Anthelmintics Overview and Mechanisms
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Questions and Answers

What are anthelmintics?

  • Drugs used to kill &/or expel parasitic worms from the body (correct)
  • Agents used for expelling parasites from the intestinal tract
  • Agents that can kill intestinal parasites and expel them out
  • All of the above

    • What are vermifuges used for?

    Expelling parasites from the intestinal tract

    What are vermicides?

    Agents which can kill intestinal parasites and expel them out

    List the properties of an ideal anthelmintic.

    <p>Broad spectrum of activity against mature and immature parasites, easier to administer, wide margin of safety, minimum withholding period, economical, selectively toxic to helminth parasites.</p> Signup and view all the answers

    The selectivity of action of anthelmintics in helminth parasites depends on what factors?

    <p>Drug receptor unique to the parasite, inhibiting vital metabolic processes, pharmacokinetic properties causing higher concentrations in the parasite.</p> Signup and view all the answers

    Except for ____, the other commonly used anthelmintics do not normally produce pharmacological effects.

    <p>organophosphorus compounds</p> Signup and view all the answers

    Most anthelmintics may be used in all domestic animal species.

    <p>True</p> Signup and view all the answers

    In which species cannot levamisole be used?

    <p>Horses and cats</p> Signup and view all the answers

    Praziquantel can only be used in which species?

    <p>Dogs, cats, and horses</p> Signup and view all the answers

    Piperazine salts can only be used in which species?

    <p>Monogastrics</p> Signup and view all the answers

    Salicylanilides can only be used in which species?

    <p>Ruminant species</p> Signup and view all the answers

    Nitroxynil can only be used in which species?

    <p>Ruminant species</p> Signup and view all the answers

    Clorsulon can only be used in which species?

    <p>Ruminant species</p> Signup and view all the answers

    What drugs are in the Benzimidazoles (carbamates) class?

    <p>Albendazole, fenbendazole, mebendazole, oxfendazole, oxibendazole, parbendazole</p> Signup and view all the answers

    What drugs are in the Benzimidazoles (thiazoles) class?

    <p>Thiabendazole, cambendazole</p> Signup and view all the answers

    What drugs are in the Probenzimidazoles?

    <p>Netobimin, Febantel</p> Signup and view all the answers

    What drugs are in the Imidazothiazoles?

    <p>Levamisole, tetramisole</p> Signup and view all the answers

    What drugs are in the Tetrahydropyrimidines class?

    <p>Pyrantel, morantel, oxantel</p> Signup and view all the answers

    What drugs are in the Organophosphate compounds class?

    <p>Dichlorvos, trichlorfon, haloxon, coumaphos, crufomate</p> Signup and view all the answers

    What drugs are in the Macrocyclic lactones (avermectins) class?

    <p>Ivermectin, abamectin, doramectin, eprinomectin, selamectin</p> Signup and view all the answers

    What drugs are in the Macrocyclic lactones (Milbemycin) class?

    <p>Milbemycin oxime, moxidectin</p> Signup and view all the answers

    What drugs are in the Piperazine compounds class?

    <p>Piperazine, Diethylcarbamazine citrate (DEC)</p> Signup and view all the answers

    What drugs are in the Benzenedisulphonamide class?

    <p>Clorsulon</p> Signup and view all the answers

    What drugs are in the Isoquinoline class?

    <p>Praziquantel, epsiprantel</p> Signup and view all the answers

    What drugs are in the Salicylanilide class?

    <p>Closantel, oxyclozanide, rafoxanide</p> Signup and view all the answers

    What drugs are in the Nitrobenzonitrile class?

    <p>Nitroxynil</p> Signup and view all the answers

    What drugs are in the Arsenical compound class?

    <p>Thiacetarsamide sodium, melarsomine</p> Signup and view all the answers

    Benzimidazoles are typically mostly effective against _______________, but substituted BZDs (carbamate or thiazole ones) are effective against certain _____________?

    <p>nematodes, tapeworms and flukes</p> Signup and view all the answers

    Describe the spectrum, safety margin, MOA, pharmacokinetics, and metabolism of benzimidazoles.

