OVERDOSE
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.