Home
Bupa members

Support and offers for individual members and customers

Antibiotics

Published by Bupa's health information team, May 2009.

This factsheet is for people who are taking antibiotics, or who would like information about them.

Antibiotics are used to treat infections caused by bacteria. The very first antibiotic discovered was penicillin, and it's still widely used to treat many common infections. In the UK, antibiotics are only available on prescription from a doctor, a nurse prescriber or a dentist.

Why would I take antibiotics?

You may take an antibiotic to treat an infection that's caused by bacteria.

Common illnesses caused by bacteria include impetigo (a skin infection), tonsillitis (inflammation of the tonsils), pneumonia, salmonella (food poisoning) and many sexually transmitted diseases. Many infectious illnesses aren't caused by bacteria but by viruses or other micro-organisms. Viruses can cause flu, measles, mumps and hepatitis, for example.

Antibiotics aren't effective against viruses but can treat bacterial infections.

If you're having an operation, you may be given antibiotics to prevent an infection. This is known as 'prophylaxis' and is particularly common before surgery for repairing broken bones and joints, and before bowel surgery.

What are the main types of antibiotics?

Some antibiotics can be used to treat a wide range of bacterial infections and are known as broad-spectrum antibiotics. Examples include amoxicillin and cefotaxime. Other antibiotics are only effective against specific types of bacteria and are known as narrow-spectrum antibiotics. Examples include vancomycin and teicoplanin.

Some antibiotics work against bacteria that need oxygen to live ('aerobic' bacteria), such as those that can infect the skin. Other antibiotics work against bacteria that don't need oxygen and can multiply inside the body where there is no oxygen available ('anaerobic' bacteria).

How do antibiotics work?

Some antibiotics, such as penicillin, are bactericidal. This means that they kill bacteria. They usually do this by interrupting the chemical processes that the bacteria use to make their cell walls.

Other antibiotics, such as erythromycin, are described as bacteriostatic. This means that they work by stopping bacteria from growing and multiplying. Most bacteria don't live long, so the colony of bacteria eventually dies out.

How to take antibiotics

Antibiotics are given for a specific period of time - usually seven to 10 days - and you will need to take them at regular, specified intervals (every four, six, eight or 12 hours). This is necessary to keep the right amount of medicine in your bloodstream - too much could cause you to have more side-effects, but too little might not be completely effective against your infection.

Some antibiotics have specific instructions about taking them before, after, or during meals. You shouldn't take some antibiotics with certain foods and drinks. Others are best taken when there is no food in your stomach, usually an hour before meals or two hours afterwards. So it's important to read and carefully follow the instructions that come with your medicine.

You shouldn't drink any alcohol if you're taking the antibiotic metronidazole (Flagyl), as it can make you feel very sick. Don't take tetracycline antibiotics with milk as this can reduce the absorption of this type of antibiotic. Make sure you follow the instructions on the medicine label or patient information leaflet, and if you have any questions ask your doctor or pharmacist for advice.

If you don't take your antibiotics according to the instructions given, this can lead to bacteria becoming resistant to them. Bacteria can develop inherited mutations which can make them resistant to a particular antibiotic or to different types of antibiotic. These bacteria can then become difficult to treat. Stopping taking antibiotics too early may also increase the risk of antibiotic resistance. Resistance can lead to further, and possibly more serious, infections.

It's important to take antibiotics only when it's really necessary. Always take them as directed by your doctor and don't stop taking them early, even if your symptoms improve.

Antibiotics usually come as tablets or capsules (or syrup for children). They can also be given by injection, or applied to the affected part of your body such as the skin, eyes or ears as drops, lotions or ointments.

Special care

You should speak to your doctor before taking antibiotics if you know you have problems with your liver or kidneys.

Before taking antibiotics, tell your doctor or pharmacist if you're pregnant, breastfeeding, or if you're taking any other medicines or the contraceptive pill.

Side-effects of antibiotics

Side-effects are the unwanted, but mostly mild and temporary effects of a successful treatment. The most common side-effects with antibiotics are diarrhoea, feeling sick and vomiting. However, you might not have any obvious side-effects.

After treatment with broad-spectrum antibiotics, you might get a fungal infection such as thrush. This is because antibiotics may destroy your body's harmless bacteria that help to control overgrowth of micro-organisms like fungi, as well as the harmful bacteria responsible for the infection you're being treated for.

