OVERDOSAGE
Signs and Symptoms –
The symptoms of toxicity from papaverine hydrochloride often result from vasomotor instability and include nausea, vomiting, weakness, central nervous system depression, nystagmus, diplopia, diaphoresis, flushing, dizziness, and sinus tachycardia. In large overdoses, papaverine is a potent inhibitor of cellular respiration and a weak calcium antagonist. Following an oral overdose of 15 g, metabolic acidosis with hyperventilation, hyperglycemia, and hypokalemia have been reported. No information on toxic serum concentrations is available.
Following intravenous overdosing in animals, seizures, tachyarrhythmias, and ventricular fibrillation have been reported. The oral median lethal dose in rats is 360 mg/kg.
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 Physician’s Desk Reference (PDR). In managing overdosage, consider the possibility of multiple drug overdoses, interaction among drugs, and unusual drug kinetics in your patient.
Protect the patient’s airway and support ventilation and perfusion. Meticulously monitor vital signs, blood gases, blood chemistry values, and other variables.
If convulsions occur, consider diazepam, phenytoin, or phenobarbital. If the seizures are refractory, general anesthesia with thiopental or halothane and paralysis with a neuromuscular blocking agent may be necessary.
For hypotension, consider intravenous fluids, elevation of the legs, and an inotropic vasopressor, such as dopamine or norepinephrine (levarterenol). Theoretically, calcium gluconate may be helpful in treating some of the toxic cardiovascular effects of papaverine; monitor the ECG and plasma calcium concentrations.
Forced diuresis, peritoneal dialysis, hemodialysis, or charcoal hemoperfusion have not been established as beneficial for an overdose of papaverine hydrochloride.
|