THE USE OF YOHIMBINE IN THE TREATMENT OF AMITRAZ
INTOXICATION IN A HORSE: A CASE REPORT
Leandro S. Zechetto, Raquel Yvonne Arantes Baccarin, Wilson Roberto Fernandes,
Patrícia Miyashiro, Carla Bargi Belli
Introduction: Amitraz is a formamidine compound used as acaricide in many species,
but its use is prohibited in horses, although there are reports of its utilization as a
sedative at low doses. Amitraz intoxication leads to depression, ataxia and intestinal
hypomotility. In the literature, mostly symptomatic treatment is reported. Case Report:
One horse, male, crossbred, 9 years old, was refereed with a history of acute abdomen,
apathy and topical administration of amitraz the previous day. During examination, the
animal presented depression, moderate abdominal distension, intestinal atony, normal
peritoneal fluid, detection of fermented gastric contents during gastric lavage, and gas
distention of the large colon and cecum on rectal examination. On the first day, the
treatment was symptomatic (IV fluids and metoclopramide). On the second day, the
horse already demonstrated some signs of return of colon motility, and the treatment
with yohimbine was started at a 0.05 mg/kg IV dose, divided into two administrations in
a 4 hours interval. Soon after the first administration, there was already complete
reversion of apathy, and then a rapid establishment of the intestinal motility, with
normalization in less than 24 hours. Discussion: Although the efficacy of the utilization
of yohimbine (•2 adrenergic antagonist) in amitraz intoxication in various species is
known, in equine medicine there are only reports of its utilization to block the sedative
action of the compound. It is possible that the lack of use of this product is due to the
difficulty in access to the medication. This is not a problem anymore, however, because
of the availability of the manipulated product at an reasonable cost. The yohimbine dose
was half of that cited in the literature, because of the relatively mild signs presented by
the animal. Conclusions: The treatment with yohimbine of colic cases caused by amitraz
intoxication in horses helps in the recovery of the animal and is now available in our area
at a reasonable cost.
Hospital Veterinário USP/FMVZ, Av. Prof. Dr. Orlando Marques de Paiva, 87 Cidade Universitária, São
Paulo – SP Brasil, CEP: 05508-270; e-mail: [email protected]