Anticholinergics as Preanaesthetic
Anticholinergics like Atropine, Glycopyrolate and Pyrolate are used as preanaesthetic because of their anti secretory actions (Decrease Gastro intestinal and Respiratory tract secretions).
Atropine
Atropine decrease the oral, pharyngeal and respiratory tract secretions.
Atropine dilates bronchi and increase both anatomic and physiologic dead space.
Atropine suppresses the vagal influence on the heart, relaxes the sphincter muscle of iris, dilating the pupil.
Atropine decreases tear formation in both awake and anaesthetic dogs.
It can be given S/C, I/M and I/V.
Atropine when given I/V, there is an increase in vagal tone both centrally and peripherally, initially. The classic parasympatholytic action occurs secondarily.
Contraindicated in patients with pre-existing tachycardia (fever and the thyrotoxicosis).
Rat and rabbit can destroy large quantities of atropine because they have the atropine esterase enzyme in the liver.
Read more about Atropine (Dose, Contraindication, Mechanism of Action and Toxicity) for animals>
Glycopyrolate
Glycopyrolate is a synthetic quartenary ammonium anticholinergic. It have longer duration of action than atropine.
Glycopyrolate blocks vagal reflexes during induction of anaesthesia and intubation.
Dose of Glycopyrolate: 0.01 mg/kg body weight IM SC IV