HK1183261B - Replaceable cap for a dosing device - Google Patents

Description

Replaceable cap for a drug dosing device

Technical Field

The present invention relates to a replaceable cap for a drug delivery device, and more particularly to a replaceable cap for a transdermal liquid drug delivery device (e.g. an insulin pen).

Background

Insulin-dependent diabetics need to adhere to a strictly prescribed course of liquid insulin injections to control their diabetes. One popular means of insulin delivery is through a reusable transdermal liquid-medicating device, commonly referred to as an "insulin pen," which includes a plastic syringe having an insulin reservoir and a cap covering the proximal end of the syringe from which insulin is infused through a hypodermic needle.

It is known from several published studies that because diabetic patients require multiple injections of insulin per day, the injection process quickly becomes so commonplace that individual doses may easily be forgotten. There is usually no simple and reliable way to determine-with the insulin pen as normally specified or by checking the injection area-whether a given dose has been administered. Not reaching an insulin dose for a short period of time or inadvertently ingesting too many doses can result in serious short and long term health risks and complications for diabetics, including hyperglycemia and hypoglycemia.

Several attempts have been made in the past to solve this problem. For example, US-2009/0076458 to Nielsen describes an injection device that is itself capable of emitting a flashing signal indicating the time elapsed since the last injection. The flash lamp is provided on the main body of the device. Although US-2009/0076458 attempts to solve the same problem as the present invention, it has the disadvantage of forcing diabetics to abandon and discard their preferred or prescribed insulin delivery systems in favor of new systems, which can be economically prohibitive for many users. Another disadvantage of the injection device disclosed in US-2009/0076458 is that the user has to know the meaning of a specific flashing sequence for indicating the time since the last injection. This can be a significant obstacle for some diabetics, especially young or old patients.

US-2004/0062148 to Skyggebjerg discloses a timing device comprising two device parts separated from each other and together forming a single portable unit. One device part provides the insulin pen and the two device parts remain together when the pen is not in use. The separation of the device parts causes the control action to be initiated. This solution has the disadvantage that the preferred embodiment is complex and requires measuring the experience and training of the user in using the device, as well as the need to carry a separate dedicated and larger device. In other described embodiments, one device portion is integral with a cap having a distal portion adapted to cover the first device. The disclosure does not describe any practical or cost-effective method of detecting separation of the device portions or ensuring proper mating between the cap and the distal portion of the first device in the described embodiments.

Systems have been proposed in which the drug device is placed in a register with a docking-station (docking-station) that functions as a control and indication device, such as WO-03/063754 and WO-99/43283, the latter disclosing a sleeve-like indication device attachable to the rear end of an injection pen. These devices suffer from the disadvantage that additional pieces of the device must be used in conjunction with the insulin pen and are generally complex and expensive.

US 2002/0096543 discloses a portable control device for monitoring the dosage of insulin administration. In certain disclosed embodiments, the control device is provided as a separate block that can be secured to the cap of a conventional injection pen, and the pen body includes a resonant circuit that enables detection of the removal of the cap. The control device includes a transmitter that communicates with a remote console to remind the patient to take a dose and uses a colored light system to indicate the dose that should be taken. The embodiments disclosed in this application are complex to use and understand, may require the abandonment or modification of existing, preferably prescribed or prescribed insulin delivery systems, and are prohibitively expensive for many users.

The applicant believes that the above disadvantages at least partially account for the fact that most insulin pens in use today are not used in combination with any means that assist the user in determining whether a given dose has been administered.

Disclosure of Invention

Object of the Invention

It is an object of the present invention to provide a replaceable cap for a transdermal liquid dosing device which at least partially alleviates some of the problems described above and which will be relatively cost-effective to manufacture and easy to use.

Disclosure of Invention

According to the present invention, there is provided a replaceable cap for a transcutaneous liquid medicating device, comprising an elongated hollow body having a first open end, which may be arranged on a front portion of the medicating device from which a liquid is administered, and a second closed end, opposite the first open end, the cap being detachably received on the medicating device, wherein the cap body comprises a cavity, which accommodates a timer unit coupled to a switch mechanism, which displays the time counted by the timer unit on an outer surface of the cap body, and a timer display unit, wherein when the cap is placed on the medicating device, the switch mechanism is engaged by an engagement portion of a surface of the front portion of the medicating device, and when the cap is removed from the medicating device, the switch mechanism is released, operation of the switch causes the timer unit to reset immediately or after a predetermined period of time, whereby the time since the last reset of the timer unit indicates the time elapsed since the last use of the dosing device, and wherein the elongated hollow body of the cap comprises two main parts, which are injection moulded plastic articles and which are connected to each other to form the cap having the cavity at least partially defined between the two main parts, wherein the two main parts clamp the timer unit and the switch between the two main parts.

