the United Kingdom Prospective Diabetes Study Group (UKPDS) has pointed out that majority of type 2 diabetes patients will experience progressive pancreatic beta cell dysfunction even when their diabetes control is excellent (1)
so type 2 diabetics may eventually require treatment with insulin when oral hypoglycaemic medication is no longer effective
a straight swap to insulin treatment is usual if the maximal therapy with non-insulin treatments have been reached
according to estimations in UK general practice, only 50% of patients who require insulin due to failure of oral medication will receive it within 5 years o the average time taken from beginning treatment with the last oral agent to beginning insulin therapy is around 8 years (2)
in the case of overweight patients taking metformin, then treatment with metformin may be continued - this is because metformin may attenuate weight gain resulting from the introduction of insulin therapy
insulin therapy and a sulphonylurea may decrease the amount of insulin actually required and enhance the use of a single night-time dose but overall the clinical advantages of this combination are small (3)
the average weight gain resulting from introduction of insulin therapy is 4 kg - however some patients may have a marked increase in weight after onset of insulin therapy
in a comprehensive review of combination therapies with insulin in type 2 diabetes Yki-Jarvinen suggests an algorithm for starting insulin in an insulin naive type 2 diabetic patient who is on maximal oral hypoglycaemic therapy. In this algorithm she suggests stopping sulphonylurea treatment and continuation of metformin at a dose of 2g per day in combination with insulin treatment (4). If the patient is not on a dose of 2g per day when conversion to insulin occurs then the dose of metformin should be increased by 500mg per week until a metformin dose of 2g per day is achieved (5)
in consideration of combination of insulin and an oral hypoglycaemic agent in type 2 diabetes:
well-designed trials indicate that glargine and NPH bedtime insulin are similarly effective in combination with oral antidiabetic agents, with a superior hypoglycaemic profile for glargine (6)
one review concluded that once-daily glargine insulin plus metformin (> 2 g per day), in suitable patients, may be the optimum combination (6)
a systematic review analysing the use of bedtime NPH insulin and oral hypoglycaemic agents concluded that:
bedtime NPH insulin combined with oral hypoglycaemic agents provides comparable glycaemic control to insulin monotherapy and is associated with less weight gain if metformin is used (7)
in consideration as to whether to initiate once or twice daily insulin in type 2 diabetic patients:
there is study evidence that (8) in subjects with type 2 diabetes poorly controlled on oral hypoglycaemic agents, initiating insulin therapy with twice-daily biphasic insulin aspart 70/30 (prebreakfast and presupper) BIAsp 70/30 was more effective in achieving HbA(1c) targets than once-daily glargine, especially in subjects with HbA(1c) >8.5%.
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