VA Class:AP200
Pyrantel pamoate is a pyrimidine-derivative anthelmintic agent.
Nematode (Roundworm) Infections
Pyrantel pamoate is used in the treatment of several nematode (roundworm) infections, including ascariasis†, 106 enterobiasis,102, 105, 106 and intestinal hookworm infections†.102, 105, 108, 109 Efficacy of the drug in the treatment of helminthic infections may vary as a function of GI transit time and the degree of infection. Cure rates may be lower than average in patients who have massive infections and/or hypermotility of the GI tract.
Pyrantel pamoate is used for the treatment of enterobiasis caused by Enterobius vermicularis (pinworm infection),102, 105, 106, 108, 109 and may be used for self-medication of enterobiasis.100, 103, 108, 109 The drug has produced cure rates of 90-100% when used for the treatment of enterobiasis. Pyrantel pamoate, mebendazole, and albendazole are recommended as the drugs of choice for the treatment of enterobiasis.102, 105
Pyrantel pamoate has been used in the treatment of ascariasis† caused by Ascaris lumbricoides 106 and has produced cure rates of 85-100%. However, albendazole, ivermectin, and mebendazole are recommended as the drugs of choice for the treatment of ascariasis.102, 105
Pyrantel pamoate is used for the treatment of intestinal hookworm infections caused by Ancylostoma duodenale † or Necator americanus †, 102, 105 reportedly producing cure rates of 92-96% and 48-93%, respectively. The drugs of choice for these intestinal hookworm infections are albendazole, mebendazole, or pyrantel pamoate.102, 105
Pyrantel pamoate, like albendazole or mebendazole, is considered a drug of choice for the treatment of eosinophilic enterocolitis† caused by Ancylostoma caninum (dog hookworm).102 When indicated, endoscopic worm extraction also is considered a treatment of choice for eosinophilic enterocolitis.102
Pyrantel pamoate or albendazole may be effective for the treatment of oesophagostomiasis† caused by Oesophagostomum bifurcum .102
Pyrantel pamoate has been used with variable results for the treatment of trichostrongyliasis†. Pyrantel pamoate is considered the drug of choice for the treatment of Trichostrongylus infections; albendazole and mebendazole are alternatives.102
Pyrantel pamoate is considered the drug of choice for the treatment of infections caused by Moniliformis moniliformis † (thorny-headed worm).102
Pyrantel pamoate is administered orally.108, 109
Pyrantel pamoate may be taken without regard to meals,108, 109 and may be taken or mixed with milk or fruit juice.108, 109
The oral suspension should be shaken well prior to using.108
Special diet, fasting, or purgation prior to administration of pyrantel pamoate is not necessary. Patients should be advised of hygienic precautions needed to minimize reinfection.
Patients undertaking self-medication of enterobiasis should be provided information supplied by the manufacturer that describes dosage, hygienic precautions needed to minimize reinfection, symptoms of pinworm infections, the worm's life cycle, and how to locate and identify the worm. The presence of pinworms should be confirmed visually before initiating self-medication .100, 108, 109
Dosage of pyrantel pamoate is expressed in terms of pyrantel.108, 109
Nematode (Roundworm) Infections
For the treatment of enterobiasis caused by Enterobius vermicularis (pinworm infection), the usual dosage of pyrantel pamoate in adults and children is 11 mg (of pyrantel) per kg (maximum 1 g), given as a single dose; the dose should be repeated after 2 weeks.102
For self-medication of enterobiasis in adults and children 2 years of age or older, pyrantel pamoate is given as a single dose of 11 mg (of pyrantel) per kg (maximum 1 g).108, 109 A repeat course of treatment should be undertaken only under the direction of a clinician.100, 108, 109
Some clinicians recommend that all household contacts of patients with enterobiasis receive treatment, especially in situations in which multiple or repeated symptomatic infections occur, since such contacts commonly also are infected.102, 105
