Examples of drugs used as anthelmintics include:
- Albendazole - Effective against: threadworms, roundworms, whipworms, tapeworms, hookworms
- Diethylcarbamazine - Effective against: Wuchereria bancrofti, Brugia malayi, Brugia timori, tropical pulmonary eosinophilia, loiasis
- Mebendazole - Effective against: pinworms, roundworms and hookworms
- Niclosamide - Effective against: tapeworms
- Ivermectin - Effective against: most common intestinal worms (except tapeworms)
- Thiabendazole - Effective against: roundworms, hookworms
- Pyrantel pamoate - Effective against: for most nematode infections
- Praziquantel - Effective against: nematodes, some trematodes
- Triclabendazole - Effective against: liver flukes
- Octadepsipeptides - Eg: Emodepside. Effective against a variety of gastrointestinal helminths
Many members of the piperazine family are successful anthelmintics.
Natural anthelmintics include black walnut, wormwood (Artemisia absynthium), clove (Syzygium aromaticum), tansy tea (Tanacetum vulgare), Hagenia (Hagenia abyssinica), kalonji (Nigella sativa) seeds, and the male fern (Dryopteris filix-mas). In Brazilian folk medicine, Plumeria P. acutifolia or P. rubra is also an anthelmintic.  Please note that many natural vermifuges or anthelmintics are poisonous and, in improper dosages, dangerous to humans as well as parasites.
The ability of worms to survive treatments that are generally effective at the recommended dose rate.
It is considered a major threat to the current future control of worm parasites of small ruminants and horses.
Development of Resistance
Treatment eliminates worms whose genotype renders them susceptible -Worms that are resistant survive and pass on their "resistance" genes
Resistant worms accumulate and finally treatment failure occurs -Clinical definition= <95% reduction in Fecal Egg Count
What causes Resistance?
- Treatment at frequent intervals
- >3 treatments per year
- Many farms >6 Tx per year
- Treating all animals at same time
- no refugia
- Treating and moving to clean pasture
- no dilution
- Under dosing
- worms with low-level resistance survive