Title page for ETD etd-01052007-110131

Document Type Doctoral Thesis
Author Mogoa, Eddy Geoffrey Mosoti
URN etd-01052007-110131
Document Title Effects of environmental temperature on pharmacokinetics of, and clinical response to xylazine in goats
Degree DPhil (Surgery)
Department Companion Animal Clinical Studies
Advisor Name Title
Prof G F Stegmann
  • goats
  • drugs metabolism
  • pharmacokinetics
  • temparature physiological effect
Date 1999-05-01
Availability unrestricted
The clinical use of xylazine may result in morbidity and mortality in small ruminants, and it was suspected that exposure to changes in environmental temperature may contribute to these effects.

Xylazine hydrochloride was administered intravenously at a dose of 0.1 mg/kg to a group of six indigenous domestic goats with a mean body mass of 28.2 kg. Xylazine was administered at a room temperature of 14C and relative humidity of 33%, at 24C and a relative humidity of 55%, and at 34C with a relative humidity of 65%. The following variables were evaluated: clinical behaviour, cardiopulmonary function, haematology, acid-base balance, plasma glucose and insulin, body temperature, and the pharmacokinetic characteristics of xylazine.

Xylazine administration resulted in transient restlessness, followed by sedation, muscle relaxation, and salivation. The onset of these clinical signs was not influenced by environmental conditions.

Administration of xylazine resulted in a transient increase in respiratory rate in the 24 and 34C environments. In the 14C environment, the respiratory rate decreased significantly (p<0.05) from baseline and continued to decrease for the full duration of the 60 minutes observation period. Heart rate decreased in all three environments, but this decrease was only significant in the 14C environment for the duration of the observation period.

Changes in haemoglobin concentration, haematocrit, red blood cell count and mean red blood cell volume were significantly (p<0.05) different 15 minutes after xylazine administration and continued to be so for the duration of the observation period. Total serum protein changed significantly (p<0.05) in the 24 and 34C environments from 15 minutes after xylazine administration. The white cell count changed significantly (p<0.05) from 15 minutes after xylazine administration for the duration of the observation period in all three environments.

Significant (p<0.05) changes occurred after xylazine administration in acid-base balance and arterial blood gas variables independent of environmental conditions. Arterial pH and the partial pressure of oxygen decreased significantly within 5 minutes of xylazine administration, and the partial pressure of carbon dioxide, total carbon dioxide and base excess increased significantly (p<0.05).

Environmental conditions had no observable on plasma glucose and insulin concentration. Significant (p<0.05) changes occurred in all three environments.

Environmental conditions had no influence on body temperature in the control (untreated) animals. Following the administration of xylazine, the body temperature of the goats in the 14 and 24C environments was significantly (p<0.05) lower than that of the goats in the 34C environment. The maximum decrease in oesophageal temperature of 1.57C was observed 60 minutes after xy1azine administration to goats maintained in the 14C environment.

Environmental conditions had no influence on all of the pharrnacokinetic parameters of xylazine hydrochloride evaluated.

It is concluded that apart from changes in body temperature, changes that occurred in clinical and pharmacokinetic variables after xylazine administration, were independent of the three environmental temperature and humidity conditions.

1999, University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria.

Please cite as follows:

Mogoa, EGM 1999, Effects on environmental temperature on pharmacokinetics of, and clinical response to xylazine in coats, DPhil thesis, University of Pretoria, Pretoria, viewed yymmdd < http://upetd.up.ac.za/thesis/available/etd-01052007-110131/ >


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