Metronidazole

What is metronidazole used for?

Metronidazole is an antimicrobial medicine which is used to treat a wide range of infections, with high activity against anaerobic bacteria and protozoa. It is available in various forms, including tablets, capsules, oral suspensions, creams, gels, suppositories and infusions[1][2]. 

Metronidazole is commonly prescribed for[2]: 

• Bacterial vaginosis 

• Pelvic inflammatory disease 

• Dental infections 

• Skin infections (e.g., rosacea) 

• Other suscepitble infections such as trichomoniasis, H. Pylori or Amoebiasis  

• Surgical prophylaxis

How does metronidazole work?

Metronidazole is thought to work by entering the cells of microorganisms and disrupting their DNA, which prevents them from multiplying and ultimately kills them. It is particularly effective against anaerobic bacteria (bacteria that don’t need oxygen to survive) and protozoa[2]. 

Who can take metronidazole?

Most adults and children can take metronidazole, but talk to your doctors before taking if [1][2]: 

• You have or have ever had liver problems or disease 

• You have had an allergic reaction to metronidazole, nitroimidazoles, or other ingredients listed as part of your medicine 

• You are having dialysis 

• You are pregnant or breastfeeding women (only under medical advice) 

• You have a history of a disease of the nervous system 

Please tell your doctor or pharmacist about any conditions you may have before starting metronidazole, and always follow the instructions in the Patient Information Leaflet[1]. 

How do you take metronidazole?

Metronidazole tablets should be swallowed whole with a glass of water with or after food to reduce stomach upset[1][2].   

Metronidazole oral suspension does not need to be taken after food. If you take the liquid form, it should come with a syringe or spoon designed to hold the correct amount. If you do not have either, ask your pharmacist rather than using a kitchen teaspoon. 

Doses of metronidazole should be spaced out evenly during the day. 

Do not drink alcohol during treatment and for at least 48 hours after finishing, as it can cause severe reactions. You must complete the full course even if you feel better or the infection could return. 

Topical creams and gels are usually applied thinly twice a day. 

What is the usual dosage of metronidazole?

The dose depends on the condition being treated, how serious it is, and whether it is tablets, liquid, creams, gels, or suppositories[2]. 

Some infections are treated with a single dose and others with a 2-week course. Children’s doses depend on the age and weight of the child. 

It is very important to follow the instructions of the doctor or pharmacist provided for your medicine. 

Can you stop taking metronidazole early?

No. You must always complete the course even if you feel better. Stopping early can lead to the infection returning or becoming resistant. Always finish the prescribed course unless advised otherwise by a healthcare provider[2]. 

What do you do if you take too much metronidazole?

Taking an extra dose will unlikely be harmful. Speak to your pharmacist or doctor if you have taken more than 1 extra dose or if you are worried[2]. 

What do you do if you forget to take metronidazole?

If you miss a dose, take it as soon as you remember. If it's almost time for your next dose, skip the missed dose and continue with your regular schedule. Never take 2 doses at the same time[2]. 

What are the side effects of metronidazole?

Side effects may occur with tablets, liquids, suppositories, or vaginal gel, but it's rarer with topical metronidazole cream or gel[1]. 

The most common side effects of metronidazole include[2]: 

• Nausea 

• Metallic taste 

• Headache 

• Diarrhoea 

More serious rare side effects (contact 111 or GP for advice) include[2]: 

• Seizures 

• Pains in the muscles or joints 

• Severe skin rash 

• Signs of liver problems (yellowing of skin/eyes) 

If you are experiencing any of these more serious side effects, consult your doctor or visit A&E immediately. 

If you experience any side effects, including those not listed, you are encouraged to report them via the Yellow Card Scheme or contact your doctor, pharmacist, or nurse. This information is intended as a summary for general awareness and does not replace professional medical advice.

The information provided in the side effects section is not a comprehensive list of all possible side effects associated with this medication. For a complete list of side effects, please refer to the Patient Information Leaflet (PIL) provided with your medication or consult your healthcare professional[1]. 

Medicines you can and can't take with metronidazole

This does not refer to topical metronidazole cream or gel. 

Avoid or use with caution[2]: 

• Avoid Alcohol whilst on treatment (causes severe nausea, vomiting, cramps) 

• Warfarin (increased bleeding risk) 

• Lithium (risk of increased lithium concentration and toxicity) 

• Phenytoin or phenobarbital (may reduce effectiveness of metronidazole and increase risk of peripheral neuropathy) 

• Disulfiram (can cause acute psychotic reactions) 

• Fluorouracil (increased toxicity) 

Always inform your doctor or pharmacist about all medications and supplements you take before you start a new medicine, and follow the instructions in the Patient Information Leaflet[1]. 

Frequently asked questions about metronidazole

Can I drink alcohol while taking metronidazole? 

No. Do not drink alcohol whilst you’re taking metronidazole and for 2 days afterwards. It can cause severe reactions like nausea, vomiting, and flushing[2]. 

Can I take it during pregnancy? 

Yes, metronidazole can be prescribed during pregnancy[2]. 

Can I drive while taking metronidazole? 

Yes, you can, unless you feel dizzy or confused[2]. 

Is it safe for children? 

Yes, metronidazole is safe for children[2].

For the official NHS guide to metronidazole, visit their website.