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Section IVOther important drugsInsulinA chainB chainC peptideProinsulinFigure 24.1.Convertion of pro-insulin to insulin and C peptide. (.....=disulphide bridge)as short-, medium- or long-acting. In the UK the standard insulin concentration is
100 units.ml−^1.
Short-acting – this is a simple solution of insulin that may be administered intra-
venously for rapid effect. Following subcutaneous injection its duration of action
may extend for up to 8 hours.
Medium- and long-acting – when insulin is complexed with zinc or protamine, or
produced as crystals rather than in its amorphous form, its solubility decreases
and its absorption prolonged. This extends its duration of action to 16–35 hours.Side effects
When calorie intake is insufficient hypoglycaemia will ensue. If untreated this will
lead to coma and death. All insulins are immunogenic but despite this immunological
resistance is rare. Beef insulin has three different amino acids compared to human
insulin while pork insulin has only one; the latter is therefore less immunogenic.
Localized lipodystrophy is also rare.Sulphonylureas
Twogenerations of sulphonylureas exist and have slightly different characteristics:
First generation – chlorpropamide, tolbutamide, acetohexamide.
Second generation – glibenclamide, gliclazide, glipizide.