How does metronidazole work?
Metronidazole is an antibiotic. It works by stopping the growth of the bacteria or parasites causing the infection.
When will I feel better?
For most infections, you should feel better within a few days. With serious swelling, including dental infections, the medicine will start working within a few days but it may take longer before your symptoms start to get better.
For some of the infections that metronidazole is used for, you may only begin to notice an improvement after a week.
When using the cream or gel to treat rosacea, you may have to wait a few weeks before you see any improvement.
It's very important that you keep taking metronidazole until you finish the course. Do this even if you feel better. It will help stop the infection coming back.
What if I do not get better?
Tell your doctor if you still do not feel better 2 or 3 days after finishing your course of metronidazole. Also tell them if you start to feel worse at any time.
Will it give me thrush?
Some people get a fungal infection called thrush after taking a course of antibiotics like metronidazole. This is more common if you're using the vaginal gel. It happens because antibiotics kill the normal harmless bacteria that help to protect you against thrush.
Ask your pharmacist or doctor for advice if this happens to you.
Will it affect my contraception?
Metronidazole does not stop any type of contraception from working, including the combined pill and emergency contraception.
However, if metronidazole makes you vomit or have severe diarrhoea for more than 24 hours, your contraceptive pills may not protect you from pregnancy. If this happens, follow the instructions in the leaflet that comes with your contraceptive pills.
Find out more about what to do if you're on the pill and you're being sick or have diarrhoea.
Can I drive or ride a bike?
Metronidazole does not usually affect you being able to drive or cycle.
However, very rarely, some people suffer from drowsiness or blurred vision. If this happens to you, do not drive, ride a bike or operate heavy machinery until you stop feeling drowsy and you can see clearly.
It's an offence to drive a car if your ability to drive safely is affected. It's your responsibility to decide if it's safe to drive. If you're in any doubt, do not drive.
GOV.UK has more information on the law on drugs and driving.
Can I drink alcohol while taking metronidazole?
Do not drink alcohol while you're taking metronidazole, including the 2 days after you finish. This gives the medicine time to leave your body.
This is important because metronidazole can react with alcohol to cause a number of side effects. These include feeling and being sick, stomach pain, hot flushes, a pounding heartbeat (palpitations) and a headache.
Is there any food or drink I need to avoid?
You must not have any alcohol (in either your food or drink) while taking metronidazole, and for 2 days afterwards.
Otherwise you can eat and drink normally.