Cat Worm Medicine Side Effects

During your cat's annual exam, your veterinarian may tell you that your pet has contracted gastronintestinal worms and recommend medication. The type of anthelmintic (worm-killing) drug prescribed depends on the kind of worm diagnosed in the veterinary lab. Because a number of anthelmintics cause side effects in cats, consult with your doctor about possible ramifications for your pet prior to treatment.

  1. Fenbendazole

    • Veterinarians commonly prescribe fenbendazole (trade name Panacur or SafeGuard) to kill roundworms, hookworms, tapeworms, lungworms and/or flukes in your cat. The medication is also used successfully to treat Giardia protozoa parasites. Fenbendazole works by inhibiting the uptake of glucose by the parasite, effectively starving it to death. According to "Saunders Handbook of Veterinary Drugs" by Dr. Mark G. Papich, there are no known contraindications or drug interactions with fenbendazole, although some cats have experienced episodes of diarrhea and vomiting after administration.

    Praziquantel

    • Prescribed under the trade name Droncit, praziquantel eradicates your cat's tapeworms. Tapeworms are transmitted in the bodies of fleas and establish themselves in your cat's intestinal tract, showing as small, rice-like segments in the feces and around the cat's anus. Praziquantel paralyzes the neural systems of the worms, causing them to die. While there are no contraindications or known drug interactions with this medication, some cats suffer anorexia, intense vomiting and transient (on and off) diarrhea.

    Ivermectin

    • Animal practitioners use the anti-parasitic ivermectin to treat heartworms, lungworms and Demodex mites in cats. Also called Heartguard, ivermectin in lower doses destroys the parasites by inhibiting their neuro-transmitters and killing brain activity. Side effects of toxicity include depression, ataxia (stumbling walk), vision difficulties, and in the worst cases, coma and death. Ivermectin is not recommended for kittens under six weeks of age or adult cats with a high level of heartworm infestation. Your veterinarian will need to test your cat for heartworms prior to prescribing this medication.

    Dichlorvos

    • The main ingredient in many over-the-counter dewormers, dichlorvos is used primarily to treat hookworms, roundworms and whip worms. This medication demolishes the parasite's central nervous system, killing it and allowing it to pass from your cat's body. An organophosphate, dichlorvos is chemically compounded from phosphorus and a phosphoric acid and is poisonous if administered in large doses. Signs of toxicity include diarrhea, excess salivation, difficulty breathing and muscle twitching. In his book "Pharmacology for Veterinary Technicians," Dr. Robert L. Bill says drugs such as dichlorvos "should not be used in animals with heartworm infection. Use of these drugs in animals with heartworm can produce severe reactions, including dypsnea (difficulty breathing), collapse, and sudden death."