Additional features of the present invention provide for a switch in the form of an electromechanical switch that protrudes into an interior of the cap so as to engage an outer surface of the liquid-dosing device; the two main parts are a cap top part and a cap bottom part which are made of injection molding materials; the cap top has a window through which the timer display unit is visible; and the cap bottom comprises a majority of the length of the elongated hollow body.

An additional feature of the present invention provides for the cap top to include a flange having a free end extending toward the first open end and forming a pocket clip.

Additional features of the invention provide a second closed end of the cap having a battery compartment disposed therein; the battery compartment is formed at the top of the cap; and the battery compartment has a cover that fits into place to securely hold the batteries in the battery compartment. The cap may be color-coded to enable a user to match the cap with a particular applicator to distinguish between different applicators.

A further feature of the invention provides a replaceable cap that includes a removable non-conductive membrane initially disposed between the battery and associated battery contacts, the membrane extending through a slit in the top of the cap to form a protruding tongue, the tongue being grippable by a user to pull the membrane out of the battery compartment prior to use of the cap to enable the battery to engage the contacts, the membrane thus preventing the battery from being consumed prior to use of the cap. The slit may be disposed in the cap top adjacent the window and the film is initially disposed to extend across the timepiece display unit such that the film also acts as a protective layer for the timepiece display unit. The portion of the film covering the timer display unit also has numbers printed thereon to mimic the display of the LCD so that the user has an indication of what is displayed after the battery has powered the LCD.

Further features of the invention provide a timer unit comprising electronic circuitry on a Printed Circuit Board (PCB); and the timer unit, the timer display unit and the switch mechanism are assembled together as a single control unit mounted in the chamber.

Additional features of the invention provide a timer display unit that is a low cost four digit digital Liquid Crystal Display (LCD); the timer unit counts from zero; the timer is reset to zero by releasing the switch mechanism, and the timer unit is configured to count minutes using the first two digits and seconds using the last two digits, and then count hours using the first two digits and minutes using the next two digits during the first 59 minutes and 59 seconds elapsed.

An additional feature of the present invention provides a standard sized cavity so that the same control unit can be installed into a number of different caps, where each cap has an adjustable inner surface size to fit a particular type of medicated device, so the control unit can be mass produced for all caps as the economies of scale increase.

Additional features of the invention provide for the switch mechanism to include a spring tab projecting into an interior of the cap body; the spring leaf is oriented such that it has a fixed end closer to the first open end of the cap and a free end closer to the second closed end of the cap, such that the act of inserting the front portion of the medicated device into the cap causes the spring leaf to bend toward the cavity without the free end hooking onto any feature of the front portion of the medicated device; and the spring plate is fitted against the electromechanical switch to activate the switch when the spring plate is bent towards the cavity. The spring leaf may be made of spring steel and sufficiently curved that different shaped fronts of different medicated devices will all engage the spring leaf sufficiently to activate the switch.

Further features of the invention provide for the timer unit to be reset only after a predetermined period of time has elapsed; and the predetermined period of time is between 5 and 12 seconds; thereby preventing the timer unit from being reset in case the user removes the cap only briefly, as it may happen that the user checks the liquid level in the dosing device or that the user removes the cap unintentionally for a short period of time.

An additional feature of the present invention provides the inner dimensions of the replaceable cap body, which can be selected to match the inner dimensions of the existing cap that was originally provided with the drug-delivery device, so that the replaceable cap provides the same or very similar push-in or snap-fit on the drug-delivery device as the existing cap.

Further features of the present invention provide for a disposable medicated device and a replaceable cap that is also disposable but capable of being used in series with respect to at least several disposable medicated devices.

A further feature of the present invention provides for the timer display unit to include a battery level indicator or alarm that provides an indication when the battery is low. The cap may be disposable after the battery is depleted, or the lid of the battery compartment may be removable to allow the user to replace the battery.

An additional feature of the present invention provides for the drug-dosing device to be an insulin pen comprising a reservoir and a hypodermic needle disposed at the front of the drug-dosing device.

