Characterization of the antinociceptive and sedative effect of amitraz in horses.
Abstract: Amitraz, an acaricide used to control ectoparasites in animals has a complex pharmacological activity, including alpha2-adrenergic agonist action. The purpose of this research was to investigate the possible antinociceptive and/or sedative effect of amitraz in horses. The sedative effect of the intravenous (i.v.) injection of dimethylformamide (DMF, 5 mL, control) or amitraz (0.05, 0.10, 0.15 mg/kg), was investigated on the head ptosis test. The participation of alpha2-adrenergic receptors in the sedative effect provoked by amitraz was studied by dosing yohimbine (0.12 mg/kg, i.v.). To measure the antinociception, xylazine hydrochloride (1 mg/kg, i.v., positive control) and the same doses of amitraz and DMF were used. A focused radiant light/heat directed onto the fetlock and withers of a horse were used as a noxious stimulus to measure the hoof withdrawal reflex latency (HWRL) and the skin twitch reflex latency (STRL). The three doses of amitraz used (0.05, 0.10 and 0.15 mg/kg) provoked a dose-dependent relaxation of the cervical muscles. The experiments with amitraz and xylazine on the HWRL showed that after i.v. administration of all doses of amitraz there was a significant increase of HWRL up to 150 min after the injections. Additionally, there was a significant difference between control (DMF) and positive control (xylazine) values up to 30 min after drug injection. On the other hand, the experiments on the STRL show that after administration of amitraz at the dose of 0.15 mg/kg, a significant increase in STRL was observed when compared with the control group. This effect lasted up to 120 min after injection. However, no significant antinociceptive effect was observed with the 0.05 and 0.10 mg/kg doses of amitraz or at the 1.0 mg/kg dose of xylazine.
Publication Date: 1998-11-12 PubMed ID: 9811442DOI: 10.1046/j.1365-2885.1998.00150.xGoogle Scholar: Lookup
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- Journal Article
- Research Support
- Non-U.S. Gov't
Summary
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The study explores the potential pain relieving (antinociceptive) and sedative effects of Amitraz, a parasite control substance, in horses. The research discovered dose-dependent muscle relaxation and increased withdrawal reflex latency after administering Amitraz, indicating potential antinociceptive and sedative effects.
Research Methodology
- The study investigated the sedative effect of Amitraz by assessing the degree of head drooping (referred to as the head ptosis test) in horses post the administration of various doses of Amitraz (0.05, 0.10, and 0.15 mg/kg) intravenously.
- To explore if alpha2-adrenergic receptors contribute to the sedative effect of Amitraz, another compound, Yohimbine, was administered with Amitraz.
- The antinociceptive effect was studied by applying heat and light onto the fetlock (ankle area) and withers (the ridge between the shoulder blades) of a horse as a pain stimulus and observing changes in hoof withdrawal reflex latency (HWRL) and skin twitch reflex latency (STRL).
- The compound dimethylformamide (DMF) was used as a control with no sedative or pain-relieving properties, while xylazine hydrochloride, a known sedative, was used as a positive control.
Findings
- Amitraz induced a dose-dependent relaxation of the horse’s neck muscles, suggesting a sedative effect.
- The HWRL increased significantly for all doses of Amitraz compared to DMF, up to 150 minutes after administration, indicating a potential antinociceptive (pain-relieving) effect.
- The STRL also significantly increased after administering the highest dose of Amitraz (0.15mg/kg), indicating a similar pain-relieving effect. This effect lasted up to two hours post-injection.
- However, lower doses of Amitraz (0.05 and 0.10 mg/kg) and the dose of Xylazine did not show significant antinociceptive effects in the STRL test.
Conclusions
- The findings suggest that Amitraz may act as a sedative and have pain-relieving properties when administered at specific doses.
- More research is needed to confirm these effects and explore their potential applications in veterinary medicine and treatment protocols.
Cite This Article
APA
Queiroz-Neto A, Zamur G, Gonçalves SC, Carregaro AB, Mataqueiro MI, Harkins JD, Tobin T.
(1998).
Characterization of the antinociceptive and sedative effect of amitraz in horses.
J Vet Pharmacol Ther, 21(5), 400-405.
https://doi.org/10.1046/j.1365-2885.1998.00150.x Publication
Researcher Affiliations
- Faculdade de Ciências Agrárias e Veterinárias, Câmpus de Jaboticabal, FCAV/UNESP, SP, Brazil.
MeSH Terms
- Adrenergic alpha-Agonists / administration & dosage
- Adrenergic alpha-Agonists / pharmacology
- Animals
- Dimethylformamide / administration & dosage
- Dimethylformamide / pharmacology
- Dose-Response Relationship, Drug
- Female
- Horses / physiology
- Hypnotics and Sedatives / pharmacology
- Injections, Intramuscular
- Pain Threshold / drug effects
- Receptors, Adrenergic, alpha-2 / drug effects
- Receptors, Adrenergic, alpha-2 / physiology
- Toluidines / administration & dosage
- Toluidines / pharmacology
- Xylazine / administration & dosage
- Xylazine / pharmacology
Citations
This article has been cited 9 times.- Madhuri P, Mukherjee A, Manna S, Dhar M. Amitraz poisoning: Early gastric lavage can prevent life-threatening complications.. J Family Med Prim Care 2020 Apr;9(4):2129-2131.
- Shilpakar O, Karki B, Rajbhandari B. Amitraz Poisoning - Tale of an Unusual Pesticide Poisoning: A Case Report.. JNMA J Nepal Med Assoc 2020 May 30;58(225):338-340.
- Bhartiya M, Hans B, Sundaray S, Sagar A. Amitraz Poisoning: The not so (Un)common Poisoning.. Cureus 2019 Aug 20;11(8):e5438.
- Saseedharan S, Pathrose EJ, Madhav BV. A Clinical Conundrum Called Amitraz Poisoning - A Case Report.. Indian J Crit Care Med 2018 Mar;22(3):195-196.
- Dhooria S, Agarwal R. Amitraz, an underrecognized poison: A systematic review.. Indian J Med Res 2016 Sep;144(3):348-358.
- Dhooria S, Behera D, Agarwal R. Amitraz: a mimicker of organophosphate poisoning.. BMJ Case Rep 2015 Oct 1;2015.
- Eizadi-Mood N, Sabzghabaee AM, Gheshlaghi F, Yaraghi A. Amitraz poisoning treatment: still supportive?. Iran J Pharm Res 2011 Winter;10(1):155-8.
- Cruz FS, Carregaro AB, Machado M, Antonow RR. Sedative and cardiopulmonary effects of buprenorphine and xylazine in horses.. Can J Vet Res 2011 Jan;75(1):35-41.
- Yilmaz HL, Yildizdas DR. Amitraz poisoning, an emerging problem: epidemiology, clinical features, management, and preventive strategies.. Arch Dis Child 2003 Feb;88(2):130-4.
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