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Pharmacokinetics and metabolism of avermectins in livestock.
Abstract: The kinetics of avermectin disposition and metabolism in ruminant livestock and horses are reviewed with particular emphasis on the influence of route of administration and formulation on persistence of residues in tissues and excretion in faeces. Because information is not publicly available on other compounds in this class currently under development (e.g. moxidectin, doramectin), ivermectin only is considered. The biological half-life of ivermectin in plasma is similar in cattle and sheep but because of a larger volume of distribution, plasma clearance is more rapid in sheep. However, injection of the subcutaneous formulation of ivermectin prolongs plasma residence time and persistence of drug residues particularly in liver and fat. Increasing the organic solvent content of subcutaneous formulations slows the release of drug from the injection site and thereby prolongs its presence in the bloodstream. Because ivermectin and its metabolites are mainly excreted in bile, residues continue to appear in faeces for substantially longer following subcutaneous injection than after oral dosing. Aqueous based injectable formulations in cattle may therefore reduce the impact of ivermectin treatment on dung fauna. Binding of avermectins to digesta particulates during gut transit may potentially lower drug bioavailability and also contribute to faecal residues. Further research on formulation and dosage strategies is advocated to increase bioavailability at the gastrointestinal site of action so that both dose rate and faecal residues can be reduced.
Publication Date: 1993-06-01 PubMed ID: 8346648DOI: 10.1016/0304-4017(93)90143-bGoogle Scholar: Lookup The Equine Research Bank provides access to a large database of publicly available scientific literature. Inclusion in the Research Bank does not imply endorsement of study methods or findings by Mad Barn.
- Journal Article
- Review
Summary
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This research article reviews the pharmacokinetics and metabolism of a drug known as avermectin in livestock and horses, focusing on how its administration method and formulation affect how long it stays in animal tissues and its excretion in faeces.
General Overview of the Research
- The study focuses on the pharmacokinetics, or the movement of drugs within the body, and the metabolism of avermectins in livestock. In particular, the research reviews how the persistence of avermectin residues in tissues and their excretion in faeces are influenced by how these drugs are administered and combined with other substances.
- Among the avermectin class of drugs, only ivermectin is discussed in this article due to the lack of publicly available information on other drugs in this class that are currently under development such as moxidectin and doramectin.
Understanding of Ivermectin in Animals
- Despite the biological half-life of ivermectin being similar in cattle and sheep, plasma clearance (the rate at which a drug is removed from the body) occurs more rapidly in sheep due to a larger volume of distribution.
- Subcutaneous injection (under the skin) of ivermectin prolongs its stay in the bloodstream and increases the persistence of drug residues in the liver and fat tissues of animals. The organic solvent content in subcutaneous formulations also affects the release of the drug from the injection site and its presence in the bloodstream.
Excretion of Ivermectin and its Implications
- Most of ivermectin and its metabolites are excreted through bile, leading to its prolonged appearance in faeces following subcutaneous injections compared to oral administration.
- This can have ecological impacts, as the persistence of ivermectin in faeces can affect dung fauna. In this context, aqueous based injectable formulations could potentially lessen the environmental impact of ivermectin treatment.
Need for Further Research
- The researchers suggest that the binding of avermectins to digesta particulates during gut transit could potentially lower drug bioavailability (the extent to which a drug becomes available in the body) and also contribute to drug residues in the faeces.
- Additional research is recommended on formulation and dosage approaches to increase ivermectin’s bioavailability at the gastrointestinal site of action. The goal is to reduce both the dose rate and the presence of drug residues in faeces for ecological considerations.
Cite This Article
APA
Steel JW.
(1993).
Pharmacokinetics and metabolism of avermectins in livestock.
Vet Parasitol, 48(1-4), 45-57.
https://doi.org/10.1016/0304-4017(93)90143-b Publication
Researcher Affiliations
- CSIRO Division of Animal Health, McMaster Laboratory, Glebe, N.S.W., Australia.
