Premedication Premedication

Acepromazine can be given in low doses (0.02-0.05 mg/kg i.m.) but should not be used in the presence of cardiovascular disease such as endocardiosis and congestive heart failure, as it can cause rapid hypotension. Acepromazine should also be avoided in dogs prone to seizures, and it is contraindicated in the presence of renal impairment. Intravenous administration can cause profound hypotension and it should only be used by this route with great care. The author has witnessed a geriatric dog collapsing and dying immediately following the intravenous administration of acepromazine.

Xylazine and medetomidine should only be used with extreme care in geriatric canine and feline patients because they can cause deep and prolonged sedation with bradycardia and severe cardiovascular depression. Vomiting often follows their administration and this could result in aspiration in old animals with impaired laryngeal reflexes. Caution is needed when using these substances in the presence of pulmonary disease.

In dogs neuroleptanalgesics have the advantage that the narcotic component can be reversed by an antagonist. However they have proeffects on the cardiovascular and respiratory systems causing tachycardia or bradycardia, hypertension or hypotension, depressed respiration and cyanosis. After reversal some dogs relapse into a sedated state that may last for up to 36 hours.

These agents are contraindicated in the presence of impaired hepatic or renal function, should only be used at reduced dose rates (50% that recommended for adults) and with great care in elderly patients. When using narcotic analgesics or neuroleptanalgesics dogs should be premeditated with anticholinergics to avoid secondary bradycardia.