The present invention extends to a replaceable cap for a transcutaneous liquid medicating device, comprising an elongated hollow body having a first open end disposable on a front portion of the medicating device from which a liquid is administered and a second closed end opposite the first end, characterized in that the cap has two main injection molded plastic parts connected together to form a cap body, the two parts sandwiching a control unit in a cavity defined therebetween, wherein the control unit comprises a timer unit, a timer display unit on an outer surface of the cap body displaying the time counted by the timer, and a switch mechanism configured to be activated when the cap is placed on the medicating device and/or when the cap is removed from the medicating device, activation of the switch mechanism causing the timer unit to reset immediately or after a predetermined period of time, such that the time since the last reset of the timer unit indicates the last time since the medicating device The time elapsed after use.

Drawings

The invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

FIG. 1A is a perspective view of an alternative cap and medicated device according to the present invention, with the cap separated from the medicated device;

FIG. 1B is similar to FIG. 1A, but shows an alternative cap on the medicated device;

FIG. 2 is an exploded view of components of the alternative cap of FIG. 1;

FIG. 3 is a top view of an alternative cap on the medicated device;

FIG. 4 is a cross-sectional view taken along line A-A of FIG. 3; and

fig. 5 is a state diagram showing a plurality of states that the control unit of the cap can assume.

Detailed Description

Fig. 1A shows a perspective view of an alternative cap (10) and associated medicated device (12) according to the present invention. The cap includes an elongated hollow body (14), the elongated hollow body (14) having a first open end (16) and a second closed end (18) opposite the first open end. In this embodiment, the dosing device is a disposable insulin pen comprising a reservoir (20) in which the liquid insulin is stored, a piston (22) at the rear end (24) of the insulin pen, and a hypodermic needle (not shown) at the tip of the front part (26) of the insulin pen, from which the insulin is administered. The hypodermic needle has a removable sheath (28) for covering the needle. Along the insulin pen body and near the front, there is provided a transparent portion or portions (30) through which the level of liquid insulin can be visually checked. The insulin pen may be an existing disposable insulin pen as commonly available on the market, provided with an existing cap that can be simply discarded and replaced by the replaceable cap of the present invention.

The first open end (16) of the cap may be placed over the front portion (26) of the drug delivery device such that the cap fits over and covers the drug delivery device, as shown in fig. 1B, which is shown on the drug delivery device in fig. 1B. The cap is removably secured to the dosing device and has adjustable internal dimensions (not shown) to suit a particular type of applicator device, the internal dimensions being selected to match an existing cap originally provided on the applicator device, such that the cap of the present invention provides the same or very similar push-in or snap-fit on the applicator device as existing caps.

Fig. 2 shows an exploded view of the components of the alternative cap (10). The replaceable cap comprises two main parts: a cap top (40) and a cap bottom (42) joined with the cap top (40) to form a cap. The cap top and the cap bottom are injection molded parts and may be joined together by clamps, ultrasonic welding, glue, or any other suitable means. The cap bottom forms a majority of the length of the elongated cap body, and the cap top has a rectangular window (44) disposed therein. A flange (46) extends along the upper side of the cap top (40) towards the first open end (16) to form a pocket clip.

When assembled, a cavity (48) is formed between the cap top and the cap bottom. The cavity opens into an interior (50) of the cap and is aligned with the window (44). The cavity houses a control unit (52), the control unit (52) is snugly fitted into the cavity and sandwiched by the cap top and the cap bottom, and the control unit (52) includes a Printed Circuit Board (PCB) (51) on which a timer unit (54), a switch mechanism (56), and a timer display unit (58) are mounted. In some embodiments, the PCB may be a single layer PCB and be 0.5mm thin. In this embodiment, the timer display unit (58) is a low cost four digit digital Liquid Crystal Display (LCD) that displays the time counted by the timer unit, and is aligned with the window (44) such that the timer display unit is visible on the upper surface of the cap top. The timer display unit may include a low battery alarm indicator and is preferably not backlit to conserve power. The timer unit consists of a microcontroller counter and an oscillation crystal, and is preferably a 4-bit, low voltage (e.g., 0.9-1.7V) mask ROM microcontroller with a built-in LCD driver. Digital watch integrated circuits may also be used for this purpose.

At the second closed end (18) of the cap, a battery compartment (60) is formed at the top of the cap. The battery compartment is provided at the second closed end so as to be as far as possible from the liquid insulin reservoir of the dosing device, and the battery compartment is formed as a separate compartment to minimize the risk that any battery leakage may contaminate the insulin stored in the insulin reservoir of the insulin pen. The battery may be a silver oxide non-rechargeable 1.5V battery with sufficient stored charge to power the control unit for at least several months (e.g., even over 12 months and as long as 36 months), thus the cap can be used continuously with respect to a plurality of disposable insulin pens.

