Glycopyrrolate

Glycopyrrolate is a quaternary ammonium antimuscarinic used mainly in anesthesia and cardiovascular support. It reduces peripheral vagal effects and selected secretions while entering the central nervous system poorly. Its principal veterinary roles are treatment of clinically important vagally mediated bradycardia and selective use as an anesthetic adjunct in dogs, cats and other species.

Group

Antimuscarinic

Mechanism of Action

Glycopyrrolate competitively blocks acetylcholine at peripheral muscarinic receptors. Cardiac receptor blockade reduces vagal slowing of sinoatrial activity and atrioventricular conduction, increasing heart rate in responsive bradyarrhythmias. Blockade in secretory glands reduces salivary and respiratory secretions. Its charged quaternary structure limits passage across the blood–brain barrier and therefore limits direct central antimuscarinic effects.

Dose Rates

Dog

Use / stage	Dose	Route	Schedule	Instructions
Vagal effects during anesthesia	0.005–0.01 mg/kg	IV, IM, SC		Do not use in: Glaucoma, Ileus, Tachycardia

Cat

Use / stage	Dose	Route	Schedule	Instructions
Vagal effects during anesthesia	0.005–0.01 mg/kg	IV, IM, SC		Do not use in: Glaucoma, Ileus, Tachycardia

Cattle

Use / stage	Dose	Route	Schedule	Instructions
Vagal effects during anesthesia	0.005–0.01 mg/kg	IM, SC		Do not use in: Glaucoma, Ileus, Tachycardia
Vagal effects during anesthesia	0.0025–0.005 mg/kg	IV		Do not use in: Glaucoma, Ileus, Tachycardia

Horse

Use / stage	Dose	Route	Instructions
Vagal effects during anesthesia	0.005–0.01 mg/kg	IM, SC	Do not use in: Glaucoma, Ileus, Tachycardia
Vagal effects during anesthesia	0.0025–0.005 mg/kg	IV	Do not use in: Glaucoma, Ileus, Tachycardia
Imidocarb muscarinic adverse effects	0.0025 mg/kg	IV
Bronchodilation	Reference only	IM	Initial example for a 450 kg horse: 2–3 mg two to three times daily. Retained as a weight-qualified example, not a universal fixed dose.

Ferret

Use / stage	Dose	Route	Schedule	Instructions
Anesthetic premedication	0.01 mg/kg	SC, IM
Anesthetic premedication	0.01–0.02 mg/kg	IM, IV

Rabbit

Use / stage	Dose	Route	Schedule	Instructions
Vagal bradycardia and secretion reduction	0.01–0.1 mg/kg	IM, SC
Vagal bradycardia and secretion reduction	0.01 mg/kg	IV

Reptile

Use / stage	Dose	Route	Schedule	Instructions
Anesthetic bradycardia	0.01 mg/kg	IM, IV		For profound or prolonged bradycardia; intracelomic administration is also described but is not a supported route code.

Indications

Treatment of clinically significant vagally mediated sinus bradycardia or selected vagal conduction disturbances in veterinary patients.
Selective preanesthetic or intraoperative reduction of excessive salivary and airway secretions.
Prevention of peripheral muscarinic effects when an acetylcholinesterase inhibitor is used to reverse nondepolarizing neuromuscular blockade.

Contraindications

Glaucoma, ileus, gastroparesis or tachycardia

Interactions

Opposes cholinergic prokinetic/secretory drugs.

Adverse effects

Dry mouth, constipation, ileus, tachycardia and urinary retention

Preparations

Preparation	Form	Strength	Route
Glycopyrrolate injection 0.2 mg/mL	Injection	0.2 mg / mL	IV, IM, SC

Monitoring and Administration

Monitor heart rate and rhythm. Routine treatment of alpha-2-agonist-associated bradycardia is usually unnecessary.

The source also mentions 1 mg per horse without a specific route for that fixed amount.