Ampicillin for infections

Make sure you tell your doctor if you are allergic to penicillin. Ampicillin is a type of penicillin - do not take it if you are allergic to penicillin.

Space your doses out evenly over the day and complete the full course of this antibiotic, even if you feel your infection has cleared up. You should take ampicillin an hour before food.

If you have an allergic reaction (such as any swelling around your mouth, any difficulties breathing or a red rash) contact a doctor straightaway.

Type of medicine Penicillin antibiotic
Used for Infections (in adults and children)
Also called Penbritin®
Available as Capsules, oral liquid and injection

Ampicillin is used for bacterial infections, such as some respiratory infections, urine infections and ear infections. It works by killing the bacteria causing the infection.

Some medicines are not suitable for people with certain conditions, and sometimes a medicine may only be used if extra care is taken. For these reasons, before you start taking ampicillin it is important that your doctor or pharmacist knows:

  • If you are pregnant or breast-feeding.
  • If you think you have glandular fever.
  • If you have kidney problems.
  • If you are taking any other medicines. This includes any medicines you are taking which are available to buy without a prescription, such as herbal and complementary medicines.
  • If you have an allergic condition, or if you have ever had an allergic reaction to a medicine. This is particularly important if you have ever had a bad reaction to any penicillin antibiotic.
  • Before you start this antibiotic, read the manufacturer's printed information leaflet from inside the pack. The leaflet will give you more information about it and and a full list of side-effects which you may experience from taking it.
  • Take ampicillin exactly as your doctor tells you to. It is usually taken four times daily, although a single dose may be prescribed for some infections.Your doctor or pharmacist will tell you how much to take and when to take it, and your dose will also be on the label of the pack to remind you. Space the doses out evenly during the day.
  • You should take ampicillin 'on an empty stomach', which means you should take it about an hour before a meal, or wait until two hours afterwards. This is because your body absorbs less ampicillin after a meal, which means the medicine is less effective.
  • Even if you feel your infection has cleared up, keep taking this antibiotic until the course is finished, unless you are told to stop.This is to prevent the infection from coming back. A course of treatment with this antibiotic does not usually last for longer than 7-14 days. If you still feel unwell after finishing the course, go back to see your doctor.
  • If you forget to take a dose, take one as soon as you remember. Try to take the correct number of doses each day, but do not take two doses at the same time to make up.
  • Some people develop thrush (redness and itchiness in the mouth or vagina) after taking a course of antibiotics. If this happens to you, speak with your doctor or pharmacist for advice.
  • If you are using combined oral hormonal contraception (the 'pill'), additional contraceptive precautions such as condoms are not required during a course of this antibiotic unless you are sick or have diarrhoea. If you need further advice about this, speak with your doctor or pharmacist.
  • This antibiotic may stop the oral typhoid vaccine from working. If you are having any vaccinations, make sure the person treating you knows that you are taking this medicine.

Along with their useful effects, most medicines can cause unwanted side-effects although not everyone experiences them. These usually improve as your body adjusts to the new medicine, but speak with your doctor or pharmacist if any of the following side-effects continue or become troublesome.

Common ampicillin side-effects - these affect less than 1 in 10 people who take this medicine What can I do if I experience this?
Feeling or being sick Stick to simple foods
Diarrhoea Drink plenty of water to replace any lost fluids. If the diarrhoea continues, becomes severe, or contains blood, let your doctor know straightaway
Skin rash Let your doctor know as soon as possible as your treatment may need to be changed

Important: if you develop an itchy rash, swollen face or mouth, or have difficulty breathing, these may be signs that you are allergic to a penicillin antibiotic. Do not take any more ampicillin and speak with your doctor or go to your local accident and emergency department straightaway.

If you experience any other symptoms which you think may be due to this medicine, speak with your doctor or pharmacist.

  • Keep all medicines out of the reach and sight of children.
  • Store in a cool, dry place, away from direct heat and light.
  • If you have been given liquid medicine, store it in a refrigerator. It will have been made up by the pharmacy and lasts for seven days, so check the expiry date on the bottle and do not use it after this date.

Never take more than the prescribed dose. If you suspect that you or someone else might have taken an overdose of this medicine, go to the accident and emergency department of your local hospital at once. Take the container with you, even if it is empty.

This medicine is for you. Never give it to other people even if their condition appears to be the same as yours.

If you buy any medicines, check with a pharmacist that they are safe to take with your other medicines.

If you are having an operation or any dental treatment, tell the person carrying out the treatment which medicines you are taking.

Do not keep out-of-date or unwanted medicines. Take them to your local pharmacy which will dispose of them for you.

If you have any questions about this medicine ask your pharmacist.

Further reading & references

Disclaimer: This article is for information only and should not be used for the diagnosis or treatment of medical conditions. EMIS has used all reasonable care in compiling the information but make no warranty as to its accuracy. Consult a doctor or other health care professional for diagnosis and treatment of medical conditions. For details see our conditions.

Original Author:
Helen Allen
Current Version:
Peer Reviewer:
Dr Adrian Bonsall
Document ID:
3604 (v24)
Last Checked:
17/01/2013
Next Review:
17/01/2016
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