (90%) with sodium is thus obtained.

The benzydamine to be used as starting product can be prepared as described in Example 4.

Example 35

80 ml of an aqueous solution of hyaluronic acid, prepared as in Example 1, at a concentration of 11.8 mg/ml is placed in a 100 ml flask. The solution is shaken in a thermostat bath set at 4°C. 0.18 g of bupivacaine base in solid form is added to the solution and shaken. Several hours later, when there is no longer any suspended precipitate in the solution, 1.87 ml of NaOH 1N is slowly added and shaken for another 30 minutes. At this point the solution is filtered through a Gooch G4 filter, subdivided into yellow glass bottles and freeze-dried. The neutral salt, partially salified (25%) with bupivacaine and partially salified (75%) with sodium, is thus obtained.

The bupivacaine used as starting product can be prepared as described in Example 12.

PHARMACEUTICAL PREPARATIONS Preparation 1:

Preparation of a mouthwash containing Benzydamine hyaluronate (75%) 100 ml of solution contain:

• Benzydamine hyaluronate (equal to 134.4 mg of benzydamine base)   357 mg

Excipients

• Glycerol   5000 mg
• ethyl alcohol 95°   7926 mg
• Saccharine   30 mg
• Methyl p-hydroxybenzoate   180 mg
• Propyl p-hydroxybenzoate   20 mg
• Peppermint flavouring   42.62 mg
• Quinoline yellow colouring (E104)   0.87 mg
• Blue patent V colouring (E131)   0.14 mg
• Purified water q.s. to   100 ml

Preparation 2:

Preparation of a spray containing Benzydamine hyaluronate (75%) 100 ml of solution contain:

• Benzydamine hyaluronate (equal to 134.4 mg of benzydamine base)   =  357 mg

Excipients

• Glycerol   5000 mg
• Ethyl alcohol 95°   7926 mg
• Saccharine   30 mg
• Methyl p-hydroxybenzoate   180 mg
• Propyl p-hydroxybenzoate   20 mg
• Peppermint flavouring   42.62 mg
• Purified water q.s. to   100 ml

Preparation 3:

Preparation of a proctological cream containing Benzydamine hyaluronate (75%) 100 ml of cream contain:

• Benzydamine hyaluronate (equal to 448 mg of benzydamine base)   1190 mg

Excipients

• Vaseline   8000 mg
• Vaseline oil   4000 mg
• Lanolin   12000 mg
• Polysorbate 80   5000 mg
• Propylene glycol   6000 mg
• Methyl p-hydroxybenzoate   93.5 mg
• Propyl p-hydroxybenzoate   34 mg
• Lavender essence   42 mg
• Purified water q.s. to   100 ml

Preparation 4:

Preparation of a gynaecological solution containing Benzydamine hyaluronate (75%) 100 ml of solution contain:

• Benzydamine hyaluronate   238 mg

Excipients:

• Trimethylacetylammonium-p-toluene sulfonate   100 mg
• Red rose scent   0.1 ml
• Purified water q.s. to   100 ml

The invention being thus described, it is clear that these methods can be modified in various ways. Said modifications are not to be considered as divergences from the spirit and purposes of the invention, and any modification which would be apparent to an expert in the field comes within the scope of the following claims.

Claims (10)

1. A medicament for topical administration comprising a stoichiometrically neutral salt of hyaluronic acid with benzydamine or bupivacaine, in which 10 - 90% of the carboxy groups of the hyaluronic acid are salified with the benzydamine or bupivacaine and the remaining carboxy groups are salified with an alkaline or alkaline earth metal, wherein the hyaluronic acid has a molecular weight in the range of 50-350 kDa or 500-730 kDa or 750-1,200 kDa.
2. A medicament for topical administration according to claim 1, wherein the alkaline metal is sodium.
3. A medicament for topical administration according to claim 1, wherein the alkaline earth metal is calcium.
4. A medicament for topical administration according to any one of claims 1-3, wherein the carboxy groups of hyaluronic acid are salified with benzydamine or bupivacaine in the range between 70 and 90%.
5. A medicament for topical administration according to claim 4, wherein the carboxy groups of hyaluronic acid are salified with benzydamine in a percentage of about 75%.
6. A medicament for topical administration according to claim 5, wherein the hyaluronic acid has a molecular weight in the range of 50-350 kDa.
7. A medicament as defined in any of claims 1-6 for use in ophthalmology.
8. A medicament as defined in any of claims 1-6 for use in the treatment of inflammatory processes in the mouth or primary airways, including rhinitis, mucositis caused by radiotherapy or chemotherapy, by intubation during surgery or for diagnostic purposes, in periodontal or gingival conditions, in inflammatory processes in the auditory canal, in conjunctivitis of various origin, in vulvovaginitis, urethritis, or for proctological applications.
9. A medicament as defined in claim 6 for use as an anaesthetic.
10. A medicament according to any of the preceding claims, which is in the form of collirium, mouth wash, spray, cream or vaginal solution.