Papaverine Drug Information

Papaverine is recommended in various conditions accompanied by spasm of smooth muscle, such as vascular spasm associated with acute myocardial infarction (coronary occlusion), angina pectoris, peripheral and pulmonary embolism, peripheral vascular disease in which there is a vasospastic element, or certain cerebral angiospastic states; and visceral spasm, as in ureteral, biliary, or gastrointestinal colic.

Papaverine Hydrochloride may be administered intravenously or intramuscularly. The intravenous route is recommended when an immediate effect is desired, but the drug must be injected slowly over the course of 1 or 2 minutes to avoid uncomfortable or alarming side effects. Parenteral administration of papaverine hydrochloride in doses of 1 to 4 mL is repeated every 3 hours as indicated.

In the treatment of cardiac extrasystoles, 2 doses may be given 10 minutes apart.

The following side effects have been reported: general discomfort, nausea, abdominal discomfort, anorexia, constipation or diarrhea, skin rash, malaise, vertigo, headache, intensive flushing of the face, perspiration, increase in the depth of respiration, increase in heart rate, a slight rise in blood pressure, and excessive sedation. Hepatitis, probably related to an immune mechanism, has been reported infrequently. Rarely, this has progressed to cirrhosis.

Usage In Pregnancy - Pregnancy Category C - No teratogenic effects were observed in rats when papaverine hydrochloride was administered subcutaneously as a single agent. It is not known whether papaverine can cause fetal harm when administered to a pregnant woman or can affect reproduction capacity. Papaverine Hydrochloride should be given to a pregnant woman only if clearly needed.

Usage In Children - Safety and effectiveness in children have not been established.

Intravenous injection of papaverine is contraindicated in the presence of complete atrioventricular heart block. When conduction is depressed, the drug may produce transient ectopic rhythms of ventricular origin, either premature beats or paroxysmal tachycardia. Papaverine Hydrochloride is not indicated for the treatment of impotence by intracorporeal injection.

The intracorporeal injection of papaverine hydrochloride has been reported to have resulted in persistent priapism requiring medical and surgical intervention.

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.