Medical treatment of several illnesses requires continuous drug infusion into various body compartments, such as subcutaneous and intra-venous injections. Diabetes mellitus patients, for example, require the administration of varying amounts of insulin throughout the day to control their blood glucose levels. In recent years, ambulatory portable insulin infusion pumps have emerged as a superior alternative to multiple daily syringe injections of insulin. These pumps, which deliver insulin at a continuous basal rate as well as in bolus volumes, were developed to liberate patients from repeated self-administered injections, and allow them to maintain a near-normal daily routine. Both basal and bolus volumes must be delivered in precise doses, according to individual prescription, since an overdose or under-dose of insulin could be fatal.
The 1st generation of portable infusion pumps disclosed “pager-like” devices with a reservoir contained within the device's housing. In such 1st generation devices, a long tube delivers insulin from the pump attached to a patient's belt to a remote insertion site. Both basal and bolus volume deliveries in these “pager-like” devices are controlled via a set of buttons provided on the device. Such devices are disclosed, for example, in U.S. Pat. Nos. 3,771,694, 4,657,486 and 4,498,843. These devices represent a significant improvement over multiple daily injections, but nevertheless, they all suffer from several major drawbacks, among which are the large size and weight of the device.
These uncomfortable bulky devices are rejected by the majority of diabetic insulin users, since they disturb regular activities, such as sleeping and swimming. In addition, the delivery tube excludes some optional remote insertion sites, like buttocks, arms and legs. To avoid the consequences of long delivery tube, a 2nd generation of pumps was proposed. As described in the prior art, the 2nd generation systems include a remote controlled skin adherable device with a housing having a bottom surface adapted for contact with the patient's skin, a reservoir disposed within the housing, and an injection needle adapted for communication with the reservoir. These skin adherable devices should be discarded every 2-3 days to avoid irritation and infection. This paradigm was described, for example, in U.S. Pat. Nos. 5,957,895, 6,589,229, 6,740,059, 6,723,072 and 6,485,461. However, these 2nd generation devices also have limitations: they are bulky and expensive. The high selling price is due to the high production and accessory costs. Moreover, such systems are expensive for users since they must be discarded every 2-3 days, including the relatively expensive components, such as the driving mechanism and other electronics.
Another major drawback of these 2nd generation skin adherable devices concerns the remote controlled drug administration. The users are totally dependent on the remote control and cannot initiate a bolus delivery if the remote control is not at hand, lost or has malfunctioned (practically, the patient cannot eat).
In some 2nd generation devices, a manual bolus button is disclosed, for example in U.S. Pat. No. 6,740,059, assigned to Insulet Corporation. When pressed, the spring loaded button moves a release finger away from a bolus delivery tube, thus enabling the delivery of a fixed amount of fluid from a bolus volume accumulator to the exit port of the device. This system has several drawbacks:                1. Unsafe: a life-threatening, unwanted bolus can be delivered by unintentional pressing of the button.        2. Not tailored to patient needs: a one size accumulator allows one bolus dose per button press. Thus, for example, if the accumulator volume is 0.2 units of insulin, a toddler that needs an average bolus dose of 1 unit has to press the button 5 times; however an adult that requires an average bolus dose of 6 units has to press the button 30 times. If, for example, the accumulator volume is 1 unit, the same adult needs 6 button presses but it limits most kids from using manual bolus delivery.        3. Prolonged manual bolus administration: the user has to wait for the accumulator to be refilled before the next consecutive bolus. For example, if 10 presses are required and the filling time is 0.5 minutes, the bolus administration time is 5 minutes.        4. Enlargement of the device's overall size: the employment of two reservoirs, one for basal delivery and one for bolus delivery, as well as two separate tubes and additional mechanical components (e.g. spring) requires enlargement of the device's overall size.        
A mechanical bolus button, suffering from the same abovementioned drawbacks, was also disclosed in U.S. Patent Application No. 2004/0162518, and U.S. Pat. No. 6,702,779 assigned to Becton, Dickinson and Company.
A 3rd generation skin adherable device was devised to avoid the cost issues of the 2nd generation and to extend patient customization. An example of such a device was described in co-owned/co-pending U.S. patent application Ser. No. 11/397,115 and International Patent Application No. PCT/IL06/001276, disclosers of which are incorporated herein by reference in their entireties. This 3rd generation device contains a remote control unit and a skin adherable dispensing patch unit (also referred to as “dispensing unit” or “dispensing patch”) that is comprised of two parts:                Reusable part—including the driving mechanism, fluid dispensing mechanism, electronics and other relatively expensive components.        Disposable part—including inexpensive, disposable components such as reservoir, tube and batteries, and an outlet port.        
This 3rd generation device/system provides a cost-effective skin adherable infusion device/system and allows diverse usage such as various reservoir sizes, various needle and cannula types, etc.
This 3rd generation skin adherable device, similarly to 2nd generation devices, can also be remotely controlled. However, it is desirable that manual initiation of fluid delivery will be possible when the remote control unit is not at hand (or not included), for at least one of basal and bolus drug delivery.