Persistent Hyperinsulinemia Following High-Dose Insulin Therapy: A Case Report

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.

Zinc Phosphide Poisoning: From A to Z

Zinc phosphide is a rodenticide that is used in agricultural, urban and industrial environments in México. After ingestion, it reacts with hydrochloric acid, hydrolyzing into phosphine. It causes cellular hypoxia via mitochondrial toxicity, resulting in multiple organ dysfunction and death. There is no antidote or specific treatment for zinc phosphide toxicity. We present the case of a 45-year-old female who ingested zinc phosphide with suicidal intent. On arrival at the emergency department, she had multisystemic disorders. Supportive care, decontamination and antidotal therapy were initiated. Subsequently, she evolved to clinical improvement with a resolution of the biochemical abnormalities of tissue hypoperfusion. She was discharged on day 7 without complications. In this review, we provide updated therapeutic options and discuss their specific pathophysiological basis.

Variability in insulin pharmacokinetics following high-dose insulin therapy

INTRODUCTION

High dose insulin (HDI) therapy for cardiogenic shock from acute poisoning can be complicated by treatable hypoglycemia which persists following poisoning recovery. Glucose requirements post-HDI reflect supraphysiological insulin plasma concentration. A publication reported a patient treated with HDI with plasma insulin concentrations >1000 µU/mL and elimination half-life 10-18 h requiring intravenous glucose replacement for >5 days. We report two cases treated with HDI (Actrapid; soluble or regular insulin) with shorter elimination half-lives.

CASE REPORTS

A man ingesting diltiazem received HDI for approximately 60 h (maximum dose 10 U/kg/h) and supplemental intravenous dextrose for 44 h post-HDI. Post-HDI the maximum measured plasma insulin concentration was 6345 µU/mL and elimination half-life 5.5 h. A man ingesting propranolol received HDI for approximately 12 h (maximum dose 1.5 U/kg/h) and supplemental intravenous dextrose for 4 h post-HDI. Post-HDI the maximum measured plasma insulin concentration was 368 µU/mL and elimination half-life 2.2 h.

DISCUSSION

Markedly different insulin pharmacokinetics post-HDI is observed in two cases and a previously published report, and factors contributing to the interpatient differences are poorly defined. This pharmacokinetic variability impacts on the severity and duration of treatable hypoglycemia post-HDI. Analytical factors impacting on the measured plasma insulin concentrations include appropriate sample dilution and differing analytical specificity for the type of insulin.