The battery is held in place against a set of electrical contacts (not shown) by a cover (64) that is mounted in place. The cover is preferably color-coded to allow the user to distinguish between multiple insulin pens being used at any given time. In certain embodiments, the cap is disposable and intended to be discarded after the battery is depleted, in which case the lid may be permanently attached in place by adhesive, ultrasonic welding or deformation clamp formation. In other embodiments, the battery may be replaced by prying or unscrewing the cover to open the cover.

Fig. 3 shows a top view of an alternative cap (10) and a medicated device (12) with the cap on the medicated device, and fig. 4 shows a cross-sectional view along line a-a of fig. 3. As shown in fig. 4, the switch mechanism comprises a spring leaf (70), the spring leaf (70) being partly outside the cavity in which the control unit (52) is mounted and protruding into the interior (50) of the cap. The spring leaf is oriented such that it has a fixed end (72) closer to the first open end (16) of the cap and a free end (74) closer to the second closed end (18) of the cap. The spring plate is mounted so as to abut an electromechanical switch (76) on the PCB to activate the switch when the spring plate bends toward the cavity. The act of inserting the front portion (26) of the insulin pen (12) into the open end of the cap causes the surface of the front portion to abut the spring tab and causes the spring tab to flex toward the cavity and depress the switch (76). Because the spring tab is oriented so that its free end is closer to the closed end of the cap, the free end does not hook onto any features that may be present on the front (26) of the medicated device (such as ridges or shoulders), as may occur if the spring tab is oriented in the opposite direction. The spring plate is preferably made of spring steel and has sufficient curvature so that the differently shaped front portions of different insulin pens will all engage the spring plate sufficiently to activate the switch.

Importantly, the cavity (50) in which the control unit (52) is mounted is selected to be of a standard size so that the same control unit can be mounted into a variety of different caps according to the present invention, each cap having an adjustable inner surface size to fit a particular type of applicator. Preferably, the inner surface dimensions of each type of cap may be selected to match the inner surface dimensions of the existing cap initially provided with the type of insulin pen, so that the replaceable cap of the present invention is provided with a snap fit that is the same as or very similar to the existing cap provided with the pen. A cavity with standard dimensions enables the same control unit to be fitted into each different type of cap, so that the control unit can be mass-produced with increasing economies of scale. It is also important in this respect that the spring plate has sufficient curvature so that the differently shaped front portions of different insulin pens will all engage the spring plate sufficiently to activate the switch, as described above. Thus, the same switching mechanism can be used on all control units.

As also shown in fig. 4, a removable non-conductive film (78) is disposed between the battery (80) and its associated electrical contacts (not shown). The non-conductive film extends through a slit (84) provided in the cap top adjacent the window and extends across the timepiece display unit (58) and terminates in a projecting tongue (86). The removable non-conductive film will be put in place during the manufacturing process and is intended to remain in place until the cap is actually used by the patient. When the patient is ready to use the cap, the tongue is grasped between the thumb and forefinger and the membrane is then pulled off the timer display unit and away from the battery compartment so that the battery engages the electrical contacts. Thus, the membrane prevents the battery from being consumed prior to use, greatly increasing the shelf life of the replaceable cap of the present invention. The portion of the film covering the timer display unit may also have printed numbers on the film to mimic the display of the LCD so that the user has an indication of what will be displayed after the battery has powered the LCD.

In use, an electromechanical switch (76) is activated when the cap is fully inserted into the insulin pen, and the switch is released when the cap is removed from the insulin pen. The engagement or disengagement of the switch causes the timer unit to reset the timer after a predetermined period of time, preferably between 5 and 12 seconds, most preferably about 8 seconds, has elapsed. Based on resetting the timer, the timer display unit resets the LCD to zero, after which the timer unit begins to display the elapsed time since the timer was last reset. In this way, the replaceable cap of the present invention indicates to the patient the time elapsed since the last use of the insulin pen.

