Pyrantel: A Safe and Effective Pinworm Treatment

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You might not have heard of it before, but pyrantel is a drug used to treat a serious condition suffered by millions of people every year. That condition is intestinal worms, including pinworms. The worms (helminths) cause symptoms ranging from abdominal pain and loss of appetite to dysentery. Pinworm infections can cause severe rectal itching and sleep disturbances, especially in young children. Drugs used to combat intestinal worms are known as anthelmintics.

Intestinal worms are transmitted through soil or hands that are contaminated with feces containing the eggs of worms. When a person or animal ingests the eggs, they hatch in the intestines and lead to illness. Worms can also be transmitted to humans by handling pets, such as dogs and cats that have not been treated for worms. Pet birds can also carry worms. Since intestinal worms can be transmitted from animals to people, they are considered "zoonotic" infestations.

According to the World Health Organization, soil-transmitted worm infestations afflict close to 1 billion people worldwide. About 10% of the population in the developing world is affected. In heavily infested areas, more than 50% of people can have intestinal worms. People in developing regions are at higher risk due to poor sanitation. Worm infestations can follow contact with household pets and other animals such as horses, cattle, sheep, goats, pigs, and llamas. Dogs and cats entering animal shelters are routinely treated for worms using pyrantel or other anthelmintic medications. Since an estimated 68% of households in the US own at least one pet, control of intestinal worms in pets has become an essential safeguard in preventing transmission to humans. In addition, children can pick up worm infestations by playing in dirt contaminated with feces and not washing their hands before eating or putting their hands in their mouths. If a person is diagnosed with intestinal worms, the entire household should be treated to prevent spread and reinfestation.

Pinworms are the most common roundworm to cause infection in children. Pinworms are tiny, thread-shaped organisms that are white in color. Humans are exposed to pinworms through oral contact, after contaminated fingers, clothes, or bedding allow for transfer of eggs into mouth. The eggs replicate and grow in the human gastrointestinal system and migrate through the intestines, finally exiting the human body through the anus. Female pinworms reposition their eggs to the skin surrounding the human anus. This process occurs primarily at night and results for the severe anal itching and disturbed sleep that is often associated with pinworm infection. Scratching of the affected area can cause additional spread of the eggs as well as reinfection of the same individual. While the worms themselves may be difficult to visualize, especially during daytime hours when they are less active, application and removal of sticky transparent tape to the affected skin may help reveal the presence of pinworm eggs. If eggs are present, treatment with pyrantel or a similar medication is recommended. Since pinworms are easily transferred from one individual to another by hand contact, it is recommended to treat both the affected individual as well as close contacts.

Pyrantel is a safe, effective, and inexpensive treatment for several types of intestinal worms, including pinworms. It has been in use since the mid-1970s. The most common form of pyrantel for human and veterinary use is pyrantel pamoate. The drug is FDA-approved for pinworm infestations. It is also effective for treatment of infections caused by other types of roundworms, hookworms, and whipworms. It is available without a prescription as a generic medication or under brand names such as Antiminth, Reese's Pinworm Medicine, Ascarel, and Pin-X. Pyrantel for veterinary use is found in products like Heartgard Plus, Strongid-T, and Nemex. Pyrantel cures worm infestations by paralyzing the worms, which then release from the intestines and travel out of the body in the stool.

Pyrantel has the advantage of being usually effective after a single oral dose. In some cases, when symptoms are persistent, a second dose may be needed.. Another good thing about pyrantel is that it is not well absorbed into the body from the intestines, so it produces very few side effects. At most, mild symptoms such as nausea, diarrhea, headache, and dizziness might be expected. In very rare cases, pyrantel has caused temporary worsening of myasthenia gravis (resulting in muscle weakness) due to the drug's effect on nerve receptors controlling muscular movements Even with an overdose of pyrantel, minimal toxicity is expected. In fact, there are no reports of serious human poisoning with pyrantel in the medical literature.

If you have questions about an adverse reaction or possible overdose of pyrantel, immediately check the webPOISONCONTROL^® online tool or call Poison Control at 1-800-222-1222 for help 24 hours a day, every day.

Leslie A. McCament-Mann, PhD, RPh
Clinical Toxicologist