How does clarithromycin work?
Clarithromycin is one of a group of medicines called macrolide antibiotics. They work by killing the bacteria causing the infection.
When will I feel better?
For most infections, you should feel better within a few days.
For skin problems such as cellulitis, you may have to take the medicine for about 7 days before you see any improvement.
If you have a Helicobacter pylori infection, even if the bacteria are no longer in your stomach, it can take some time before you feel better.
Your doctor will usually give you a medicine to reduce stomach acid, such as omeprazole or lansoprazole, while the ulcer heals. You should start feeling better when you finish the treatment to reduce your stomach acid.
It's very important to keep taking clarithromycin until your course is finished. Do this even if you feel better. It'll help to stop the infection coming back.
What if I do not get better?
Tell your doctor if you do not start feeling better after taking clarithromycin for:
- 3 days for a chest infection
- 7 days for cellulitis
Also tell them if, at any time, you start to feel worse.
If you have a Helicobacter pylori infection, your doctor will arrange a follow-up test 6 to 8 weeks after you started clarithromycin. They'll also usually give you a medicine to reduce stomach acid, such as omeprazole or lansoprazole.
If your symptoms do not get better in that time or you notice any new problems, like losing weight, contact your doctor as soon as possible.
How does clarithromycin compare with other antibiotics?
There are other macrolide antibiotics that work in the same way as clarithromycin. They include azithromycin and erythromycin.
It's usual to take clarithromycin twice a day, but for azithromycin it's once a day, and for erythromycin it's usually 4 times a day.
Clarithromycin and azithromycin are less likely to cause diarrhoea than erythromycin.
Most macrolides can be used to treat chest and skin infections. But azithromycin and erythromycin can also be used to treat sexually transmitted infections.
Clarithromycin can also be used to treat Helicobacter pylori, a bacteria that can cause stomach ulcers.
Clarithromycin and other macrolide antibiotics kill similar types of bacteria to penicillin antibiotics, such as amoxicillin.
If you are allergic to penicillin antibiotics you can take clarithromycin instead.
Will it give me thrush?
Some people get a fungal infection called thrush after taking a course of antibiotics like clarithromycin. This is 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?
Clarithromycin does not stop any type of contraception from working, including the combined pill or emergency contraception.
But if clarithromycin makes you vomit or have severe diarrhoea for more than 24 hours, your contraceptive pills may not protect you from pregnancy. Check the pill packet to find out what to do.
Find out more:
Can I drink alcohol while taking clarithromycin?
Yes, you can drink alcohol with clarithromycin.
Is there any food or drink I need to avoid?
You can eat and drink normally while taking clarithromycin.