The reason why the timer is preferably not reset immediately upon engagement or release of the switch is that the user of the insulin pen sometimes removes the insulin pen cap briefly to check the level of liquid insulin only through the transparent segment (30) without performing an insulin injection. This action usually takes only 2 or 3 seconds, whereas the action of injecting insulin usually takes at least 12 seconds. Also, it may happen that the user unintentionally removes or partially removes the cap for a short period of time, for example when swinging a pen or other device. An assumption is therefore made that if the cap is left for longer than a predetermined time, the user has ingested a prescribed dose of insulin and resets the timer. In this way, by simply looking at the digital timer display unit, the patient can confirm the time that has elapsed since the last dose occurred, thus avoiding the anxiety of knowing whether a previous dose has been forgotten or has just been taken, and reducing the risk of accidental overdosing or underdosing occurring.

In a preferred embodiment, a four digit LCD counts up from zero and counts minutes using the first two digits and seconds using the last two digits within the first 59 minutes and 59 seconds after the timer was last reset. When the timer reaches 60 minutes, then the first two digits are used to count hours and the second two digits are used to count minutes. In this way, only a four digit LCD may be used instead of the more expensive six digit LCD, while still being able to indicate seconds to the user within the first hour after the last insulin dose.

Fig. 5 is a state diagram showing states that the control unit can take. When packaged, the control unit is in a packaged state (100) during which no display is shown on the LCD because the battery is off. Once the film is removed, the control unit enters a reset state (102) during which the timer is reset and held at zero and all segments of the LCD blink. If it happens that the cap is first placed on the insulin pen, pressing the switch causes the control unit to enter a "cap on" state (104), during which the timer runs and the run time is displayed on the LCD. During the "cap on" state, the four digit timer uses the first two digits for minutes and the last two digits for seconds for the first 59 minutes and 59 seconds elapsed, followed by the first two digits for hours and the last two digits for minutes as described above. The timer may be configured to count up to 99 hours 59 minutes. If the switch is released after the "cap on" state, as when the cap is removed, the control unit enters an intermediate state (106). During the intermediate state, the timer continues to run for a predetermined time (e.g., 8 seconds). If the switch is pressed again before the predetermined time has elapsed (e.g. if the cap is replaced quickly after removal), the control unit re-enters the "cap on" state (104). However, if the cap is not replaced within a predetermined time, the control unit enters a reset state (102) and the timer is reset and held at zero as described above, and all segments of the LCD blink.

The present invention provides a simple, easy to use and cost effective replaceable cap for a drug delivery device by which a patient can confirm the time elapsed since the last dose occurred. The present invention does not require the user to carry any additional devices, as the cap simply replaces the existing cap provided with the medicating device. No specific instructions need to be followed, no timing schemes using a flash or other non-numeric indicator need to be known and remembered, no patient need change the procedure of using the medicated device. Anyone familiar with the digital clock (who should include very young and very frail) can easily use the cap. Furthermore, because the internal dimensions of the replaceable cap are selected to match the internal dimensions of the original cap being replaced, the cap of the present invention has the same snap-fit or push-fit feel as the original cap, and the switch mechanism does not interfere in any way with the degree of security with which the cap is fitted to the drug delivery device. The cap top and the cap bottom can be made by substantially two-part injection moulding and the cap can be moulded very cost-effectively as there is no need to mould moving parts into the cap. Since the chamber in which the control unit is installed is standard for all different types of caps, the control unit can be mass produced, so that the cost of the cap is further reduced.

While the invention has been described with reference to specific embodiments, it will be understood that the invention is not limited to the described embodiments and that modifications may be made without departing from the scope of the invention. For example, the switch mechanism need not include a leaf spring but may include a dome switch or a conductive elastomeric switch. In other embodiments, the capacitive sensor can detect the presence of the front of the insulin pen without the need for physical contact or moving parts, which would facilitate the sealing of the electronic parts. A light sensor may also be used, which emits a light beam to be interrupted by the insulin pen through the inner surface of the reflective cap or by sensing ambient light. The replaceable cap of the present invention may be used with other types of medicating devices, for example, epinephrine auto-injectors, antiretroviral pens, or other medicating devices that utilize replaceable caps. The timer unit need not count but may count down, indicating the remaining time for the next dose to expire.

Claims (15)

1. A replaceable cap for a transcutaneous liquid medicating device, comprising an elongated hollow body having a first open end, which can be disposed on a front portion of the medicating device, and a second closed end, opposite to the first open end, from which liquid is medicated, the cap being removably received on the medicating device, wherein cap body comprises a cavity, which houses a timer unit coupled to a switch mechanism, which displays time counted by the timer unit on an outer surface of the cap body, and a timer display unit, wherein the switch mechanism is engaged by an engagement of a surface of the front portion of the medicating device when the cap is placed on the medicating device and when the cap is removed from the medicating device, the switch mechanism is released and operation of the switch causes the timer unit to reset immediately or after a predetermined period of time such that the time since the timer unit was last reset indicates the time elapsed since the applicator device was last used, wherein the elongate hollow body of the cap comprises two main parts, the two main parts being injection moulded plastics and being connected to each other to form the cap, the cap having the cavity at least partially defined between the two main parts, wherein the two main parts clamp the timer unit and the switch between the two main parts.

