Short communication
Effect of amitraz on heart rate and aortic blood pressure in conscious dogs: Influence of atropine, prazosin, tolazoline, and yohimbine

https://doi.org/10.1016/0041-008X(86)90150-XGet rights and content

Abstract

The effect of amitraz on heart rate (HR) and mean aortic blood pressure (MAP) were studied in five conscious male dogs. An iv injection of amitraz (1 mg/kg) caused a decrease in HR, which was accompanied by sinus arrhythmia for at least 60 min. Administration of amitraz also caused an increase in MAP for 20 min. Atropine sulfate (0.045 mg/kg, iv) increased HR and prevented amitraz-induced bradycardia. In addition, atropine potentiated amitraz-induced hypertension for 45 min. Yohimbine, and α2-adrenoreceptor antagonist, given iv at 0.1 mg/kg, prevented hypertension, bradycardia, and sinus arrhythmia induced by amitraz. Tolazoline, a nonselective α-adrenoreceptor antagonist, given iv at 5 mg/kg, reduced the bradycardia and sinus arrhythmia caused by amitraz administration but did not change amitraz-induced hypertension. Tolazoline alone also increased both HR and MAP. Prazosin, an α1-adrenoreceptor antagonist, given iv at 1 mg/kg, did not affect the cardiovascular actions of amitraz. The results suggest that (1) α2-adrenoreceptors mediate amitraz-induced bradycardia and hypertension, and (2) yohimbine, but not atropine, can be used to control the untoward reactions of amitraz.

References (12)

  • W.H. Hsu et al.

    Effect of amitraz and chlordimeform on heart rate and pupil diameter in rats: Mediated by α2-adrenoreceptors

    Toxicol. Appl. Pharmacol

    (1984)
  • D.M. Clark et al.

    Cardiopulmonary responses to xylazine/ketamine anesthesia in the dog

    J. Amer. Anim. Hosp. Assoc

    (1982)
  • V.S. Dobozy

    Mitaban safety

    DVM

    (1982)
  • H. Farmer et al.

    The use of amitraz (N′-2,4(dimethylphenyl)-N-[((2,4-dimethylphenyl)imino)-methyl]-N-methylmethanimidamide) in demodecosis in dogs

    Aust. Vet. J

    (1980)
  • F.L. Gobel et al.

    The rate-pressure product as an index of myocardial oxygen consumption during exercise in patients with angina pectoris

    Circulation

    (1978)
  • W.H. Hsu et al.

    Amitraz-induced delay of gastrointestinal transit in mice: Mediated by α2-adrenergic receptors

    Drug Dev. Res

    (1984)
There are more references available in the full text version of this article.

Cited by (52)

  • Neurotoxicity of amitraz, a formamidine pesticide

    2020, Advances in Neurotoxicology
    Citation Excerpt :

    However, findings in human also indicate possible miosis following amitraz intoxication (see following section). Clonidine has been used for over 40 years to treat hypertension (Pettinger, 1975), and some studies in animals have reported hypotension following administration of amitraz (Andrade and Sakate, 2003); however, hypertension has also been found (Cullen and Reynoldson, 1988; Hsu et al., 1986), and both opposite effects on blood pressure appear to be mediated by alpha2-adrenoceptors (Table 3). CNS effects are among the primary effects observed after administration of amitraz (Table 3), with the most relevant one being sedation, which also represents a main effect of clonidine and other alpha-2 adrenoceptor agonists (Hayes et al., 1986; Sinclair, 2003).

  • Amitraz

    2018, Veterinary Toxicology: Basic and Clinical Principles: Third Edition
  • Amitraz

    2012, Small Animal Toxicology, Third Edition
  • Amitraz

    2012, Veterinary Toxicology: Basic and Clinical Principles
  • Amitraz

    2012, Veterinary Toxicology
  • Amitraz

    2007, Veterinary Toxicology: Basic and Clinical Principles
View all citing articles on Scopus
2

A visiting professor from College of Veterinary Medicine, Beijing Agricultural University, Beijing, People's Republic of China.

View full text