Antiparasitics

Key takeaways

• Antiparasitics cover three jobs: killing intestinal worms (albendazole, mebendazole, levamisole, praziquantel), treating or preventing malaria (chloroquine, hydroxychloroquine), and treating skin parasites like scabies and lice (permethrin, crotamiton).
• Ivermectin and ornidazole treat protozoal and other worm or mite infections and don't fit neatly into either group.
• The practical difference between them is the specific parasite and, for antimalarials, where the exposure happened, since resistance varies by region.
• The #1 safety rule: chloroquine resistance is now widespread in most malaria-endemic regions, and hydroxychloroquine used long-term needs regular eye exams to catch retinal toxicity.

How antiparasitic medications work

Antiparasitic drugs disrupt something specific to the target organism's biology. Anthelmintics block glucose uptake or paralyze worm muscles so the worm can no longer stay attached to your gut. Antimalarials block the parasite's ability to process the byproduct of digesting blood inside your red blood cells. Topical agents disable the nervous system of mites and lice on contact. The right drug depends on the organism and where you picked it up.

Choosing between ivermectin, chloroquine, hydroxychloroquine, praziquantel, albendazole, mebendazole and permethrin

• Ivermectin treats scabies, strongyloides and several other worm infections, given as a short oral course or a repeated dose depending on the parasite.
• Chloroquine treats and prevents malaria, but resistance is now widespread across most malaria-endemic regions. It is no longer reliable everywhere, so a destination-specific choice matters.
• Hydroxychloroquine works similarly to chloroquine for malaria. With long-term or high-dose use it can damage the retina, so anyone on it for months or years needs regular eye exams.
• Praziquantel treats infections from flukes, including schistosomiasis, and from tapeworms, damaging the parasite's outer surface so your immune system can clear it.
• Albendazole treats a broad range of intestinal worm infections and some tissue-dwelling larval infections, dosed for days or longer depending on the worm.
• Mebendazole treats common intestinal worms like pinworm and roundworm, usually as a short course, by starving the worm of the glucose it needs to survive.
• Permethrin is a topical cream or lotion for scabies and lice. It kills mites and eggs on contact and typically needs one application, sometimes repeated after a week.

Ornidazole treats protozoal infections such as amoebiasis and giardiasis. Levamisole treats worm infections by paralyzing worm muscles. Crotamiton is a topical alternative to permethrin for scabies, though less consistently effective.

Common questions

Can I treat a parasite without knowing exactly which one I have?

No. Antiparasitics target a specific organism, and using the wrong one wastes time while the infection continues. A stool, blood or physical exam usually confirms which parasite you have first.

Are topical and oral antiparasitics interchangeable?

No. Topical creams like permethrin and crotamiton only reach parasites on your skin, such as mites and lice. Worms and protozoa inside your body need an oral drug that acts within the gut or is absorbed into your bloodstream.

Why does my antimalarial choice depend on where I'm traveling?

Malaria parasites have developed resistance to chloroquine across most regions where the disease is common. Prevention and treatment now depend on local resistance patterns, so always check current guidance for your destination rather than assuming an older drug still works.

Safety essentials

• Confirm chloroquine resistance status for your specific destination before relying on it for malaria prevention. In most regions today it is not fully protective.
• If you take hydroxychloroquine long-term, schedule regular eye examinations to catch retinal changes early. Any vision changes on this drug need prompt assessment.
• Complete the full course of any anthelmintic even if symptoms improve early; an incomplete course can leave parasites behind.
• Seek urgent care for severe abdominal pain, high fever, breathing difficulty or an allergic reaction after starting any antiparasitic.

This page is educational and does not replace advice from a doctor or pharmacist who knows your health history.