Bio-Cimetidine contains cimetidine, an H2 blocker that reduces stomach acid. It is used for heartburn and acid reflux, indigestion, and stomach and duodenal ulcers. It comes as 200 mg and 400 mg tablets. Cimetidine interacts with a notably large number of other medicines, so check before combining it.
What is Bio Cimetidine?
Bio-Cimetidine is registered in South Africa as Schedule 3, obtained through a pharmacist:
| Product | Contains |
|---|---|
| Bio-Cimetidine 200 mg | Cimetidine 200 mg |
| Bio-Cimetidine 400 mg | Cimetidine 400 mg |
Cimetidine is an H2 receptor antagonist, usually shortened to “H2 blocker”. Histamine does more than cause allergic symptoms: acting on H2 receptors on the acid-producing cells of the stomach, it stimulates acid secretion. Cimetidine blocks those receptors, so less acid is produced.
H2 blockers sit between antacids and PPIs, and knowing where is genuinely useful:
- Antacids neutralise acid already in the stomach. They work within minutes but last only an hour or two.
- H2 blockers reduce acid production. They work within about an hour and last several hours — faster in onset than a PPI, though less powerful.
- Proton pump inhibitors such as omeprazole block acid production far more completely, but take a day or more to reach full effect.
That difference in timing has a practical use. An H2 blocker can be helpful for predictable evening or night-time symptoms, taken in advance — it acts sooner than a PPI while lasting longer than an antacid.
Cimetidine was the first H2 blocker, and it is the one now used least, because it inhibits liver enzymes that process a great many other medicines. Famotidine, a later H2 blocker, does not have this problem. If you take several regular medicines, this is worth raising — the interactions below are the main reason cimetidine has largely been superseded.
What is Bio Cimetidine commonly used for?
- Heartburn and acid reflux, including symptoms that recur at night.
- Indigestion (dyspepsia).
- Stomach (gastric) and duodenal ulcers, both healing and preventing recurrence.
- Reflux oesophagitis, where acid has inflamed the oesophageal lining.
- Protecting the stomach in some people taking anti-inflammatories.
- Zollinger-Ellison syndrome, a rare condition of acid overproduction.
It treats symptoms and helps ulcers heal, but does not address every cause. Ulcers are frequently caused by Helicobacter pylori infection or by anti-inflammatory medicines — and where H. pylori is present, acid reduction alone will not clear it. That needs antibiotics, and without them ulcers commonly return.
How Bio Cimetidine fits into this medicine category
| Group | Examples | Onset and strength |
|---|---|---|
| Antacids | Calcium/magnesium salts, Citro-Soda | Minutes; brief |
| Alginates | Gaviscon-type products | Minutes; form a barrier |
| H2 blockers | Cimetidine (Bio-Cimetidine), famotidine | About an hour; moderate, several hours |
| Proton pump inhibitors | Omeprazole, lansoprazole | A day or more; strongest and most sustained |
| Antispasmodics | Hyoscine | Gut cramping, not acid |
| Anti-nausea | Metoclopramide | Nausea and gastric emptying |
For healing an ulcer or significant oesophagitis, a PPI is generally preferred. See the digestive and stomach medicines hub.
What to check before using Bio Cimetidine
Check every other medicine you take with a pharmacist before starting. This is the most important point on this page. Cimetidine inhibits liver enzymes that metabolise many medicines, so their levels rise — sometimes to harmful concentrations.
Medicines particularly affected include:
- Warfarin — bleeding risk rises significantly.
- Phenytoin and carbamazepine for epilepsy.
- Theophylline for asthma.
- Some antidepressants, including tricyclics and SSRIs.
- Some benzodiazepines, increasing sedation.
- Certain heart medicines, including some beta-blockers and antiarrhythmics.
- Metformin.
- Ketoconazole and itraconazole, whose absorption falls when stomach acid is reduced.
- Clopidogrel, whose activation may be reduced.
Speak to a pharmacist or doctor first if you:
- Take any regular medicine — the list above is not exhaustive.
- Have kidney or liver disease, usually needing a lower dose.
- Are elderly, where confusion is more likely.
- Are pregnant or breastfeeding.
- Have difficulty swallowing, unintended weight loss, or are over 55 with new indigestion — these need assessment first.
Take it as directed, commonly with or after meals and at bedtime for night-time symptoms.
Possible cautions and when to ask a pharmacist or doctor
Common effects are diarrhoea, dizziness, tiredness, headache and rash.
Cimetidine has some hormonal effects other acid reducers do not, because it weakly blocks androgen receptors. With higher doses or prolonged use it can cause breast enlargement or tenderness in men (gynaecomastia), reduced sex drive, and erectile difficulty. These are reversible on stopping, and are a common reason for switching to a different medicine — worth mentioning rather than tolerating.
Seek medical advice if you develop:
- Confusion, agitation or hallucinations, particularly if elderly or if you have kidney or liver disease.
- A slow heartbeat, or palpitations.
- Yellowing of the eyes or skin.
- Fever, sore throat or mouth ulcers, or unusual bruising or bleeding — possible blood problems.
- Breast tenderness or swelling.
- A rash, blistering or peeling skin, or swelling of the face or lips.
- Muscle or joint pain.
See a doctor promptly, rather than self-treating, for:
- Vomiting blood, or vomit resembling coffee grounds.
- Black, tarry stools.
- Difficulty or pain on swallowing, or food sticking.
- Unintended weight loss.
- Persistent vomiting.
- A first episode of significant indigestion over 55.
- Symptoms persisting beyond two weeks of treatment, or recurring once you stop.
Chest pain is not always indigestion. Pain with breathlessness, sweating, or pain spreading to the arm or jaw needs emergency assessment.
Related medicine guides
Frequently asked questions
What is Bio-Cimetidine used for? Heartburn, acid reflux, indigestion, and stomach and duodenal ulcers. It contains cimetidine, an H2 blocker that reduces stomach acid.
What is Bio-Cimetidine 400 used for? The higher tablet strength, used for the same conditions — often for ulcer healing or more persistent symptoms.
How is it different from omeprazole? Cimetidine is an H2 blocker: it acts within about an hour but reduces acid less powerfully. Omeprazole is a PPI: stronger and longer-lasting, but takes a day or more to reach full effect.
How quickly does it work? Usually within about an hour, lasting several hours — faster than a PPI, slower than an antacid.
Can I take it with my other medicines? Check with a pharmacist first. Cimetidine interacts with an unusually large number of medicines, including warfarin, phenytoin and theophylline.
Can it cause breast enlargement in men? Yes, uncommonly, with higher doses or prolonged use, because it weakly blocks androgen receptors. It reverses on stopping — tell your doctor.
Can I take it with an antacid? Usually yes, though separating them by an hour or two is sensible. Ask a pharmacist.
How long can I take it? Short courses are usual for heartburn. Symptoms lasting beyond two weeks, or returning when you stop, need a doctor’s assessment.