# Ranitidine: veterinary dose and monograph

> Ranitidine is a veterinary gastrointestinal drug. Histamine H2-receptor antagonist that reduces gastric acid secretion — used for gastritis, gastric/duodenal ulceration, oesophagitis and reflux, and (uniquely among H2-blockers) it has a mild PROKINETIC effect via anticholinesterase… Indications include gastric / duodenal ulceration and erosive gastritis; oesophagitis / gastro-oesophageal reflux; hypersecretory states (e.g. mast cell tumour–associated, gastrinoma) — adjunct. This monograph lists 6 reference doses for dogs, cats, horses, rabbits and primates, each with route, frequency and source.

Source: https://vetmasterji.com/drugs/ranitidine · Last reviewed: 2026-10-01

## 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

*Ranitidine doses for dogs*

| Indication | Dose | Route | Frequency | Duration |
| --- | --- | --- | --- | --- |
| Acid suppression / ulcer / prokinetic | 1–2 mg/kg | PO | q8–12h | — |

- 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

*Ranitidine doses for cats*

| Indication | Dose | Route | Frequency | Duration |
| --- | --- | --- | --- | --- |
| Acid suppression / gastritis | 1–3.5 mg/kg | PO | q12h | — |

- 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

*Ranitidine doses for horses*

| Indication | Dose | Route | Frequency | Duration |
| --- | --- | --- | --- | --- |
| Gastric ulceration (adjunct) | 6.6 mg/kg | PO | q8h | — |
| Gastric ulceration (IV) | 1.5–2 mg/kg | IV | q6–8h | — |

- 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

*Ranitidine doses for rabbits*

| Indication | Dose | Route | Frequency | Duration |
| --- | --- | --- | --- | --- |
| Suspected gastric ulceration | 2–5 mg/kg | PO | q12h | — |

- 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

*Ranitidine doses for primates*

| Indication | Dose | Route | Frequency | Duration |
| --- | --- | --- | --- | --- |
| Gastric / duodenal ulcer (monkeys) | 0.5 mg/kg | PO | q12h | — |

- 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

> **Caution:** 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

> **Caution:** 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

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- [Misoprostol](https://vetmasterji.com/drugs/misoprostol)
- [Omeprazole](https://vetmasterji.com/drugs/omeprazole)
- [Pantoprazole](https://vetmasterji.com/drugs/pantoprazole)
- [S-Adenosylmethionine (SAMe)](https://vetmasterji.com/drugs/sam-e)
- [Silymarin (Milk Thistle / Silybin)](https://vetmasterji.com/drugs/silymarin)
- [Sucralfate](https://vetmasterji.com/drugs/sucralfate)
- [Sulfasalazine](https://vetmasterji.com/drugs/sulfasalazine)

## Frequently asked questions

### What is the dose of Ranitidine for dogs?

Reference doses for Ranitidine in dogs: 1–2 mg/kg PO q8–12h (Acid suppression / ulcer / prokinetic). Confirm against the label and the patient before use.

### What is the dose of Ranitidine for cats?

Reference doses for Ranitidine in cats: 1–3.5 mg/kg PO q12h (Acid suppression / gastritis). Confirm against the label and the patient before use.

### What is the dose of Ranitidine for horses?

Reference doses for Ranitidine in horses: 6.6 mg/kg PO q8h (Gastric ulceration (adjunct)); 1.5–2 mg/kg IV q6–8h (Gastric ulceration (IV)). Confirm against the label and the patient before use.

### When should Ranitidine not be used?

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.

### What are the side effects of Ranitidine in animals?

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

## Sources

- Plumb's Veterinary Drug Handbook
- Merck Veterinary Manual, 11th edition
- Papich, Papich Handbook of Veterinary Drugs, 5th edition
- Carpenter, Exotic Animal Formulary

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VetMasterJi is a clinical decision-support and education platform for veterinary professionals and students. It does not provide veterinary advice, diagnosis or treatment for specific animals. All drug doses, calculators and differentials are references that must be independently verified before clinical use; the attending registered veterinarian remains solely responsible for every clinical decision.