Sounds like 'eryth-ro-my-cin'

Key points about erythromycin

  • Erythromycin is an antibiotic used to treat different infections caused by bacteria.
  • Erythromycin is also called E-Mycin or ERA. 
  • Find out how to take it safely and possible side effects.
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Erythromycin is an antibiotic that is used to treat infections such as infections of the chest, mouth, skin, stomach and genitals. It works by killing or stopping the growth of bacteria (bugs). It is often used for people who are allergic to penicillins. Like all antibiotics, erythromycin is not effective against infections caused by viruses.

In New Zealand, erythromycin is available as tablets (400 mg, 250 mg and 500 mg) and liquid and can be given as an injection in the hospital. 

  • The dose of erythromycin will be different for different people depending on the type of infection and your age.
  • Adults: the usual dose is one tablet two, three or four times a day.
  • Children: the dose for children will depend on their body weight. It is usually given 2 to 4 times a day.
  • Your doctor will advise you on how long to take erythromycin for (usually 5 to 10 days), but depending on the infection, it could be longer.
  • Always take your erythromycin 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. 

  • You can take erythromycin with or without food. If you get stomach upset try taking it with food
  • Tablets: swallow the tablet with a glass of water. Do not chew them.
  • Liquid: shake the medicine well. Measure the right amount using an oral syringe or medicine spoon. You can get these from your pharmacy. Do not use a kitchen spoon as it will not give you the right amount. Read more: Tips on how to give medicines to babies and children.
  • Timing: Try to space your doses evenly throughout the day.
    • Twice a day: this should be in the morning and in the evening.
    • Three times each day: this should be in the morning, early afternoon and at bedtime.
    • Four times each day: this should be about 4 hours apart, for example 7am, 11am, 3pm and 7pm.
  • Missed dose: If you forget to take your dose at the correct time, take one as soon as you remember. Try to take the correct number of doses each day. Do not take two doses at the same time to make up for a forgotten dose.
  • If you are sick: If you are sick (vomit) less than 30 minutes after having a dose of erythromycin, take the same dose again. But, if you are sick (vomit) and it is more than 30 minutes after having a dose of erythromycin, you do not need to take another dose. Wait until the next dose. If you are vomiting and are worried, contact your doctor or Healthline (0800 611 116) for advice.
  • Alcohol: Alcohol may slow down or delay the medicine working. It's best to stop drinking alcohol or limit how much you drink while you're taking erythromycin.

Other tips

  • Store your tablets in a cool, dry place, away from direct heat and light. If you have been given liquid medicine, this will have been made up by the pharmacy and you may need to keep it in the fridge - check the instructions on the bottle. Make sure the medicine does not freeze.
  • It is best to 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.

  • Do you have problems with your kidneys or liver?
  • Do you have problems with your heart, especially changes in your heart rate?
  • Do you have myasthenia gravis (causes tired and weak muscles)?
  • Are taking any other medicines? This includes any medicines you are taking which you can buy without a prescription, as well as herbal and complementary medicines.

If so, it’s important that you tell your doctor or pharmacist before you start erythromycin. Sometimes a medicine isn’t suitable for a person with certain conditions, or it can only be used with extra care.

Like all medicines, erythromycin 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 erythromycin with or after food.
  • Tell your doctor if you are worried.
  • Diarrhoea (runny poos)
  • These may go away with time.
  • Tell your doctor if troublesome.
  • Vaginal itching, soreness or discharge (thrush)
  • Tell your doctor or pharmacist.
  • Changes in your heartbeat (fast or irregular)
  • 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, pain in the abdomen. 
  • Tell your doctor immediately or ring HealthLine 0800 611 116
  • Signs of an allergic reaction such as skin rash, itching, swelling of the lips, face, and mouth or difficulty breathing
  • Tell your doctor immediately or ring HealthLine 0800 611 116
Did you know that you can report a side effect to a medicine to CARM (Centre for Adverse Reactions Monitoring)? Report a side effect to a product(external link)

Erythromycin may interact with a few medications or herbal supplements, so check with your doctor or pharmacist before starting erythromycin or before starting any new medicines. If you are taking the contraceptive 'pill', the effectiveness of the 'pill' can be reduced if you have a bout of being sick (vomiting) or diarrhoea which lasts for more than 24 hours. If this happens, ask your doctor or pharmacist for advice about contraception over the following few days.

Medsafe Consumer Information Sheet E-Mycin(external link)
New Zealand Formulary Patient Information: Erythromycin(external link) (te reo Māori(external link)My Medicines, NZ, 2019


Erythromycin paediatric dose calculator


  1. Erythromycin(external link) New Zealand Formulary
  2. Erythromycin(external link) New Zealand Formulary for Children

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

Reviewed by: Angela Lambie, Pharmacist, Auckland

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