# Anthelmintics

> Anthelmintics for MBBS Pharmacology — albendazole, ivermectin, praziquantel, DEC and niclosamide with worm-specific drugs of choice.

- Canonical URL: https://prepelephant.com/topics/mbbs/pharmacology/anthelmintics
- Exam / course: MBBS · Subject: Pharmacology
- Publisher: PrepElephant (https://prepelephant.com) — Prepared and reviewed by the PrepElephant Academic Review Team
- First published: 2026-10-02
- Last updated: 2026-10-02
- How to cite: "Anthelmintics", PrepElephant, https://prepelephant.com/topics/mbbs/pharmacology/anthelmintics

## Direct answer

Anthelmintics exploit biochemical targets that mammalian hosts lack. Albendazole and mebendazole bind nematode beta-tubulin and starve worms of glucose; ivermectin opens invertebrate glutamate-gated chloride channels causing flaccid paralysis; praziquantel floods schistosomes and tapeworms with calcium; diethylcarbamazine clears microfilariae. Matching the worm to the drug — ivermectin for strongyloidiasis and onchocerciasis, praziquantel for schistosomiasis, albendazole for hydatid disease and neurocysticercosis — is the essence of this topic.

## What you must remember

- Albendazole and mebendazole, benzimidazoles, block microtubule-mediated glucose uptake; a single four hundred milligram albendazole dose clears Ascaris, hookworm and pinworm, while albendazole's absorption (improved by fatty food) suits tissue disease — hydatid cyst months-long therapy and neurocysticercosis with corticosteroid cover.
- Benzimidazole toxicity is low — abdominal pain, transient transaminase rise — but they are avoided in the first trimester of pregnancy; albendazole is the preferred tissue-active agent.
- Ivermectin, an avermectin, is drug of choice for strongyloidiasis, onchocerciasis (microfilaricidal) and crusted scabies, and pairs with albendazole in lymphatic filariasis mass drug administration; killing microfilariae provokes the Mazzotti reaction of itching, fever and hypotension.
- Praziquantel raises tegumental calcium permeability, causing contraction and vacuolisation — drug of choice for all schistosomes, taeniasis, diphyllobothriasis and neurocysticercosis (with steroids); contraindicated in ocular cysticercosis where inflammatory destruction of the eye can blind.
- Diethylcarbamazine is the microfilaricidal drug for Wuchereria bancrofti and Brugia malayi, for Loa loa and tropical pulmonary eosinophilia; contraindicated in onchocerciasis where ivermectin is used, and capable of encephalopathy with heavy Loa loa microfilaraemia; DEC-fortified salt was a historic elimination strategy.
- Niclosamide, unabsorbed and safe, kills adult tapeworms in the lumen but not larval cysts; pyrantel pamoate single-dose therapy for pinworm and Ascaris agonises nematode nicotinic receptors; triclabendazole is the fascioliasis drug of choice.
- Avoid in pregnancy: albendazole, mebendazole, ivermectin and praziquantel where alternatives exist; pyrantel carries the best pregnancy profile among the narrow options.

## Common confusion

The filarial drugs are forever swapped: diethylcarbamazine treats lymphatic filariasis but is contraindicated in onchocerciasis, where ivermectin rules — reversing the pair harms the eye. Equally, praziquantel and albendazole compete for neurocysticercosis: albendazole is generally preferred for better tissue levels, but praziquantel wins for taeniasis and schistosomiasis where albendazole is useless.

## Exam-focused takeaway

Theory answers should group drugs by mechanism and then deliver the worm-to-drug map with doses where classical. Viva examiners ask why ocular cysticercosis excludes praziquantel and what the Mazzotti reaction signifies. MCQs test beta-tubulin binding, ivermectin's chloride channel, DEC contraindications, neurocysticercosis management and single-dose albendazole for soil-transmitted helminths.

## Frequently asked questions

### How do albendazole and mebendazole kill worms?

They bind nematode beta-tubulin selectively, disabling microtubule-dependent glucose uptake so the worm starves — host tubulin is far less susceptible.

### Which drug is chosen for strongyloidiasis and onchocerciasis?

Ivermectin — it opens glutamate-gated chloride channels found only in invertebrates, paralysing the parasite; diethylcarbamazine is avoided in onchocerciasis.

### Why is praziquantel contraindicated in ocular cysticercosis?

Dying intraocular cysts ignite inflammation that can destroy the eye, so lesion removal precedes any anthelmintic.

### What is the Mazzotti reaction?

An allergic response to dying microfilariae after ivermectin or DEC — itching, urticaria, fever, lymphadenitis and hypotension — managed with antihistamines and sometimes corticosteroids.

### Which anthelmintic treats hydatid disease?

Albendazole, given in prolonged courses peri-operatively or as standalone therapy for inoperable cysts, alongside meticulous surgical technique with scolicidal agents to prevent anaphylaxis from cyst spillage.