Nizatidine
Nizatidine is an **H2-receptor antagonist** structurally and pharmacologically similar to ranitidine. While it possesses acid-suppressing capabilities like cimetidine and famotidine, its primary utility in veterinary medicine (particularly small animal practice) stems from its **prokinetic properties**. * Used to manage delayed gastric emptying, intestinal pseudo-obstruction, and feline constipation/megacolon. * May help prevent hemorrhagic necrosis in feline pancreatitis. > **Clinical Pearl:** Nizatidine is less commonly used today due to the availability of more potent acid suppressants (like proton pump inhibitors) and other prokinetics, but it remains a viable option, especially when dual acid-suppressing and prokinetic action is desired.
Mechanism: * **Acid Suppression:** Competitively inhibits histamine at the **H2 receptors** on gastric parietal cells → reduces basal and stimulated gastric acid output → decreases pepsin secretion. * **Prokinetic Action:** Inhibits **acetylcholinesterase** → prevents breakdown of acetylcholine → increases acetylcholine concentrations at **muscarinic receptors** → stimulates GI motility. * May also exert direct agonist effects on **M3 muscarinic receptors**. * Increases lower esophageal sphincter (LES) pressure.
Dosing by species
- As a colonic prokinetic agent · 2.5-5 mg/kg PO once daily · PO · once daily
- As a colonic prokinetic agent (in combination with cisapride) · 2.5-5 mg/kg PO q12h · PO · q12h · Used in combination with cisapride
- As a prokinetic agent · 2.5-5 mg/kg PO once daily · PO · once daily
- As an H2 blocker to reduce gastric acid production · 5 mg/kg PO once daily · PO · once daily · Dosage not well established
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Routes of administration
Contraindications
- Hypersensitivity to nizatidine
Adverse effects
- Anemia (rare)
- Headache/dizziness (rare)
- Rash/pruritus (rare)
- Cholinergic effects at high doses
Drug interactions
- Anticholinergic agents (atropine, propantheline) · May negate the prokinetic effects of nizatidine
- Aspirin (and other salicylates) · May increase salicylate levels in patients receiving high doses of aspirin
Monitoring
- Clinical efficacy (decrease in symptoms, endoscopic examination, blood in feces)
- Serum ALT values (in high dose, chronic therapy)
Overdose
Single oral doses up to 800 mg/kg were not lethal in dogs. Overdose may cause cholinergic effects (lacrimation, salivation, emesis, miosis, diarrhea). Treat supportively and symptomatically.
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.