Anthelmintic drugs

Anthelmintic drugs are medicinal substances used for the treatment and prevention of helminthiasis in animals. The mechanism of action of anthelmintic drugs differs due to morphological, physiological, biological and other features between individual classes and groups of helminths. They may have different sensitivity to the same anthelmintic drugs. Due to their chemical nature and differences in pharmacodynamics, the drugs act differently on the same groups of helminths.

  1. Piperazine (piperazine sulfate, piperazine phosphate, diethyl carbomazin). These drugs cause paralysis of the neuromuscular system of helminths, have an anticholinergic effect, thereby disrupting the transmission of impulses. Piperazine salts are widely used against ascarids, filariae, and pulmonary nematodes;
  2. Imidazolethiazoles (tetramizole, levamisole, pyrantel). The action of these drugs is based on the depolarization of neuromuscular blocking agents, both in nematodes and their hosts. They are used against many nematodes, especially parasitic in the gastrointestinal tract;
  3. Benzimidazoles (thiabendazole, mebendazole, parbendazole, oxibendazole, etc.). Drugs in this group usually act on the intestinal cells of helminths, preventing glucose absorption, thereby causing helminth starvation. They are practically harmless to animals. However, helminths develop resistance to them with repeated use. The drugs can be used in groups. They are widely used against nematodes in sheep and horses, less often against cestodes and trematodes;
  4. Avermectins. Of this group, only ivermectin has widespread use against nematodes. The drug enhances the release and binding of gamma-aminobutyric acid in the nerve synapses of helminths. The drug acts as a neurotransmitter, transmitting signals between neurons. Ivermectin disrupts these signals, leading to paralysis of the nematodes;
  5. Organophosphates. Some organophosphorus compounds (dichlorvos, haloxon, trichlorfon) are active against nematodes. They inhibit cholinesterase, which leads to the accumulation of acetylcholine, paralysis of nematodes and their removal from the intestines. This group of drugs is used mainly for horses. The drugs have an additional insecticidal effect, they are used against the larvae of gastrointestinal gadflies;
  6. Salicylanilides (nitrosocanate, closantel, nitroxinil, rafoxanide, oxyclozanide, and others). The drugs prevent the production of ATP by the parasite by disrupting oxidative phosphorylation. They are most often used for fascioliasis, and niclosamide against pulmonary helminths.

Anthelmintic drugs are most often administered orally in the form of: tablets, dragees, powders with food, drink, in capsules at the root of the tongue and using a probe. For some helminthiasis, the drug is administered rectally. For muscular, pulmonary, hepatic, renal, abdominal and other helminthiasis, anthelmintic drugs are administered parenterally: subcutaneously, intramuscularly, intratracheally, externally.

Anthelmintic drugs are used individually (especially highly toxic to the body of animals and birds) or by group method. The frequency of use may vary. For intestinal helminthiasis, one or two applications are usually sufficient, for other helminthiasis, longer treatment is required. The dose of the drug can be used once or in small doses, if this increases the effectiveness.

Some helminths develop resistance to anthelmintic drugs. This phenomenon is observed when using drugs containing the benzimidazole group. Therefore, it is recommended to alternate the use of drugs belonging to different chemical groups, taking into account the variability of helminth generations.

Caution should be exercised when using anthelmintic drugs, especially when using highly toxic drugs, as poisoning may occur.

When poisoning animals with organophosphorus drugs, atropine is used intramuscularly at a dose of 0.5 mg/kg (5 ml of 1% solution per 100 kg) - cattle, horses, pigs.

In severe poisoning with relapses, atropine is administered repeatedly at intervals of 6-12 hours. To increase the effectiveness of treatment, 10% calcium chloride solution should be additionally administered intravenously at a dose of 0.5 ml/kg 1-2 times a day for 2-3 days, 4% glucose solution at a dose of 1 ml/kg and other drugs (vitamins, cardiac drugs) depending on the indications).

To avoid poisoning, precautions are of great importance:

  • Preliminary testing of the drug on a small group of farm animals;
  • Full feeding;
  • Compliance with instructions for the use of anthelmintic drugs;
  • Accurate dosage;
  • Strict adherence to feeding and watering regimens.
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