Antiparasitic Drugs

Antiparasitic medications are drugs that treat parasitic infections. These infections result from parasites, which are tiny organisms that live on or inside of people and animals. There are many types of antiparasitic drugs. Each drug targets a specific parasite. The infections they treat cause symptoms that range from mild to severe.

What are antiparasitic drugs?

These medications work by killing parasites, stopping their growth or paralyzing them. A parasite is a tiny microorganism (microscopic organism). It can live inside your body or on the skin or hair of humans and other animals. Parasites get their nutrients from these people or animals (the “host”).

Different types of antiparasitic drugs target specific parasites. Some of these drugs have serious side effects. Your provider will recommend the right drug and dose for you based on the parasite that caused the infection.


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What do antiparasitic drugs treat?

Antiparasitic drugs treat many kinds of infections that result from thousands of types of parasites. Three main types of parasites can make people sick. They are:

  • Ectoparasites: Head lice and pubic lice, fleas, ticks and bedbugs are common types of ectoparasites. They live outside the host’s body, often on their skin or hair. Some ectoparasites (such as bedbugs) live on sheets or furniture. They crawl to the host, bite their skin and suck their blood for nourishment.
  • Helminths: Hookworms, roundworms and pinworms are types of helminths. They commonly live inside your body. These worms have multiple cells and organs.
  • Protozoas: These organisms have only one cell. An amoeba is a type of protozoa. These single-cell organisms are very small and multiply inside your body.

Parasites cause billions of infections all over the world. There are many types of parasitic infections. One of the most common parasitic infections is malaria. Sometimes, parasites can cause gastroenteritis (stomach flu). In the United States, some of the most common parasitic infections are:

How do antiparasitic drugs work?

There are many different types of parasites, infections and antiparasitic drugs. Each antiparasitic medication works on a specific parasite. Healthcare providers match the type of medication to the particular parasite that’s causing the infection. Antiparasitic drugs work by:

  • Killing the parasite or the parasite’s eggs.
  • Stopping the parasite’s growth.
  • Paralyzing the parasites so they cannot attach themselves to the host.

Depending on the type of infection and the parasite that caused it, you may take antiparasitic medications:

  • Orally (by mouth).
  • Intravenously (through a needle).
  • Topically (by applying medicine to your skin or hair).

Who should use antiparasitic drugs?

In general, children and adults who have an infection that results from a parasite need antiparasitic medication. But the side effects of each drug vary, and some side effects are severe. Your provider will consider the risks and benefits of antiparasitic medications and recommend the most appropriate treatment for you.

What are the types of antiparasitic drugs?

There are dozens of kinds of antiparasitic drugs. Healthcare providers group the main types of these drugs into three categories. They each treat the three main types of infection. The main types of antiparasitic drugs are:

  • Antiprotozoal agents, which treat protozoas. These include antimalarial drugs.
  • Antihelminthic agents, which treat infections that result from parasitic worms.
  • Ectoparasiticides, which providers use to kill lice, scabies and other ectoparasites.

How effective are antiparasitic drugs?

The effectiveness varies depending on the medication. Most antiparasitic drugs are effective. But there isn’t one drug that targets all parasites. For some parasitic infections, there is no treatment.

What are the risks and side effects of using antiparasitic drugs?

Side effects from antiparasitic drugs vary widely. Some drugs have mild side effects. Others can cause severe kidney damage, behavioral changes and problems with your nervous system. The most common side effects are:

This isn’t a complete list of possible side effects. Some types of antiparasitic medications can have serious side effects. These include abnormal heart rate, vision changes, hallucinations and psychosis. It’s essential to follow your provider’s directions carefully and report any side effects right away.

Can you overdose on antiparasitic drugs?

Some antiparasitic medications can cause serious health problems if you take more than you should or you take them for too long. These problems include:

How long should you take antiparasitic drugs?

The dosing instructions vary with each type of drug. Your provider will tell you how much to take and how long to take it. Follow your provider’s dosing instructions carefully. You may need to take another dose of the medication about a week to 10 days after you finish the first dose.

Who should not take antiparasitic drugs?

Share your health history with your provider before taking antiparasitic medications. Some people shouldn’t take these drugs, including people with kidney disease. If you have a weakened immune system, tell your provider.

If you’re pregnant or breastfeeding, talk to your provider before you take these medications. Some of them can harm your baby.

A note from Cleveland Clinic

Many types of antiparasitics treat a wide range of parasitic infections. Before taking these medications, tell your provider about your health history. Be sure to mention if you’re pregnant or breastfeeding. Some of these medications have serious side effects. Your provider will discuss these side effects with you. Follow your provider’s instructions carefully when taking these medications.

Medically Reviewed

Last reviewed by a Cleveland Clinic medical professional on 05/06/2022.

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