For the treatment of intestinal hookworm infections caused by Ancylostoma duodenale † or Necator americanus †, the recommended dosage of pyrantel pamoate for adult and pediatric patients is 11 mg (of pyrantel) per kg (maximum 1 g) once daily for 3 consecutive days.102 A repeat stool examination (using a concentration technique) for eggs of A. duodenale or N. americanus should be performed 2 weeks after treatment and the regimen should be repeated if results are positive.105
For the treatment of eosinophilic enterocolitis† caused by Ancylostoma caninum , the recommended dosage of pyrantel pamoate for adult and pediatric patients is 11 mg (of pyrantel) per kg (maximum 1 g) once daily for 3 consecutive days.102
For the treatment of trichostrongyliasis†, the usual dosage of pyrantel pamoate in adults and children is 11 mg (of pyrantel) per kg (maximum 1 g) given as a single dose.102
For the treatment of infections caused by Moniliformis moniliformis † (thorny-headed worm), the usual dosage of pyrantel pamoate in adults and children is 11 mg (of pyrantel) per kg given as a single dose; this dosage should be repeated twice at 2-week intervals for a total of 3 doses.102
Adverse effects of pyrantel pamoate usually are mild, infrequent, and transient.100 Adverse GI effects, including nausea,108, 109 vomiting,108, 109 tenesmus, anorexia, diarrhea,108, 109 abdominal cramps,108, 109 and gastralgia may occur. Adverse GI effects may be related to expulsion of the helminths.101
Other less frequent adverse effects of pyrantel include headache,108, 109 dizziness,108, 109 drowsiness, insomnia, rash, fever, and weakness. Transient increases in serum concentrations of AST (SGOT) have been reported in a small number of patients receiving the drug.100 Although ototoxicity, optic neuritis, and hallucinations with confusion and paresthesia have been reported rarely, evidence of a causal relationship to the drug is lacking.101
Precautions and Contraindications
Pyrantel pamoate is contraindicated in patients who are hypersensitive to the drug.
Patients should be advised to contact a clinician if abdominal cramps, nausea, vomiting, diarrhea, headache, or dizziness persist after taking pyrantel pamoate.100, 108, 109 Patients using the drug for self-medication of enterobiasis should be advised to contact a clinician if worms other than pinworms are present before or after treatment with the drug or if symptoms of enterobiasis persist.100, 108, 109
Because minimal, transient increases in serum concentrations of AST (SGOT) have been reported in some patients receiving pyrantel pamoate, the drug should be used with caution in patients with preexisting liver dysfunction.100 Patients with liver disease should not use pyrantel pamoate for self-medication of enterobiasis unless directed by a clinician.108, 109
Pyrantel pamoate should be used with caution in patients with severe malnutrition or anemia. Ideally, supportive therapy is indicated for anemic, dehydrated, or malnourished patients prior to administration of the drug.
Because of limited experience with pyrantel pamoate in children younger than 2 years of age, the drug should be used in such children only when the potential benefits justify the possible risks.105
In clinical studies in children receiving a single 11-mg/kg dose of the drug, serum AST concentrations increased transiently in less than 2% of patients; however, in undocumented cases in whom baseline values were not determined, small elevations of AST 24-48 hours after a dose were reported more frequently.101
Reproduction studies in animals using pyrantel pamoate have not revealed evidence of harm to the fetus. There also was no evidence of impaired fertility in rats.101 There are no adequate and controlled studies to date using pyrantel pamoate in pregnant women,100 and the drug should be used during pregnancy only when clearly needed.
Pregnant women considering self-medication with the drug should do so only under the direction of a clinician.100, 108, 109
Piperazine (no longer commercially available in the US) and pyrantel pamoate have antagonistic modes of action and should not be administered concomitantly.
