Emesis occurs occasionally in dogs, and frequently in cats, soon after the administration of xylazine, but before clinical sedation is evident. When observed, emesis usually occurs only a single time, after which there is no further emetic effect. The use of anti-emetics may delay this phenomenon. The occurrence of emesis may be considered a desirable effect when xylazine is administered as a pre-anesthetic to general anesthesia.
Xylazine used at the recommended dosage levels may occasionally cause slight muscle tremors, bradycardia with partial A-V heart block and a reduced respiratory rate. Should excessive respiratory depression or bradycardia occur following the use of AnaSed® (xylazine), administer yohimbine to rapidly reverse the xylazine-induced effects.
Gaseous extension of the stomach may occur in dogs treated with xylazine making radiographic interpretation more difficult.
Movement in response to sharp auditory stimuli may be observed.
Increased urination may occur in cats following the use of xylazine.
Clinical results with xylazine have not revealed any detrimental effects when the compound is administered to pregnant dogs or cats. However, until more definitive studies are completed, xylazine is not recommended for use in these animals.
Careful consideration should be given before administering to dogs or cats with significantly depressed respiration, severe pathologic heart disease, advanced liver or kidney disease, severe endotoxic or traumatic shock and stress conditions such as extreme heat, cold, or fatigue.
Analgesic effect is variable, and depth should be carefully assayed prior to surgical/clinical procedures. In spite of sedation, the practitioner and handlers should proceed with caution since defense reactions may not be diminished.
Do not use xylazine in conjunction with tranquilizers.
Since an additive effect results from the use of xylazine and the barbiturate compounds, it should be used with caution with these central nervous system depressants. Products known to produce respiratory depression or apnea, such as thiamylal sodium, should be given at a reduced dosage and, when injected intravenously, should be administered slowly.
When intravenous administration is desired, avoid perivascular injection in order to achieve the desired effect. Studies have shown negligible evidence of tissue irritation, however, following the perivascular injection of xylazine.
Bradycardia and an arrhythmia in the form of incomplete atrioventricular block have been reported following xylazine administration. Although clinically the importance of this effect is questioned, a standard dose of atropine given prior to or following xylazine will greatly decrease the incidence.
While sedation usually lasts from 1 to 2 hours, recovery periods in excess of 4 to 5 hours have been reported in dogs and cats.
Xylazine has been tested in dogs at 4 times the recommended dose. Doses of this magnitude produced muscle tremors, emesis and long periods of sedation.4