Stopping phenformin treatment in a diabetic clinic.

Phenformin was stopped in 35 patients attending a diabetic clinic. In 4 patients where phenformin alone had been used, subsequent diabetic control was easily maintained with diet or a sulphonylurea. Thirty-one patients had been taking phenformin with a sulphonylurea and 17 (55%) later required insulin. Larger doses of a sulphonylurea were usually needed in the other patients. It is suggested that metformin is probably the biguanide of choice now and should be considered in carefully selected diabetics.