Pyrantel pamoate does not appear to be associated with substantial risk of toxicity following acute oral overdose.101 No evidence of adverse effect or morphologic change attributable to the drug was apparent in rats receiving oral dosages up to 500 mg/kg daily for 30 days, although slight reductions in growth rate and food consumption were observed in rats receiving 600 mg/kg daily for 13 weeks.101 Although 2 children have died while receiving pyrantel pamoate, death in these children was not attributable to the drug.100, 101
Pyrantel pamoate is a depolarizing neuromuscular blocking agent that exerts its anthelmintic effect via release of acetylcholine and inhibition of cholinesterase, resulting in stimulation of ganglionic (nicotinic) receptors of susceptible helminths. Unlike piperazine, pyrantel produces depolarization of the muscle membrane and increases spike-discharge frequency. The paralyzed worms are expelled from the GI tract by normal peristalsis.
Pyrantel is active against Enterobius vermicularis (pinworm), Ascaris lumbricoides (roundworm), Ancylostoma duodenale (hookworm), Necator americanus (hookworm), and Trichostrongylus orientalis (hairworm).
Pyrantel pamoate is poorly absorbed from the GI tract. Following a single oral pyrantel dose of 11 mg/kg, peak plasma concentrations of 50-130 ng/mL occur within 1-3 hours.
The absorbed drug is partially metabolized in the liver. Approximately 50% of an oral dose of pyrantel pamoate is excreted unchanged in feces and about 7% is excreted in urine as unchanged drug and its metabolites containing N -methyl-1,3-propanediamine.
Pyrantel pamoate is a pyrimidine-derivative anthelmintic agent. Each 290 mg of pyrantel pamoate is approximately equivalent to 100 mg of pyrantel base. Pyrantel pamoate occurs as a yellow to tan solid and is practically insoluble in water and in alcohol. The commercially available pyrantel pamoate oral suspension has a pH of 4.5-6.
Commercially available pyrantel pamoate oral suspension should be stored in tight, light-resistant containers at a temperature less than 30°C.
Excipients in commercially available drug preparations may have clinically important effects in some individuals; consult specific product labeling for details.
Please refer to the ASHP Drug Shortages Resource Center for information on shortages of one or more of these preparations.
Routes | Dosage Forms | Strengths | Brand Names | Manufacturer |
|---|---|---|---|---|
Oral | Suspension | 250 mg (of pyrantel) per 5 mL* | ||
Pyrantel Pamoate Suspension | ||||
Reese's® Pinworm Medicine | ||||
Tablets | 62.5 mg (of pyrantel) | Reese's® Pinworm Caplets® | Reese |
* available from one or more manufacturer, distributor, and/or repackager by generic (nonproprietary) name
Only references cited for selected revisions after 1984 are available electronically.
100. Food and Drug Administration. Anthelmintic drug products for over-the-counter human use; final monograph. Fed Regist . 1986; 51:27756-60.
101. Food and Drug Administration. Anthelmintic drug products for over-the-counter human use; establishment of a monograph. Fed Regist . 1980; 45:59540-8.
102. Anon. Drugs for parasitic infections. From the Medical Letter website. 2008 Aug. [Web]
103. Food and Drug Administration. Over-the-counter drug products; final monographs for antiemetic, antitussive, bronchodilator, and antihelmintic drug products; updating and technical changes; final rule. Fed Regist . 1988; 53:35808-10.
105. American Academy of Pediatrics. 2006 Red Book: Report of the Committee on Infectious Diseases. 27th ed. Elk Grove Village, IL: American Academy of Pediatrics; 2006.
106. Liu LX. Strongyloidiasis and other intestinal nematode infections. Infect Dis Clin North Am . 1993; 7:655-82. [PubMed 8254165]
107. Briggs GG, Freeman RK, Yaffe SJ. Drugs in pregnancy and lactation. 8th ed. Baltimore, MD: Williams & Wilkins; 2008:1559.
108. Reese. Reese's pinworm medicine (pyrantel pamoate) prescribing information. Cleveland, OH.
109. Reese. Reese's pinworm caplets (pyrantel pamoate) prescribing information. Cleveland, OH.