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What prescription gets rid of parasites?


ISSUE: FDA is concerned about the health of consumers who may self-medicate by taking ivermectin products intended for animals, thinking they can be a substitute for ivermectin intended for humans.

BACKGROUND: The FDA’s Center for Veterinary Medicine has recently become aware of increased public visibility of the antiparasitic drug ivermectin after the announcement of a research article that described the effect of ivermectin on SARS-CoV-2 in a laboratory setting. The Antiviral Research pre-publication paper, «The FDA-approved drug ivermectin inhibits the replication of SARS-CoV-2 in vitro» documents how SARS-CoV-2 (the virus that causes COVID-19) responded to ivermectin when exposed in a petri dish.

Ivermectin is FDA-approved for use in animals for prevention of heartworm disease in some small animal species, and for treatment of certain internal and external parasites in various animal species.


  • People should never take animal drugs, as the FDA has only evaluated their safety and effectiveness in the particular animal species for which they are labeled. These animal drugs can cause serious harm in people.
  • People should not take any form of ivermectin unless it has been prescribed by a licensed health care provider and is obtained through a legitimate source.
  • Ivermectin is an important part of a parasite control program for certain species and should only be given to animals for approved uses or as prescribed by a veterinarian in compliance with the requirements for extra-label drug use.
  • If you are having difficulty locating a particular ivermectin product for your animal(s), FDA recommends that you consult with your veterinarian.

Why is this medication prescribed?

Ivermectin is used to treat strongyloidiasis (threadworm; infection with a type of roundworm that enters the body through the skin, moves through the airways and lives in the intestines). Ivermectin is also used to control onchocerciasis (river blindness; infection with a type of roundworm that may cause rash, bumps under the skin, and vision problems including vision loss or blindness). Ivermectin is in a class of medications called anthelmintics. It treats strongyloidosis by killing the worms in the intestines. It treats onchocerciasis by killing the developing worms. Ivermectin does not kill the adult worms that cause onchocerciasis and therefore it will not cure this type of infection.

How should this medicine be used?

Ivermectin comes as a tablet to take by mouth. It is usually taken as a single dose on an empty stomach with water. If you are taking ivermectin to treat onchocerciasis, additional doses 3, 6, or 12 months later may be necessary to control your infection. Follow the directions on your prescription label carefully, and ask your doctor or pharmacist to explain any part you do not understand. Take ivermectin exactly as directed. Do not take more or less of it or take it more often than prescribed by your doctor.

If you are taking ivermectin to treat strongyloidiasis, you will need to have a stool exam at least three times during the first 3 months after your treatment to see if your infection has cleared. If your infection has not cleared, your doctor will probably prescribe additional doses of ivermectin.

Other uses for this medicine

Ivermectin is also sometimes used to treat certain other roundworm infections, head or pubic lice infestation, and scabies (itchy skin condition caused by infestation with small mites that live under the skin). Talk to your doctor about the risks of using this medication for your condition.

This medication may be prescribed for other uses; ask your doctor or pharmacist for more information.

What special precautions should I follow?

Before taking ivermectin,

  • tell your doctor and pharmacist if you are allergic to ivermectin, any other medications, or any of the ingredients in ivermectin tablets. Ask your pharmacist for a list of the ingredients.
  • tell your doctor and pharmacist what other prescription and nonprescription medications, vitamins, nutritional supplements, and herbal products you are taking or plan to take while you are taking ivermectin. Your doctor may need to change the doses of your medications or monitor you carefully for side effects.
  • tell your doctor if you have or have ever had conditions that affect your immune system, such as human immunodeficiency virus (HIV), or any other medical condition.
  • tell your doctor if you are pregnant, plan to become pregnant, or are breast-feeding. If you become pregnant during your treatment with ivermectin, call your doctor.
  • if you are taking ivermectin for onchocerciasis, you should know that you may experience dizziness, lightheadedness, and fainting when you get up too quickly from a lying position. To avoid this problem, get out of bed slowly, resting your feet on the floor for a few minutes before standing up.if you are taking ivermectin for strongyloidiasis and have had loiasis (Loa loa infection with a type of worm that causes skin and eye problems) or if you have ever lived in or traveled to areas of West or Central Africa where loiasis is common, you should know that you may have a serious reaction. Call your doctor immediately if you experience blurred vision, head or neck pain, seizures or difficulty walking or standing.

What special dietary instructions should I follow?

Unless your doctor tells you otherwise, continue your normal diet.

What should I do if I forget a dose?

Ivermectin is usually taken as a single dose. Tell your doctor if you do not take your medication.

What side effects can this medication cause?

