6.1.2 Antidiabetic drugs
Oral antidiabetic drugs are used for the treatment of type 2 diabetes mellitus. They should be prescribed only if the patient fails to respond adequately to at least 3 months’ restriction of energy and carbohydrate intake and an increase in physical activity. They should be used to augment the effect of diet and exercise, and not to replace them.
For patients not adequately controlled by diet and oral hypoglycaemic drugs, insulin may be added to the treatment regimen or substituted for oral therapy. When insulin is added to oral therapy, it is generally given at bedtime as isophane insulin, and when insulin replaces an oral regimen it is generally given as twice-daily injections of a biphasic insulin (or isophane insulin mixed with soluble insulin). Weight gain and hypoglycaemia may be complications of insulin therapy but weight gain may be reduced if the insulin is given in combination with metformin.
Pregnancy and breast-feeding
During pregnancy, women with either pre-existing or gestational diabetes may be treated with metformin [unlicensed use], either alone or in combination with insulin (section 6.1.1). Women with gestational diabetes should discontinue hypoglycaemic treatment after giving birth. Metformin can be continued during breast-feeding for those with pre-existing diabetes.
Other oral hypoglycaemic drugs, including sulphonylureas, are contra-indicated in pregnancy (see also Appendix 4) and in breast-feeding (Appendix 5).