Sounds like 'kla-RITH-roe-MYE-sin'

Key points about clarithromycin

  • Clarithromycin is an antibiotic used to treat infections caused by bacteria.
  • Clarithromycin is also called Apo-Clarithromycin® and Klacid®.
  • Find out how to take it safely and possible side effects.
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Clarithromycin is an antibiotic that is used to treat infections caused by bacteria. Examples of infections clarithromycin may be used for are Helicobacter pylori and community acquired pneumonia. 

It works by killing or stopping the growth of bacteria (bugs) that cause infection. Like all antibiotics, clarithromycin is not effective against infections caused by viruses.

In Aotearoa New Zealand clarithromycin is available as tablets, liquid and can be given as an injection in the hospital.

  • The usual adult dose is 500 mg twice a day. The dose may be lower if you have kidney problems.
  • The dose for children will depend on their body weight. It is usually given 2 times a day.
  • Your doctor will advise you on how long to take clarithromycin for (usually 7–14 days).
  • For most infections, you should feel better within a few days.
  • Always take your clarithromycin exactly as your doctor has told you. The pharmacy label on your medicine will tell you how much to take, how often to take it, and any special instructions. 

  • Timing of your doses: Take your doses at the same times each day. Try to space your doses evenly throughout the day – this should be in the morning and in the evening. You can take clarithromycin with or without food. Swallow the tablets with a drink of water.
  • Missed dose: If you forget to take your dose at the correct time, take it as soon as you remember. Try to take the correct number of doses each day. Do not take 2 doses at the same time to make up for a forgotten dose.
  • Finish the course: Take the whole course of antibiotics for the number of days your doctor has told you to. Do not stop taking it, even if you feel your infection has cleared up. If you stop your treatment early, your infection could come back.

Here are some things to know when you're taking clarithromycin. Other things may be important as well, so ask your healthcare provider what you should know about.

  • Clarithromycin does not have direct interactions with alcohol. This means that most people could have the occasional drink while taking it without any serious problems. However, if clarithromycin makes you feel sick (nausea), do not drink alcohol as it will make you feel worse.
  • If you are taking the contraceptive pill, you do not usually need to use additional contraception if you're taking clarithromycin. But if the antibiotic or the illness they're treating cause diarrhoea or vomiting, lasting more than 24 hours, absorption of the contraceptive pill may be affected. If this happens, ask your doctor or pharmacist for advice about contraception over the following few days.

Like all medicines, clarithromycin can cause side effects, although not everyone gets them. Often side effects improve as your body gets used to the new medicine.

Side effects What should I do?
  • Nausea (feeling sick) or vomiting
  • Take clarithromycin with or after food.
  • If you are sick (vomit) less than 30 minutes after having a dose of clarithromycin, take the same dose again. But, if you are sick (vomit) and it is more than 30 minutes after having a dose of clarithromycin, you do not need to take another dose. Wait until the next normal dose.
  • Tell your doctor if this bothers you.
  • Diarrhoea (runny poos)
  • Headache
  • This should settle after a few days.
  • Drink plenty of fluids such as water or squash to avoid dehydration.
  • Tell your doctor if these side effects bother you.
  • Vaginal itching, soreness or discharge (thrush)
  • Hearing loss, ringing in the ears
  • Tell your doctor or pharmacist.
  • Changes in your taste, sore mouth or dry mouth
  • Tell your doctor if this bothers you.
  • Signs of an allergic reaction such as skin rash, swelling of the face, lips, mouth or breathing problems
  • Tell your doctor immediately or ring Healthline 0800 611 116.
  • Signs of problems with your liver such as yellowing of the skin or eyes, dark urine, stomach pain, pale stools.
  • Stop taking clarithromycin. Tell your doctor immediately or ring Healthline 0800 611 116. 
For more information on side effects, see the Medsafe consumer information leaflets below. 

Did you know that you can report a medicine side effect to the Centre for Adverse Reactions Monitoring (CARM)? Report a side effect to a product.(external link)

The following links has more information about clarithromycin. 

Clarithromycin(external link) NZ Formulary, NZ
Klacid Medsafe(external link) Consumer Information, NZ


5 questions to ask about your medications(external link) Health Quality and Safety Commission, NZ, 2019 English(external link)te reo Māori(external link)


  1. Clarithromycin(external link) NZ Formulary, NZ
  2. Recommended regimens for Helicobacter pylori eradication in adults(external link) NZ Formulary, NZ
  3. Klacid(external link) Medsafe Product Datasheet, NZ
  4. Macrolides – don't upset the rhythm(external link) Medsafe Prescriber Update, NZ, 2015
  5. Antibiotics – choices for common infections(external link) BPAC, NZ, 2021

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Credits: Sandra Ponen, Pharmacist, Healthify He Puna Waiora. Healthify is brought to you by Health Navigator Charitable Trust.

Reviewed by: Maya Patel, Pharmacist, Auckland

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