Aminopentamide
Aminopentamide is a veterinary-specific **anticholinergic and antispasmodic** agent historically used to manage acute abdominal visceral spasms, pylorospasm, hypertrophic gastritis, and associated nausea, vomiting, or diarrhea in dogs and cats. > **Clinical Pearl:** While once common, the use of systemic anticholinergics for non-specific GI upset has largely been superseded by more targeted antiemetics (e.g., maropitant, ondansetron) and prokinetics, due to the risk of inducing ileus and systemic side effects.
Mechanism: Aminopentamide acts as a **competitive antagonist at muscarinic acetylcholine receptors (mAChRs)** in the parasympathetic nervous system. By blocking acetylcholine binding, it inhibits parasympathetic tone. * **GI Tract:** → Decreases smooth muscle contractions (reducing colonic spasms) and reduces gastric acid secretion. * **Systemic:** Compared to atropine, it reportedly has a greater targeted effect on reducing colonic contractions with relatively fewer mydriatic (pupil dilating) and salivary (dry mouth) effects, though classic anticholinergic signs can still occur.
Dosing by species
- Acute abdominal visceral spasm, nausea, vomiting, diarrhea · 10 lbs or less: 0.1 mg; 11-20 lbs: 0.2 mg; 21-50 lbs: 0.3 mg; 51-100 lbs: 0.4 mg; over 100 lbs: 0.5 mg. If desired effect is not attained, dosage may be gradually increased up to 5 times these amounts. · PO, IM, SC · q8-12h
- Second-line adjunctive therapy for refractory IBD · 0.1-0.4 mg/kg · SC · BID-TID
- Acute abdominal visceral spasm, nausea, vomiting, diarrhea · 10 lbs or less: 0.1 mg; 11-20 lbs: 0.2 mg; 21-50 lbs: 0.3 mg; 51-100 lbs: 0.4 mg; over 100 lbs: 0.5 mg. If desired effect is not attained, dosage may be gradually increased up to 5 times these amounts. · PO, IM, SC · q8-12h
- To decrease tenesmus in malabsorption/maldigestion syndromes · 0.1-0.4 mg (total dose) · SC, IM · BID-TID
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Routes of administration
Contraindications
- Glaucoma (absolute contraindication)
- Pyloric obstruction
- Hypersensitivity to anticholinergic drugs
- Tachycardias secondary to thyrotoxicosis or cardiac insufficiency
- Myocardial ischemia
- Unstable cardiac status during acute hemorrhage
- GI obstructive disease
- Paralytic ileus
- Severe ulcerative colitis
- Obstructive uropathy
- Myasthenia gravis (unless used to reverse adverse muscarinic effects)
- Known or suspected GI infections (e.g., parvovirus enteritis)
Adverse effects
- Dry mouth (xerostomia)
- Dry eyes (keratoconjunctivitis sicca)
- Blurred vision (mydriasis)
- Urinary hesitancy or retention
- Tachycardia
- Decreased GI motility (constipation/ileus)
Drug interactions
- Antihistamines · May enhance the activity of anticholinergic derivatives
- Procainamide · May enhance the activity of anticholinergic derivatives
- Quinidine · May enhance the activity of anticholinergic derivatives
- Meperidine · May enhance the activity of anticholinergic derivatives
- Benzodiazepines · May enhance the activity of anticholinergic derivatives
- Phenothiazines · May enhance the activity of anticholinergic derivatives
- Primidone · May potentiate the adverse effects of anticholinergic derivatives
- Disopyramide · May potentiate the adverse effects of anticholinergic derivatives
- Nitrates · May potentiate the adverse effects of anticholinergic derivatives
- Corticosteroids (long-term use) · May increase intraocular pressure
- Nitrofurantoin · Anticholinergic derivatives may enhance actions
- Thiazide Diuretics · Anticholinergic derivatives may enhance actions
- Sympathomimetics · Anticholinergic derivatives may enhance actions
Monitoring
- Clinical efficacy (resolution of spasms, vomiting, or diarrhea)
- Heart rate (monitor for tachycardia)
- Urination frequency and volume (monitor for urinary retention)
- Eye moisture and pupil size
Overdose
No specific information was located regarding acute overdosage clinical signs or treatment for aminopentamide. Guidelines for atropine overdose may be applied: * **Decontamination:** If recent oral ingestion, empty gut contents and administer activated charcoal and saline cathartics. * **Supportive Care:** Treat clinical signs symptomatically. Fluid therapy and standard treatments for shock may be instituted. **Do not use phenothiazines** as they may contribute to anticholinergic effects. * **Antidote (Severe Cases):** The use of physostigmine is controversial and reserved for extreme agitation or life-threatening supraventricular/sinus tachycardias. Human pediatric dose (reasonable for small animals): 0.02 mg/kg slow IV, repeat q10 minutes until reversal of toxic effects. Physostigmine adverse effects (bronchoconstriction, bradycardia, seizures) may be treated with small doses of IV atropine.
VetSheet drug reference is intended for licensed veterinary professionals as a clinical decision-support aid, not a substitute for professional judgement or the manufacturer’s current label.