Ivermectin may cause side effects. Tell your doctor if any of these symptoms are severe or do not go away:

  • dizziness
  • loss of appetite
  • nausea
  • vomiting
  • stomach pain or bloating
  • diarrhea
  • constipation
  • weakness
  • uncontrollable shaking of a part of the body
  • chest discomfort

If you are taking ivermectin to treat onchocerciasis, you may also experience the following side effects. Tell your doctor if any of these symptoms are severe or do not go away:

  • swelling of the eyes, face, arms, hands, feet, ankles, or lower legs
  • joint pain and swelling
  • painful and swollen glands of the neck, armpit or groin
  • rapid heartbeat
  • eye pain, redness, or tearing
  • swelling of the eye or eyelids
  • abnormal sensation in the eyes
  • fever

Some side effects can be serious. If you experience any of these symptoms, call your doctor immediately:

  • blistering or peeling skin
  • rash
  • hives
  • itching
  • sleepiness. confusion, disorientation, or coma (loss of consciousness for a period of time)

Ivermectin may cause other side effects. Call your doctor if you have any unusual problems while taking this medication.

What should I know about storage and disposal of this medication?

Keep this medication in the container it came in, tightly closed, and out of reach of children. Store it at room temperature and away from excess heat and moisture (not in the bathroom).

Unneeded medications should be disposed of in special ways to ensure that pets, children, and other people cannot consume them. However, you should not flush this medication down the toilet. Instead, the best way to dispose of your medication is through a medicine take-back program. Talk to your pharmacist or contact your local garbage/recycling department to learn about take-back programs in your community. See the FDA’s Safe Disposal of Medicines website ( for more information if you do not have access to a take-back program.

It is important to keep all medication out of sight and reach of children as many containers (such as weekly pill minders and those for eye drops, creams, patches, and inhalers) are not child-resistant and young children can open them easily. To protect young children from poisoning, always lock safety caps and immediately place the medication in a safe location – one that is up and away and out of their sight and reach.

In case of emergency/overdose

In case of overdose, call the poison control helpline at 1-800-222-1222. Information is also available online at If the victim has collapsed, had a seizure, has trouble breathing, or can’t be awakened, immediately call emergency services at 911.

Symptoms of overdose may include:

  • rash
  • hives
  • seizure
  • headache
  • tingling of hands or feet
  • weakness
  • loss of coordination
  • stomach pain
  • nausea
  • vomiting
  • diarrhea
  • dizziness
  • shortness of breath
  • swelling of the face, arms, hands, feet, ankles, or lower legs

What other information should I know?

Keep all appointments with your doctor and the laboratory. Your doctor may order certain lab tests to check your body’s response to ivermectin.

Do not let anyone else take your medication. Your prescription is probably not refillable.

It is important for you to keep a written list of all of the prescription and nonprescription (over-the-counter) medicines you are taking, as well as any products such as vitamins, minerals, or other dietary supplements. You should bring this list with you each time you visit a doctor or if you are admitted to a hospital. It is also important information to carry with you in case of emergencies.

Brand names

  • Stromectol ®

Last Revised — 07/15/2022
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AHFS ® Patient Medication Information™. © Copyright, 2023. The American Society of Health-System Pharmacists ® , 4500 East-West Highway, Suite 900, Bethesda, Maryland. All Rights Reserved. Duplication for commercial use must be authorized by ASHP.

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Pyrantel: A Safe and Effective Pinworm Treatment

pyrantel mother giving pinworm medicine to daughter

Pyrantel is an important drug for the control of intestinal worms in people and animals. It is estimated that close to 1 billion people are infested with intestinal worms globally. Pyrantel is a safe, effective, and inexpensive treatment for intestinal worms, and usually cures the condition after a single dose. It has very few side effects and is not known to cause severe toxicity in humans.

pyrantel helmiths under microscope

Need help? Get help online or
Call 1-800-222-1222

The Full Story

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 web POISON CONTROL ® 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


Call 1-800-222-1222 or

Prevention Tips

  • Clean up animal waste.
  • Wash hands before eating or preparing food.
  • Wash hands after contact with animals or feces.
  • If a person is diagnosed with intestinal worms, the entire household should be treated to prevent spread and reinfestation.
  • When using an OTC anthelmintic, follow all instructions. Contact a healthcare professional if one dose is ineffective or if more than minor side effects occur.
  • Keep all medications in child-resistant packaging and away from children and pets.

This Really Happened

Case 1. A 4-year-old Asian girl was treated with a non-prescription pinworm medication containing pyrantel pamoate. Two days later, she was seen at a clinic because of a drooping eyelid and periodic double vision. She was diagnosed with ocular myasthenia gravis (OMG), which responded to usual treatment for that condition. She did not receive pyrantel again, and the problem did not recur (from Shen et al., 2019).

Case 2. A 72-year-old man received a single dose of pyrantel pamoate (1000 mg) for roundworm infestation. Within a few hours, he noticed fatigue when walking and also when he chewed. Drooping eyelids, fatigue, limb weakness, and difficulty breathing followed. The symptoms improved gradually with several months of prednisone treatment. It was likely that pyrantel had aggravated an undiagnosed case of myasthenia gravis in this man (from Bescansa et al., 1991).

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