Therapeutics: parasiticide

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Endoparasiticides - Nematodes

Drugs for Nematodes

  • Disrupt parasite energy metabolism by binding to tubulin (required for uptake of nutrients).
  • Doses may need to be repeated in kittens or when treating specific infections.
  • Effective against larval and adult roundworms, some also ovicidal.
  • Products containing benzimidazoles or probenzimidazoles are labeled 1-BZ.
  • Fenbendazole    : lungworm ( Aleurostrongylus  [Aelurostrongylus abstrusus]  ). GI nematodes - Toxocara cati , Toxascaris leonina    , Ancylostoma    and Taenia spp    (tapeworm) not effective against Dipylidium    .
  • Mebendazole    : gastrointestinal nematodes, Echinococcus and Taenia    . Need to treat longer if treating tapeworms.
  • Praziquantel    : preferred treatment for Echinococcus .
  • Febantel    .


  • Nicotinic receptor agonists interfere with parasite nerve transmission   →   muscular paralysis and expulsion.
  • Restores depressed T-cell function.
    Low therapeutic index - toxic signs include salivation and muscle tremors.
  • Levamisole hydrochloride *    : lungworms ( Aleurostrongylus abstrusus , Capillaria aerophilia    ), immune stimulation, heartworm treatment (seek specialist advice). Unlicensed in cat.

Organophosphorous compounds

  • Dichlorvos    : roundworms, hookworms. Safer compounds are available.


  • Interfere with parasite nerve transmission   →   neuromuscular paralysis.
  • Effective against adults and larval gastrointestinal roundworms.
  • Pyrantel embonate    .


  • Piperazine    : modifies neurotransmission   →   relaxation and expulsion; for some roundworms, ie Toxocara    , Toxascaris    and Uncinaria ; little activity against larval Toxocara in kittens; ineffective against lungworms or tapeworms. Toxic in cats with overdose (muscle fasciculations, ataxia, salivation).
  • Diethylcarbamazine : piperazine derivative that acts in nicotine-like manner causing paralysis. Used for heartworm prophylaxis in dogs and has ascaricide activity. Has been used to treat Spirocerea lupi at very high doses.
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