Serum and urinary concentrations of sulfonylureas were measured in 125 diabetic patients over periods of eight to eighteen months. The concentrations were dose related. They varied between individuals but tended to remain constant in the same person. They also tended to vary inversely with body weight. Acetohexamide concentration increased with the number of doses given daily. The per cent of urinary recovery of each drug was unrelated to dosage.
The response to therapy was graded and ranges of therapeutically effective serum concentrations determined. A delayed response was observed in some patients, and failure to respond occurred in others despite high serum concentrations. Presumed failure to take the prescribed drugs was seen in five patients.