Ranitidine: veterinary dose and monograph

At a glance

Drug class

Gastrointestinal

Also known as

Zinetac, Rantac, Aciloc, Zantac

Species with doses

Dogs, Cats, Horses, Rabbits and Primates

General dose range

1–2 mg/kg PO q8–12h — check the species tables for the indication

Routes

PO, IV

Last reviewed

1 October 2026

Indications

• Gastric / duodenal ulceration and erosive gastritis
• Oesophagitis / gastro-oesophageal reflux
• Hypersecretory states (e.g. mast cell tumour–associated, gastrinoma) — adjunct
• Mild prokinetic support (gastric emptying / ileus, adjunct)

Ranitidine dose by species

Doses are per administration unless stated. mg/kg doses scale with body weight; per-animal, per-quarter and infusion-rate doses are shown as the reference writes them.

Dogs

• Acid suppression / ulcer / prokinetic: Papich 5e: 2 mg/kg q8h IV or PO. Plumb’s p.1040: ulcer disease 0.5–2 mg/kg PO, IV or IM q8–12h (Haskins); 2 mg/kg q8–12h; oesophagitis 1–2 mg/kg twice daily; prokinetic 1–2 mg/kg PO q12h. Give IV slowly. A PPI is more effective for significant ulceration.

Cats

• Acid suppression / gastritis: Papich 5e: 2.5 mg/kg q12h IV or 3.5 mg/kg q12h PO. Plumb’s p.1040: 2.5 mg/kg IV or 3.5 mg/kg PO q12h (Matz); 1–2 mg/kg PO, IV or SC q12h (Sellon); colonic prokinetic 1–2 mg/kg PO q8–12h.

Horses

• Gastric ulceration (adjunct): Papich 5e: 2.2–6.6 mg/kg q6–8h PO — 6.6 mg/kg suppresses acid more effectively. Plumb’s p.1040: 6.6 mg/kg PO q8h (Sanchez; Paradis — foals often with omeprazole). Omeprazole is first-line for EGUS. ARCI Class 5.
• Gastric ulceration (IV): Papich 5e: 2 mg/kg q6–8h IV. Plumb’s p.1040: 1.5–2 mg/kg IV or IM q6–8h (Sanchez 2004); foals 1.5 mg/kg IV q8h.

Rabbits

• Suspected gastric ulceration: Plumb’s p.1040: 2–5 mg/kg PO twice daily (Bryan 2009); as a prokinetic 0.5 mg/kg IV q24h with cisapride (Lichtenberger 2008).

Primates

• Gastric / duodenal ulcer (monkeys): Carpenter Exotic Animal Formulary 6th ed, Table 13-7 (p.711): monkeys 0.5 mg/kg PO q12h; chimpanzees 150 mg/animal PO q8–12h.

Contraindications

Known hypersensitivity. Significant renal impairment (reduce dose — renally excreted). Awareness of the NDMA-contamination regulatory status of the product source. PPIs are usually more effective for serious ulceration.

Species-specific warnings

Horses: For equine gastric ulcer syndrome, omeprazole is first-line; ranitidine is a less-effective alternative requiring frequent (q8h) dosing.

Adverse effects

• Generally well tolerated
• Occasional GI upset
• Bradycardia/hypotension with rapid IV injection
• Rare: thrombocytopenia, raised liver enzymes

Drug interactions

• Drugs needing acid for absorption (ketoconazole, itraconazole): reduced absorption
• Antacids: separate dosing (reduced ranitidine absorption)
• Minimal CYP inhibition (unlike cimetidine) — fewer interactions
• May alter absorption of pH-dependent drugs

Pregnancy and lactation

Generally considered acceptable in pregnancy/lactation (long human safety record), subject to product NDMA status.

Monitoring

• Clinical response (resolution of vomiting/melaena/regurgitation)
• Renal function (dose in impairment)
• Consider switching to a PPI for inadequate response or serious ulceration

Toxicity and overdose

Wide safety margin; overdose is usually limited to mild effects, with rapid IV injection occasionally causing bradycardia/hypotension. The main contemporary concern is the NDMA (nitrosamine) impurity issue that led to product recalls, rather than acute pharmacologic toxicity.

Management: Supportive; no specific antidote. Slow/stop IV for bradycardia/hypotension. Effects are generally minor and self-limiting.

Clinical pearls

• A mild acid-suppressant with a bonus prokinetic effect — but PPIs (omeprazole) suppress acid more effectively for real ulcers
• Fewer drug interactions than cimetidine (minimal CYP inhibition)
• Be aware many ranitidine products were withdrawn over NDMA contamination — check the source/regulatory status
• Give IV slowly to avoid bradycardia/hypotension; separate from drugs that need stomach acid to absorb (azoles)

Mechanism of action

Competitively blocks histamine H2 receptors on gastric parietal cells, reducing histamine-stimulated gastric acid secretion (basal and stimulated) and raising gastric pH to allow mucosal healing. Separately, ranitidine inhibits acetylcholinesterase, mildly enhancing cholinergic gut motility — the basis of its modest prokinetic effect not shared by other H2-blockers.

Formulations and products

• 150 mg tablet
• 300 mg tablet
• Syrup 15 mg/mL
• Injection 25 mg/mL
• Rantac — 150 / 300 mg tablet; 25 mg/mL injection, Tablet / injection (human-label)
• Zinetac / Aciloc — 150 / 300 mg tablet, Tablet (human-label)

Storage

Tablets/syrup/injection: 15–30 °C, protect from light; note product NDMA/recall status.

Before you use this dose

Reference doses for veterinary professionals. Confirm the dose against the product label, the patient’s condition, current guidance and local regulations before use; the attending veterinarian remains responsible for every clinical decision.

Other gastrointestinal drugs

• Mirtazapine
• Misoprostol
• Omeprazole
• Pantoprazole
• S-Adenosylmethionine (SAMe)
• Silymarin (Milk Thistle / Silybin)
• Sucralfate
• Sulfasalazine

Frequently asked questions