Xylazil-100 produces dose dependent sedation and analgesia through an alphamimetic and direct opioid effect. It also produces muscle relaxation by inhibition of the intraneuronal transmission of impulses centrally in the CNS.

Onset of action after intravenous injection is rapid with effective sedation present within 3-5 minutes and after intramuscular or subcutaneous administration. It occurs within 10-15 minutes. The sedative effect usually lasts 1-2 hours, while the analgesic effect lasts only 30-40 minutes. The analgesic effect in the horse is not as profound as in cattle. The usual response to Xylazil-100 administration in the horse is drooping of the head, ataxia without recumbency, penile prolapse which does not progress to paraphimosis and pendulous lower lip.  Complete recovery varies with the dose administered, however, it is usually uneventful and requires minimal supervision.

It is normal for Xylazil-100 to cause cardiopulmonary depression manifested by a decrease in heart rate, stroke volume, cardiac output and respiratory rate together with an increase in total peripheral resistance. These effects are transitory and of no clinical significance in healthy horses. However, it is not recommended to use Xylazil-100 where there is cardiovascular disease including conditions of shock or respiratory depression.

A number of cardiac dysrhythmias such as second degree atrioventricular blocks have been encountered with xylazine administration and it is believed that increased vagal tone is responsible for these. Premedication with atropine sulphate will help prevent their occurrence although care must be taken, as atropine sulphate is known to be associated with colic in the Horse.

Xylazil-100 should not be administered to mares in the last trimester of pregnancy as it may precipitate an early parturition of abortion due to its oxytocic effect on the uterus.

Xylazil-100 should not be administered intra-arterially.

Painful stimuli may cause an apparently deeply sedated patient to react inappropriately and therefore adequate care should be taken.

       Storage