Family doctor



AMOXYCILLIN - a patient's guide


Amoxycillin is a penicillin that is used to treat a wide range of infections. This article profiles the medication, its uses, and side effects.



Amoxil, Penamox, Moxlin

Contains Amoxycillin. Available in capsules, syrups and sachets.

USE: Infections caused by bacteria that are affected by amoxycillin

Amoxycillin is a commonly used penicillin that works against a wide range of bacteria. It is in the group called beta-lactams. Amoxycillin (and the others in the beta-lactam group) works by stopping the making of the cell wall of susceptible bacteria, causing the bacteria to die. Some bacteria are not susceptible to amoxycillin, but they might be susceptible to other penicillins, or other antibacterials. Your doctor will sometimes swab the area of infection to see which is the best antibacterial to give.

Penicillins do not work against viruses or fungi so, for example, would not be any use against a cold, the flu or athlete's foot. However, sometimes an illness that might initially be caused by a virus or fungi may then be complicated by bacteria making the most of your defences being down. This is why sometimes a cold may develop into a chest or sinus infection that needs penicillin or another antibacterial to cure it.

Some bacteria have developed themselves to become resistant to amoxycillin and some other antibacterials; this is a big problem.

You can help against the problem of resistance by following these guidelines:

  • Do not use these medicines for uncomplicated colds and flus (unless your doctor thinks bacteria may be involved)
  • Do not share your medicine with other people
  • Take the full course you have been prescribed even if you are starting to feel better (unless your doctor tells you to stop early)
  • Do not keep any left-over penicillin in the cupboard to treat yourself later - talk to your doctor or pharmacist first

Amoxycillin can be used for:

  • Bacterial infections of the airways (e.g. a chest or sinus infection)
  • Middle ear infections
  • Prevention of endocarditis in dentistry
  • Uncomplicated urinary tract infections
  • Some skin and soft tissue infections

It depends on which bacteria are thought to be causing the infection as to whether amoxycillin is used or not. An infection caused by bacteria that is not affected by amoxycillin should be treated with another antibacterial.


  • It is very important that people who are allergic to penicillins or cephalosporins are not given amoxycillin.
  • Amoxycillin should not be used in glandular fever (infectious mononucleosis).
  • The dose needs to be adjusted if kidneys are not working to full capacity.
  • Sodium benzoate is in the liquid forms and the sachet.

Side effects:

There are very many people treated every day with amoxycillin and very few will notice any side effects. The more common side effects are mild and only last a short time.

  • The most serious side effect is allergy, which can include swelling of the face and throat, itching and skin rash and difficulty breathing. This side effect is very rare, and a doctor must be seen immediately. People who are allergic to penicillin should get a Medic Alert bracelet to warn doctors not to give penicillin or related medicines.
  • A mild skin rash and itching can occur, and rarely other skin problems can happen - check with a doctor if you have any skin problems with this medicine.
  • Rarely an effect on the kidneys, liver or blood can occur.
  • Nausea, vomiting and diarrhoea can sometimes happen.
  • Rarely dizziness, increased muscle activity and convulsions have been reported.
  • Longer use of amoxycillin can sometimes change the normal balance of "bugs" in the body. This can mean that women can get vaginal thrush, or babies can get a fungal nappy rash or thrush in the mouth (look for white spots in the mouth). Talk to your doctor or pharmacist if affected.

There may be other side effects, so if you have any unexpected symptoms while taking this medicine, tell your doctor or pharmacist.


  • One very important interaction is that amoxycillin can make the oral contraceptive ("the pill") less effective. Therefore, other precautions, e.g. condoms, should be used to prevent pregnancy. Talk to your doctor or pharmacist about how long you need to use other precautions.
  • Probenecid can increase the amount of amoxycillin in the body.
  • Allopurinol can increase the possibility of skin problems.
  • Some other medicines working against bacteria (e.g. tetracyclines) can interfere with the bacterial effects of amoxycillin.
  • Tests for glucose in the urine can be affected by amoxycillin.

Patient information:

  • Follow the instructions on the label of the medicine or as directed by your doctor.
  • Keep all medicines out of the reach of children.
  • Finish the course of antibiotic even if you are starting to feel better (unless your doctor says to stop early).
  • If you are not starting to feel any better after taking the medicine for a few days, or if you are feeling worse, talk to your doctor.
  • If you have any swelling of the face, tongue, mouth or throat, talk to a doctor immediately - do not delay. Tell the doctor you are taking penicillin.
  • If you are taking "the pill" remember that amoxycillin may stop the pill from working - use other methods of contraception while taking and for a time after stopping the course of amoxycillin (talk to your doctor or pharmacist about this).
  • Do not share your medicine with anyone else, even if they have the same symptoms as you do.
  • Do not start yourself on a left-over medicine - always see your doctor first.
  • Syrups or suspensions are usually best kept in the refrigerator, and they only last about 14 days usually, so any left-overs will need to be thrown out. Shake the syrup before using, and use an accurate measure (not just a teaspoon).

See also:

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