Signs and Symptoms — If overdosage occurs, nausea, vomiting, gastric hypotonicity, and diarrhea would be expected without causing consequential toxicity.
Intravenous administration of glucagon has been shown to have positive inotropic and chronotropic effects. A transient increase in both blood pressure and pulse rate may occur following the administration of glucagon. Patients taking β-blockers might be expected to have a greater increase in both pulse and blood pressure, an increase of which will be transient because of glucagon's short half-life. The increase in blood pressure and pulse rate may require therapy in patients with pheochromocytoma or coronary artery disease.
When glucagon was given in large doses to patients with cardiac disease, investigators reported a positive inotropic effect. These investigators administered glucagon in doses of 0.5 to 16 mg/hour by continuous infusion for periods of 5 to 166 hours. Total doses ranged from 25 to 996 mg, and a 21-month-old infant received approximately 8.25 mg in 165 hours. Side effects included nausea, vomiting, and decreasing serum potassium concentration. Serum potassium concentration could be maintained within normal limits with supplemental potassium.
The intravenous median lethal dose for glucagon in mice and rats is approximately 300 mg/kg and 38.6 mg/kg, respectively.
Because glucagon is a polypeptide, it would be rapidly destroyed in the gastrointestinal tract if it were to be accidentally ingested.
Treatment — To obtain up-to-date information about the treatment of overdose, a good resource is your certified Regional Poison Control Center. Telephone numbers of certified poison control centers are listed in the Physicians' Desk Reference (PDR). In managing overdosage, consider the possibility of multiple drug overdoses, interaction among drugs, and unusual drug kinetics in your patient.
In view of the extremely short half-life of glucagon and its prompt destruction and excretion, the treatment of overdosage is symptomatic, primarily for nausea, vomiting, and possible hypokalemia.
If the patient develops a dramatic increase in blood pressure, 5 to 10 mg of phentolamine mesylate has been shown to be effective in lowering blood pressure for the short time that control would be needed.
Forced diuresis, peritoneal dialysis, hemodialysis, or charcoal hemoperfusion have not been established as beneficial for an overdose of glucagon; it is extremely unlikely that one of these procedures would ever be indicated.