Metronidazole and alcohol: why to avoid drinking during treatment

Metronidazole is an antibiotic. The NHS describes it as being used to treat infections including bacterial vaginosis, dental abscess, gum disease, pelvic inflammatory disease and, in cream or gel form, rosacea. It comes as tablets, liquid, skin gel, vaginal gel, skin cream and suppositories.

The NHS instruction on alcohol is among the clearest in its medicines guidance: do not drink alcohol while you are taking metronidazole tablets or liquid or using suppositories, and carry on avoiding it for 2 days after you finish. The reason given is that metronidazole can react with alcohol to cause a number of side effects, and the 2 days give the medicine time to leave your body.

That rule applies even to small amounts. A glass of wine or a beer is a reasonable thing to want, but the safer course is simply to wait, because the antibiotic course is usually short.

The NHS side-effects page says metronidazole can react with alcohol to cause side effects such as feeling or being sick, stomach pain, hot flushes, difficulty breathing and a pounding heartbeat. Its common questions page also lists headache. Some of these are unpleasant but short-lived; others, such as difficulty breathing, are more concerning.

If a reaction starts, stop drinking. The NHS says to stop drinking alcohol if symptoms appear after using the vaginal gel, and the same sensible step applies in other forms. If you are struggling to breathe, have chest pain or feel very unwell, call 999 or go to A&E. For milder but persistent symptoms, speak to a pharmacist or call NHS 111.

Most people think of drinks, but alcohol hides in other places. The NHS interaction page asks you to check with a pharmacist or doctor about any medicines you take as a liquid, in case these contain alcohol, and says some herbal remedies and supplements that come as liquids you drink may also contain alcohol. The label or the manufacturer can tell you.

• Any medicine you take as a liquid, which the NHS says may contain alcohol.

• Liquid herbal remedies and supplements, as the NHS notes.

• Ingredient lists and labels, or the supplier or manufacturer, which the NHS says can tell you whether a remedy contains alcohol.

The NHS draws a distinction. Tablets, liquid and suppositories carry the firm instruction. For vaginal gel, it says drinking alcohol can sometimes cause the same side effects, so you should stop drinking if they occur. For skin cream or gel, the NHS says the reaction is less likely because only a small amount is absorbed into the body.

The NHS vaginal gel course for bacterial vaginosis is typically one applicator every night for 5 nights, and the NHS also says not to have sex while using it. That is a short window in which to avoid alcohol if you want to be on the safe side.

The NHS stresses finishing the course even if you feel better, because stopping early could let the infection come back. That means the alcohol rule applies for the full course plus 2 days. If a special occasion falls inside the window, it is better to ask the prescriber or pharmacist about options than to skip doses.

Sources of support are available if cutting out alcohol is difficult for you. A GP or pharmacist can talk it through, and that conversation is worth having if alcohol dependence is a concern.

Alcohol is the best-known issue, but not the only one. The NHS lists warfarin, lithium, disulfiram, phenytoin or phenobarbitone, ciclosporin, and fluorouracil or busulfan among the medicines to check with a pharmacist or doctor. Tell whoever prescribes it about everything you take.

The NHS also lists rare but serious side effects, including yellowing of the eyes or skin, unexpected infections or bruising, severe stomach pain, and a headache with high temperature and stiff neck, which need medical attention. Stop taking metronidazole and call 999 or go to A&E if you develop headache, high temperature, stiff neck with sensitivity to light, or see or hear things that are not there, the NHS says.