    <p>Broad spectrum (GI &amp; lung nematodes) with a wide safety margin, selective - irreversible binding to nematode tubulin → prevents formation of microtubules; resistance due to variation in B-tubulin, low aqueous solubility; hence absorption from GIT is poor.</p> Signup and view all the answers

    Study Notes

    Anthelmintics Overview

    • Anthelmintics are drugs designed to kill and expel parasitic worms from the body.
    • Vermifuges are agents that specifically expel parasites from the intestinal tract.
    • Vermicides not only expel but also kill intestinal parasites.

    Ideal Anthelmintic Properties

    • Should have a broad spectrum of activity against both mature and immature parasites.
    • Easy to administer with a wide margin of safety.
    • Should have minimal withholding periods and be economical.
    • Must be selectively toxic to helminth parasites.

    Mechanism of Selectivity

    • The action of anthelmintics relies on drug receptors being unique or more sensitive in parasites.
    • They work by inhibiting essential metabolic processes in the parasite that are either unimportant or absent in the host.
    • Pharmacokinetic properties ensure higher concentrations in parasites than in host cells.

    Exceptions in Anthelmintics Usage

    • Organophosphorus compounds and levamisole are exceptions, having pharmacological effects through specific mechanisms.
    • Most anthelmintics can be used across various domestic animal species, with exceptions for specific drugs like levamisole and praziquantel.

    Species Specificity of Anthelmintics

    • Levamisole is not suitable for horses and cats.
    • Praziquantel is only approved for use in dogs, cats, and horses.
    • Piperazine salts are restricted to monogastrics.
    • Salicylanilides, nitroxynil, and clorsulon are only for ruminant species.

    Classes of Anthelmintics

    • Benzimidazoles (carbamates) include Albendazole, Fenbendazole, Mebendazole, Oxfendazole, Oxibendazole, Parbendazole.
    • Benzimidazoles (thiazoles) consist of Thiabendazole and Cambendazole.
    • Probenzimidazoles are inactive until converted to active forms by ruminal microbes or the liver, including Netobimin and Febantel.
    • Imidazothiazoles consist of Levamisole and Tetramisole.
    • Tetrahydropyrimidines include Pyrantel, Morantel, and Oxantel.
    • Organophosphate compounds include Dichlorvos, Trichlorfon, Haloxon, Coumaphos, and Crufomate.
    • Macrocyclic lactones (avermectins) include Ivermectin, Abamectin, Doramectin, Eprinomectin, and Selamectin.
    • Macrocyclic lactones (Milbemycin) consist of Milbemycin oxime and Moxidectin.
    • Piperazine compounds include Piperazine and Diethylcarbamazine citrate (DEC).
    • Benzenedisulphonamide refers to Clorsulon.
    • Isoquinoline class has Praziquantel and Epsiprantel.
    • Salicylanilide class includes Closantel, Oxyclozanide, and Rafoxanide.
    • Nitrobenzonitrile class is represented by Nitroxynil.
    • Arsenical compounds consist of Thiacetarsamide sodium and Melarsomine.

    Benzimidazoles Efficacy

    • Generally effective against nematodes; specific substituted benzimidazoles target certain tapeworms and flukes.
    • Exhibit broad-spectrum efficacy against gastrointestinal and lung nematodes with a wide safety margin.
    • Mechanism of action involves irreversible binding to β-tubulin in nematodes, preventing microtubule formation.
    • Resistance development in parasites is often due to variations in β-tubulin.

    Pharmacokinetics of Benzimidazoles

    • Lower aqueous solubility leads to poor gastrointestinal absorption.
    • Clinical application demands consideration of pharmacokinetics for effective treatment outcomes.

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    Description

    This quiz covers the essential properties and mechanisms of action of anthelmintics, drugs used to combat parasitic worms. It includes details on vermifuges, vermicides, and the selectivity of these agents based on their interaction with parasites. Test your knowledge on the unique characteristics that make an effective anthelmintic and its exceptions in usage.

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