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Evaluation of threshold doses of drug action in the horse using hematocrit values as an indicator.
Abstract: This study was designed to explore the use of hematocrit values as possible indicators of the threshold doses of adrenergic drugs in the performance horse. Acepromazine, detomidine, and fluphenazine were tested for their effects on hematocrit values, with the threshold dose for these effects investigated. Hematocrit values were shown to be quite sensitive to the administration of acepromazine with doses as low as 50 micrograms/horse producing detectable depressions in hematocrit values for up to 2 hours. Increasing the dose increased the magnitude of the effect, but did not appear to prolong it, while in contrast, reducing the dose to below 25 micrograms/horse totally eliminated the effect. The alpha-2 agonist detomidine produced a similar depression in hematocrit values, although doses of 10 micrograms/kg or approximately 5 mg/horse, were needed to produce a measurable effect. The anti-psychotic fluphenazine, which is believed to be an illegally administered drug in race horses, had no significant effect on hematocrit values when comparable doses were administered. In addition, the results of monitoring the hematocrit values of six horses for 48 hours suggested that the variations seen may be partially related to circadian factors, with peak values occurring in the afternoon hours.
Publication Date: 1992-02-01 PubMed ID: 1570406 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
- Research Support
- Non-U.S. Gov't
Summary
This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.
The research investigates how administration of certain drugs affects the hematocrit values in horses and uses these values to determine the threshold doses of these drugs. The drugs in question include acepromazine, detomidine, and fluphenazine.
Objective and Hypothesis
- The researchers intended to assess if hematocrit values in horses can be used as indicators for the minimum effective doses of certain adrenergic drugs.
- The hypothesis was that the administration of the selected drugs causes changes in hematocrit values, thus aiding in the identification of their respective threshold doses.
Methodology
- The study involved testing acepromazine, detomidine, and fluphenazine on horses and observing the changes in hematocrit values.
- The examination determined the lowest dose of these drugs that induced noticeable changes in the horses’ hematocrit values.
Findings
- The study found that hematocrit values are sensitive to the administration of acepromazine, with detectable changes occurring with a dose as low as 50 micrograms per horse.
- The magnitude of the effect on hematocrit values increased with the dose, but the duration of the effect remained steady. Below 25 micrograms per horse, the drug seemed to have no effect at all.
- The drug detomidine had a similar effect on hematocrit values, although it required a larger dose of about 10 micrograms/kg (roughly 5 milligrams per horse) to produce a measurable effect.
- Fluphenazine, an antipsychotic drug often suspected to be used illegally on racing horses, showed no significant effect on hematocrit values at comparable doses.
Additional Observations
- The study observed six horses for forty-eight hours following drug administration to monitor the change in hematocrit values due to circadian rhythm.
- The researchers found that peak hematocrit values occurred in the afternoon, suggesting that time of day may influence these values.
Conclusion
- The researchers concluded that hematocrit values can be used as one of the potential indicators to determine the threshold doses of acepromazine and detomidine in horses.
- The study, however, did not find a similar correlation for the antipsychotic fluphenazine.
Cite This Article
APA
Wood T, Stanley S, Woods WE, Henry P, Watt D, Tobin T.
(1992).
Evaluation of threshold doses of drug action in the horse using hematocrit values as an indicator.
Res Commun Chem Pathol Pharmacol, 75(2), 231-241.
Publication
Researcher Affiliations
- Maxwell H. Gluck Equine Research Center, Department of Veterinary Science, University of Kentucky, Lexington 40546-0099.
MeSH Terms
- Acepromazine / administration & dosage
- Analysis of Variance
- Animals
- Female
- Fluphenazine / administration & dosage
- Hematocrit / veterinary
- Horses / blood
- Imidazoles / administration & dosage
- Injections, Intravenous
Citations
This article has been cited 2 times.- Mehrazin H, Sakha M, Safi S. Effects of Age, Sex, and Exercise on Measurement of Serum CTnI Levels and Some Parameters Related to the Cardiovascular Capacity of Caspian Horses. Vet Med Sci 2025 Mar;11(2):e70202.
- Volpato J, Mattoso CR, Beier SL, Coelho MM, Tocheto R, Kirsten CE, Yonezawa LA, Saito ME. Sedative, hematologic and hemostatic effects of dexmedetomidine-butorphanol alone or in combination with ketamine in cats. J Feline Med Surg 2015 Jun;17(6):500-6.
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