MeSH Terms
- Animals
- Animals, Domestic / metabolism
- Cattle / metabolism
- Drug Residues
- Horses / metabolism
- Ivermectin / pharmacokinetics
- Ruminants / metabolism
- Sheep / metabolism
Citations
This article has been cited 14 times.- Wald ME, Claus C, Konrath A, Nieper H, Muluneh A, Schmidt V, Vahlenkamp TW, Sieg M. Ivermectin Inhibits the Replication of Usutu Virus In Vitro. Viruses 2022 Jul 27;14(8).
- Laing R, Doyle SR, McIntyre J, Maitland K, Morrison A, Bartley DJ, Kaplan R, Chaudhry U, Sargison N, Tait A, Cotton JA, Britton C, Devaney E. Transcriptomic analyses implicate neuronal plasticity and chloride homeostasis in ivermectin resistance and response to treatment in a parasitic nematode. PLoS Pathog 2022 Jun;18(6):e1010545.
- Moroni B, Granados Torres JE, López-Olvera JR, Espinosa Cerrato J, Ráez Bravo A, Mentaberre G, Fandos P, Pazzi M, Romagnoli M, Gardini G, Rossi L, Valldeperes M, Serrano E, Ramos B, Odore R. Ivermectin Plasma Concentration in Iberian Ibex (Capra pyrenaica) Following Oral Administration: A Pilot Study. Front Vet Sci 2022;9:830157.
- Imperiale F, Lanusse C. The Pattern of Blood-Milk Exchange for Antiparasitic Drugs in Dairy Ruminants. Animals (Basel) 2021 Sep 22;11(10).
- Meredith HR, Furuya-Kanamori L, Yakob L. Optimising systemic insecticide use to improve malaria control. BMJ Glob Health 2019;4(6):e001776.
- Konecny P, Weatherall CJ, Adhikari S, Duflou J, Marjoniemi V, Pretorius CJ, McWhinney B. Case Report: Subcutaneous Ivermectin Pharmacokinetics in Disseminated Strongyloides Infection: Plasma and Postmortem Analysis. Am J Trop Med Hyg 2018 Dec;99(6):1580-1582.
- Chen LP, Wang P, Sun YJ, Wu YJ. Direct interaction of avermectin with epidermal growth factor receptor mediates the penetration resistance in Drosophila larvae. Open Biol 2016 Apr;6(4):150231.
- Jacobs CT, Scholtz CH. A review on the effect of macrocyclic lactones on dung-dwelling insects: Toxicity of macrocyclic lactones to dung beetles. Onderstepoort J Vet Res 2015 Apr 16;82(1):858.
- Cala AC, Ferreira JF, Chagas AC, Gonzalez JM, Rodrigues RA, Foglio MA, Oliveira MC, Sousa IM, Magalhães PM, Barioni Júnior W. Anthelmintic activity of Artemisia annua L. extracts in vitro and the effect of an aqueous extract and artemisinin in sheep naturally infected with gastrointestinal nematodes. Parasitol Res 2014 Jun;113(6):2345-53.
- González Canga A, Sahagún Prieto AM, Diez Liébana MJ, Fernández Martínez N, Sierra Vega M, García Vieitez JJ. The pharmacokinetics and interactions of ivermectin in humans--a mini-review. AAPS J 2008;10(1):42-6.
- Craigmill AL, Cortright KA. Interspecies considerations in the evaluation of human food safety for veterinary drugs. AAPS PharmSci 2002;4(4):E34.
- Alquarawi AA, Ali BH. A survey of the literature (1995-1999) on the kinetics of drugs in camels (Camelus dromedarius). Vet Res Commun 2000 May;24(4):245-60.
- Kim S, Sayem SAJ, Chae H, Park SW, Gui L, Park SC, Kang J. Comparative pharmacokinetic and bioequivalence of nine oral ivermectin formulations in dogs. J Vet Sci 2025 Nov;26(6):e88.
- Eriksson M, Nylén S. Case report: C57BL/6NTac and C57BL/6NCrl mice displaying neurological signs after deworming with ivermectin. Lab Anim 2025 Jun;59(3):374-383.
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