Ranitidine Alternative (Cimetidine) — NZ Medication Guide
📋 Reviewed by a Registered Pharmacist NZ — This information is for general educational purposes only and does not replace professional medical advice. Always consult your doctor or pharmacist before starting, stopping, or changing any medication.
What is Ranitidine Alternative (Cimetidine)?
Cimetidine is an H2 receptor antagonist used for gastric acid suppression in peptic ulcer disease and GERD. This medication is funded by Pharmac but largely superseded by PPIs and famotidine.
What is Ranitidine Alternative (Cimetidine) Used For?
Cimetidine is used for peptic ulcer disease (gastric and duodenal ulcers), gastro-oesophageal reflux disease (GERD), and Zollinger-Ellison syndrome. It is less commonly used now due to significant drug interactions.
How Does Ranitidine Alternative (Cimetidine) Work?
Cimetidine competitively and reversibly blocks histamine H2 receptors on gastric parietal cells, reducing histamine-stimulated acid secretion. It also has a significant inhibitory effect on several CYP450 liver enzymes — a major source of drug interactions.
How to Take Ranitidine Alternative (Cimetidine)
200–400 mg twice daily or 400 mg at bedtime. Take with or without food. Dose reduction required in renal impairment. Onset of acid suppression within 1 hour, duration 6–8 hours.
Common Side Effects of Ranitidine Alternative (Cimetidine)
- Headache
- Dizziness
- Diarrhoea or constipation
- Fatigue
- Gynaecomastia (anti-androgenic effect — with prolonged use)
Serious Side Effects — Seek Medical Attention
Contact your doctor or call 111 immediately if you experience any of the following:
- Confusion and mental status changes (especially elderly patients and in renal impairment)
- Drug interactions — serious elevations of many medicines
- QT prolongation (rare)
- Hepatotoxicity (rare)
Drug Interactions
Ranitidine Alternative (Cimetidine) may interact with other medicines. Always inform your doctor and pharmacist of all medications you are taking. Key interactions include:
- MANY significant interactions (CYP450 inhibition): warfarin (markedly elevated INR), theophylline (toxicity), phenytoin (toxicity), metoprolol and other beta-blockers, tricyclic antidepressants, benzodiazepines, lidocaine
- Antacids (reduce cimetidine absorption — separate by 1–2 hours)
New Zealand Prescribing Information
Cimetidine (200 mg, 400 mg tablets) is funded by Pharmac but is infrequently prescribed in NZ due to its extensive drug interaction profile. Famotidine or a PPI are strongly preferred. Cimetidine’s anti-androgenic effects can cause gynaecomastia and decreased libido in men with prolonged use. If you take cimetidine, inform every prescriber and pharmacist — the interaction risk with other medicines is substantial.
Frequently Asked Questions
Why is cimetidine rarely used now?
Cimetidine inhibits multiple CYP450 liver enzymes, causing clinically significant elevations in the blood levels of many common medicines (warfarin, theophylline, phenytoin, many more). Safer H2 blockers (famotidine) and PPIs with fewer interactions are now preferred in clinical practice.
Does cimetidine affect male hormones?
Yes — cimetidine has weak anti-androgenic activity and can cause gynaecomastia (breast enlargement) and decreased libido in men with prolonged use. This effect is not seen with famotidine or PPIs and is another reason cimetidine has fallen out of favour.
References & Further Information
The following New Zealand and international resources were used to inform this page. We encourage you to consult these authoritative sources for the most current information:
- New Zealand Formulary — Cimetidine
- Pharmac — Funded Medicines Schedule
- Medsafe — Consumer Medicine Information
⚠️ Disclaimer: This page is for educational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your doctor or a qualified health provider. In New Zealand, medication availability and funding may vary — check with Pharmac or your pharmacist for current information.
Reviewed by a Registered Pharmacist NZ