About cimetidine
Histamine-2 receptor blocker
Used for
- Short-term relief of heartburn and acid indigestion
- Treatment of stomach or duodenal ulcers
- Treatment of gastro-oesophageal reflux disease
- Treatment of excess stomach acid, including Zollinger–Ellison syndrome
Usual adult dose
Heartburn: 200 mg up to four times daily. Ulcers or reflux: commonly 400 mg twice daily or 800 mg at bedtime; prescribed doses vary.
Usual dose in children
Specialist-directed: commonly 20–40 mg/kg daily in divided doses; maximum depends on age and condition.
Common side effects
- Headache
- Diarrhoea or constipation
- Dizziness
- Confusion, especially in older adults or people with kidney problems
Important warnings
- Dose reduction may be needed with kidney impairment.
- Rarely causes blood-cell problems or liver inflammation.
- Long-term use may contribute to vitamin B12 deficiency.
- Persistent or severe symptoms need medical assessment.
Pregnancy
Use only when clinically needed; pregnancy safety data are limited.
Breastfeeding
Small amounts enter breast milk; use only when needed and with professional guidance.
Interactions
- Can raise levels of warfarin, phenytoin, theophylline, and some sedatives.
- May reduce absorption of medicines needing stomach acid, such as ketoconazole.
- Antacids can reduce absorption; separate doses as directed.
AI-generated from general medical knowledge, not from this product's official leaflet. It may be incomplete or out of date. Not medical advice — ask a pharmacist or doctor before making any decision.