2. The replaceable cap for a transdermal liquid-dosing device of claim 1, wherein the switch is in the form of an electromechanical switch that protrudes into the interior of the cap body so as to fit the outer surface of the liquid-dosing device.

3. The replaceable cap for a transdermal liquid medicating device of claim 1, wherein the two main portions are a cap top portion and a cap bottom portion, the cap top portion having a window through which the timer display unit is visible and a flange having a free end extending toward the first open end to form a pocket clip, the cap bottom portion forming a majority of the length of the elongated hollow body.

4. The replaceable cap for a transdermal liquid medicating device of claim 1, wherein the second closed end has a battery compartment disposed therein with a lid mounted in place to securely hold a battery in the battery compartment.

5. The replaceable cap for a transdermal liquid medicating device of claim 4, wherein the cap can be color-coded to enable a user to match the cap with a particular medicating device to distinguish between different medicating devices.

6. The replaceable cap for a transdermal liquid medicating device of claim 4, wherein a removable non-conductive film is initially disposed between the battery and associated battery contacts, the film extending through a slit in the cap body and across an outer surface of the timer display unit to terminate in a protruding tongue that can be grasped by a user to pull the film out of the battery compartment to enable the battery to engage the battery contacts prior to use of the cap.

7. The replaceable cap for a transdermal liquid drug delivery device of claim 1, wherein the timer display unit is a low cost four digit digital Liquid Crystal Display (LCD), the timer unit is configured to count from zero, the timer is reset to zero by releasing the switch mechanism, and the timer unit is configured to count minutes using the first two digits and count seconds using the last two digits, and then count hours using the first two digits and count minutes using the next two digits within the first 59 minutes and 59 seconds elapsed since the drug delivery device was last used.

8. The replaceable cap for a transdermal liquid dosing device of claim 1 wherein the timer unit includes electronic circuitry on a Printed Circuit Board (PCB) and the timer unit, timer display unit and switch mechanism are assembled together as a single control unit in the chamber.

9. The replaceable cap for a transdermal liquid medicating device of claim 8, wherein the cavity is of a standard size such that the same control unit can be mounted to a variety of different caps, wherein each cap has an adjustable inner surface size to fit a particular type of medicating device, thus the control unit can be mass produced for all caps as economies of scale increase.

10. The replaceable cap for a transdermal liquid-dosing device of claim 2, wherein the switch mechanism comprises a spring tab protruding into the interior of the cap body and mounted against the electromechanical switch such that the spring tab activates the electromechanical switch when the spring tab is bent toward the cavity.

11. The replaceable cap for a transdermal liquid medicating device of claim 10, wherein the spring leaf is oriented such that the spring leaf has a fixed end closer to the first open end of the cap and a free end closer to the second closed end of the cap, such that the act of inserting the front portion of the medicating device into the cap causes the spring leaf to bend toward the lumen without the free end hooking onto any feature of the front portion of the medicating device.

12. The replaceable cap for a transdermal liquid medicating device of claim 10, wherein the spring leaf is made of spring steel and is sufficiently curved such that different shaped fronts of different medicating devices will all sufficiently engage the spring leaf to activate the switch.

13. The replaceable cap for a transdermal liquid dosing device of claim 1 wherein the timer unit resets after a predetermined period of time has elapsed, the predetermined period of time being between 5 and 12 seconds to prevent the timer unit from being reset if the user only removes the cap briefly.

14. The replaceable cap for a transdermal liquid medicating device of claim 1, wherein the internal dimensions of the replaceable cap body are selected to match the internal dimensions of an existing cap originally provided with the medicating device, such that the replaceable cap provides the same or very similar push-in or snap-fit on the medicating device as an existing cap.

15. The replaceable cap for a transdermal liquid dosing device of claim 1 wherein the dosing device is a disposable insulin pen comprising a reservoir and a hypodermic needle disposed at the front of the dosing device and the replaceable cap is also disposable but can be used continuously with respect to at least several disposable insulin pens.