Rare, but more serious side-effects of antibiotics can occur in some people. These include kidney problems, problems with blood clotting, increased sensitivity to the sun, blood disorders and deafness.

Allergies

Some people are allergic to antibiotics, particularly penicillin and similar medicines such as cephalosporins. If you're allergic to antibiotics, you may get side-effects such as a rash, swelling of the face and tongue, and difficulty breathing. This is called an 'anaphylactic' reaction and it can be serious or even fatal. As an alternative to penicillin, doctors may prescribe erythromycin, which works against the same types of bacteria.

Some people think they have had an allergic reaction, when really it was a side-effect. Always tell your doctor or pharmacist if you think you have had an allergic reaction to an antibiotic before.

Interactions of antibiotics with other medicines

Certain antibiotics (penicillins, cephalosporins and others) can stop the contraceptive pill from working properly. If you have diarrhoea or vomiting while taking an antibiotic, your contraceptive pill might not be properly absorbed into your body. If you experience either while you're taking antibiotics, you should use additional (ie barrier) contraception.

There are a number of important interactions between antibiotics and other medicines. So it's important to check with your doctor or pharmacist before you take any other medicines or herbal remedies at the same time as taking antibiotics.

Resistance

Some infections are resistant to certain antibiotics. For example, meticillin-resistant Staphylococcus aureus (MRSA) can't be treated with standard antibiotics.

Resistance can start when bacteria causing an infection aren't completely killed off by the antibiotic used. Some bacteria survive because they have an inherited mutation. The few bacteria that survive are then able to cause an infection that is resistant to treatment with that particular antibiotic. It's a form of natural selection for bacteria (survival and successful reproduction of the organisms that are best suited to their environment).

Names of common antibiotics

Examples of the main types of antibiotics are shown in the table.

You may have noticed that your medicine has two or more names. All medicines have a generic name, which is its official medical name. Many medicines also have at least one brand name, which is the trade name. Generic names are written in lower case and brand names start with a capital letter.

Generic names Examples of common brand names

Penicillins

amoxicillin

Amoxil

ampicillin

Penbritin

benzylpenicillin

Penicillin G

co-amoxiclav

Augmentin

flucloxacillin

Floxapen

phenoxymethylpenicillin

Penicillin V

Macrolides

clarithromycin

Klaricid

erythromycin

Erymax, Erythrocin, Erythroped

Cephalosporins

cefaclor

Distaclor

cefalexin

Ceporex, Keflex

cefotaxime

Claforan

Tetracyclines

doxycycline

Vibramycin

oxytetracycline

Oxymycin

tetracycline

 

Aminoglycosides

gentamicin

Cidomycin

neomycin

Nivemycin

Quinolones

ciprofloxacin

Ciproxin

Others

chloramphenicol (eye drops for conjunctivitis)

 

clindamycin

Dalacin C

isoniazid (for treatment of tuberculosis)

 

metronidazole

Flagyl

rifampicin (for treatment of tuberculosis)

 

trimethoprim

Trimopan

vancomycin

Vancocin

Related topics

Further information

Sources

  • Joint Formulary Committee, British National Formulary. 54th ed. London: British Medical Association and Royal Pharmaceutical Society of Great Britain, 2008: 274-318
  • Dental aspects of endocarditis prophylaxis: new recommendations from a working group of the British Cardiac Society Clinical Practice Committee and Royal College of Physicians Clinical Effectiveness and Evaluation Unit. Royal College of Surgeons of England. 2004. wwww.rcseng.ac.uk
  • Warrell DA, Cox TM, Firth JD. Oxford Textbook of Medicine. 4th ed. Vol 1. Oxford: Oxford University Press, 2005:296-297
  • Vaginal infections: thrush and bacterial vaginosis. Family Planning Association. 2006. www.fpa.org.uk
  • Longmore M, Wilkinson IB, Rajagopalan S. Oxford Handbook of Clinical Medicine. 6th ed. Oxford: Oxford University Press, 2004:543

This information was published by Bupa's health information team and is based on reputable sources of medical evidence. It has been peer reviewed by Bupa doctors. The content is intended for general information only and does not replace the need for personal advice from a qualified health professional.

Publication date: May 2009

 

Rate this page

Feedback

Have you found the information in this factsheet helpful? Do take a couple of moments to give us your feedback.

Click here to give us your feedback

Up to £100 off a Bupa Health assessment

Bupa health insurance

Free online health check

Bupa Care Homes

Bupa travel cover