Atrovet

The principal veterinary indications for systemic atropine include:

• Preanesthetic to prevent or reduce secretions of the respiratory tract
• Treat sinus bradycardia, sinoatrial arrest, and incomplete AV block
• Differentiate vagally-mediated bradycardia for other causes
• As an antidote for overdoses of cholinergic agents (e.g., physostigmine, etc.)
• As an antidote for organophosphate, carbamate, muscarinic mushroom, bluegreen
• algae intoxication
• Hypersialism
• Treatment of bronchoconstrictive disease

Do not use in patients with glaucoma, intestinal ileus, gastroparesis, or tachycardia.

Atropine, like other antimuscarinic agents, competitively inhibits acetylcholine or other cholinergic stimulants at postganglionic parasympathetic neuroeffector sites. High doses may block nicotinic receptors at the autonomic ganglia and at the neuromuscular junction. Pharmacologic effects are dose related. At low doses salivation, bronchial secretions, and sweating (not horses) are inhibited. At moderate systemic doses, atropine dilates and inhibits accommodation of the pupil, and increases heart rate. High doses will decrease GI and urinary tract motility. Very high doses will inhibit gastric secretion.

Atropine sulfate is well absorbed after oral administration, IM injection, inhalation, or endotracheal administration. After IV administration peak effects in heart rates occur within 3–4 minutes. Atropine is well distributed throughout the body and crosses into the CNS, across the placenta, and can distribute into the milk in small quantities

The following drug interactions have either been reported or are theoretical in humans or animals receiving atropine and may be of significance in veterinary patients:
The following drugs may enhance the activity or toxicity of atropine and its derivatives:
AMANTADINE
ANTICHOLINERGIC AGENTS (other)
ANTICHOLINERGIC MUSCLE RELAXANTS
ANTIHISTAMINES (e.g., diphenhydramine)
DISOPYRAMIDE
MEPERIDINE
PHENOTHIAZINES
PROCAINAMIDE
PRIMIDONE

TRICYCLIC ANTIDEPRESSANTS (e.g., amitriptyline, clomipramine)
ALPHA-2 AGONISTS (e.g.,dexmedetomidine, medetomidine): Use of atropine with alpha-2 blockers may significantly increase arterial blood pressure, heart rates and the incidence of arrhythmias (Congdon et al. 2009). Clinical use of atropine or glycopyrrolate to prevent or treat medetomidineor dexmedetomidine-caused bradycardia is controversial and many discourage using together. This may be particularly important when using higher dosages of the alpha-2 agonist.
AMITRAZ: Atropine may aggravate some signs seen with amitraz toxicity; leading to hypertension and further inhibition of peristalsis
ANTACIDS: May decrease PO atropine absorption; give oral atropine at least 1 hour prior to oral antacids
CORTICOSTEROIDS (long-term use): may increase intraocular pressure
DIGOXIN (slow-dissolving): Atropine may increase serum digoxin levels; use regular digoxin tablets or oral liquid
KETOCONAZOLE: Increased gastric pH may decrease GI absorption; administer oral atropine 2 hours after ketoconazole
METOCLOPRAMIDE: Atropine and its derivatives may antagonize the actions of metoclopramide

Side effects include xerostomia, ileus, constipation, tachycardia, and urine retention

Use high doses (e.g., 0.04 mg/kg) cautiously because it increases oxygen demand.