Newer Insulin Delivery Devices

NEWER INSULIN DELIVERY DEVICES

A number of innovations have been made to improve ease and accuracy of insulin administration as well as to achieve tight glycaemia control. These are:

1. Insulin syringes Prefilled disposible syringes contain specific types or mixtures of regular and modified insulins.

2. Pen devices Fountain pen like: use insulin cartridges for s.c. injection through a needle. Preset amounts (in 2 U increments) are propelled by pushing a plunger; convenient in carrying and injecting.

3. Inhaled insulin Recently, an inhaled human insulin preparation has been marketed in Europe and the USA. The fine powder is delivered through a nebulizer; absorption is rapid. Peak action occurs at ~2 hours and duration of action is 6–7 hours. It is used to control mealtime glycaemia, but is not suitable for round the clock basal effect. Less than 10% of inhaled insulin is absorbed. Pulmonary fibrosis and other complications are apprehended on long-term use.

4. Insulin pumps Portable infusion devices connected to a subcutaneously placed cannula: provide ‘continuous subcutaneous insulin infusion’ (CSII). Only regular insulin is used. They can be programmed to deliver insulin at a low basal rate (approx. 1 U/hr) and premeal boluses (4– 15 times the basal rate) to control postprandial glycaemia. Though, theoretically more appealing, no definite advantage of CSII over multidose s.c. injection has been demonstrated. Moreover, cost, strict adherence to diet, exercise, care of the device and cannula, risk of pump failure, site infection, are too demanding on the patient.

5. Implantable pumps Consist of an electromechanical mechanism which regulates insulin delivery from a percutaneously refillable reservoir. Mechanical pumps, fluorocarbon propellant and osmotic pumps are being developed.

6. External artificial pancreas This is a micro-processor controlled device connected through i.v. lines, which measures blood glucose and then infuses appropriate amounts of insulin in a continuous feedback manner. Its size, cost and other problems limit use to only research situations.

7. Other routes of insulin delivery Intraperitoneal, oral (by complexing insulin into liposomes or coating it with impermeable polymer) and rectal routes are being tried. These have the advantage of providing higher concentrations in the portal circulation, which is more physiological.