Pyrantel

Pyrantel is an anthelmintic drug used to treat intestinal nematode infections in humans and animals. It exists in salt forms such as pyrantel tartrate and pyrantel pamoate and is taken by mouth.

Mechanism and pharmacology: Pyrantel acts as a nicotinic acetylcholine receptor agonist in nematodes, causing depolarizing neuromuscular paralysis. The impaired parasite loses its ability to maintain attachment to the intestinal wall and is expelled in the feces. It is poorly absorbed from the gastrointestinal tract, so most of the drug’s activity is local to the gut with limited systemic exposure.

Clinical uses and spectrum: Pyrantel is effective against several intestinal nematodes, including Ascaris lumbricoides, hookworms (Ancylostoma, Necator), and Enterobius vermicularis (pinworm). It is not active against cestodes (tapeworms) or trematodes (flukes). In humans, dosing is typically a single oral dose of about 11 mg/kg (up to a maximum of 1 g), with a second dose after 2–3 weeks in certain infections or when persistent symptoms are present. In veterinary medicine, pyrantel is widely used for dogs, cats, foals, and other animals, with species- and weight-specific dosing.

Safety and regulatory status: Pyrantel is generally well tolerated. Reported adverse effects are usually mild and may include nausea, vomiting, abdominal cramps, and diarrhea; hypersensitivity reactions are rare. It is contraindicated in individuals with a known hypersensitivity to the drug. Pregnancy and lactation considerations should be guided by a healthcare professional.

Availability: It is available over the counter in many countries in pyrantel tartrate or pyrantel pamoate formulations for humans, and is also used in veterinary products.