Insulin concentrations following termination of high-dose insulin euglycemic therapy.

Introduction: High-dose insulin therapy is used in patients with calcium channel blocker and beta-adrenergic antagonist overdoses. The pharmacokinetics of insulin are scantly reported following high-dose insulin therapy. We present two cases of persistently elevated insulin concentrations following high-dose insulin therapy.

Case Reports: A 50-year-old woman and a 45-year-old man experienced hypotension after overdosing on amlodipine and atenolol. They were treated with high-dose insulin therapy for 54 hours at 2 units/kilogram/hour and 48 hours at 10 units/kilogram/hour, respectively. Following termination, serum insulin elimination was studied. Insulin concentrations remained greater than 1,000 µU/mL (fasting reference 2.6-24.9 µU/mL) for longer than 4 hours (case 1) and 11 hours (case 2) and greater than 300 µU/mL for longer than 8 hours and 21 hours, respectively. Insulin concentrations decreased with apparent first-order elimination half-lives of 13.0 hours and 6.0 hours.

Discussion: Following high-dose insulin therapy, insulin concentrations remained elevated for longer than expected based on normal pharmacokinetics in therapeutic dosing. Three previous cases reported insulin half-lives of between 2.2 hours and 18.7 hours. The current cases add to the existing data that insulin has a variable but prolonged half-life following high-dose insulin therapy.

Conclusions: These findings suggest that patients are at prolonged risk of hypoglycemia following cessation of high-dose insulin infusions.