Overview

Uses

Antibiotics are used to treat or prevent some types of bacterial infections. They're not effective against viral infections, such as the common cold or flu.

Antibiotics should only be prescribed to treat health problems:

• that are not serious but are unlikely to clear up without antibiotics – such as acne
• that are not serious but could spread to other people if not promptly treated – such as the skin infection impetigo or the sexually transmitted infection chlamydia
• where evidence suggests that antibiotics could significantly speed up recovery – such as a kidney infection
• that carry a risk of more serious complications – such as cellulitis or pneumonia

People at risk of bacterial infections

Antibiotics may also be recommended for people who are more vulnerable to the harmful effects of infection. This may include:

• people aged over 75 years
• babies less than 72 hours old who have a bacterial infection, or a higher than average risk of developing one
• people with heart failure
• people who have to take insulin for diabetes
• people with a weakened immune system – either because of an underlying health condition such as HIV or as a side effect of certain treatments, such as chemotherapy

Antibiotics to prevent infection

Antibiotics are sometimes given as a precaution to prevent, rather than treat, an infection. This is called antibiotic prophylaxis. Situations where antibiotics are given as a preventive treatment include:

• if you're having an operation
• after a bite or wound that could get infected
• if you have a health problem that means you're at higher risk of infection such as if you've had your spleen removed or you're having chemotherapy treatment

If you're having an operation

Antibiotics are normally recommended if you're having a type of surgery that carries a high risk of infection.

For example, you may be prescribed antibiotics if you're going to have:

• some types of eye surgery – such as cataract surgery or glaucoma surgery
• joint replacement surgery
• breast enlargement surgery
• pacemaker surgery
• surgery to remove the gall bladder
• surgery to remove the appendix

Your surgical team will be able to tell you if you need antibiotics

Bites or wounds

Antibiotics may be recommended for a wound that has a high chance of becoming infected – this could be an animal or human bite, for example, or a wound that has come into contact with soil or faeces.

Medical conditions

Some people are particularly vulnerable to infection, making antibiotics necessary. They include:

• people who have had their spleen removed
• people having chemotherapy for cancer
• people with sickle cell anaemia

In some cases, antibiotics are prescribed for people who have an infection that keeps coming back or that's causing distress or an increased risk of complications, such as: 

• cellulitis
• urinary tract infection
• genital herpes
• rheumatic fever

Side effects

Antibiotics can have side effects such as diarrhoea and feeling sick.

These side effects are usually mild and should pass once you finish your course of treatment.

If you get any additional side effects, contact your GP or the doctor in charge of your care for advice.

Antibiotic allergic reactions

Rarely, some people may have an allergic reaction to antibiotics, especially penicillin and cephalosporins.

In most cases, the allergic reaction is mild to moderate and can take the form of:

• a raised, itchy skin rash (urticaria, or hives)
• coughing
• wheezing
• tightness of the throat, which can cause breathing difficulties

These mild to moderate allergic reactions can usually be successfully treated by taking antihistamines.

But if you're concerned, or your symptoms do not get better with treatment, call your GP for advice. If you cannot contact your GP, call NHS 111 Wales.

In rare cases, an antibiotic can cause a severe and potentially life-threatening allergic reaction known as anaphylaxis.

Call 999 or go to A&E now if:

• you have a skin rash that may include itchy, red, swollen, blistered or peeling skin
• you're wheezing
• you have tightness in your chest or throat
• you have trouble breathing or talking
• your mouth, face, lips, tongue or throat start swelling

You could be having a serious allergic reaction and may need immediate treatment in hospital.

Tetracyclines and sensitivity to light 

Tetracyclines can make your skin sensitive to sunlight and artificial sources of light, such as sun lamps and sunbeds.

Avoid prolonged exposure to bright light while taking these medicines.

Fluoroquinolones

Severe aches and pains

In very rare cases, fluoroquinolone antibiotics can cause disabling, long-lasting or permanent side effects affecting the joints, muscles and nervous system.

Stop taking fluoroquinolone treatment straight away and see your GP if you get a serious side effect including:

• tendon, muscle or joint pain – usually in the knee, elbow or shoulder
• tingling, numbness or pins and needles

Heart problems

Fluoroquinolone antibiotics can cause serious side effects in people who are at risk of heart valve problems.

Stop taking fluoroquinolone treatment straight away and see your GP if you get a serious side effect including:

• swollen ankles, feet and legs (oedema)
• new heart palpitations (heartbeats that suddenly become more noticeable)
• sudden shortness of breath

Interactions

Antibiotics can sometimes interact with other medicines or substances. This means it can have an effect that is different to what you expected.

If you want to check that your medicines are safe to take with your antibiotics, ask your GP or local pharmacist.

Some antibiotics need to be taken with food, while others need to be taken on an empty stomach. Always read the patient information leaflet that comes with your medicine.

Alcohol

It's a good idea to avoid drinking alcohol when taking medicine or feeling unwell.

But it's unlikely that drinking alcohol in moderation will cause problems if you're taking the most common antibiotics.

However, some antibiotics can have side effects such as feeling sick or dizzy, which might be made worse by drinking alcohol.

Ask your GP or pharmacist if you're unsure whether you can drink alcohol while taking antibiotics.

Metronidazole and tinidazole

It's best to completely avoid alcohol while taking:

• metronidazole – an antibiotic sometimes used for dental or vaginal infections, skin infections, infected leg ulcers and pressure sores
• tinidazole – an antibiotic sometimes used to treat many of the same infections as metronidazole, as well as to help clear bacteria called Helicobacter pylori (H. pylori) from the gut

Continue to avoid alcohol for 48 hours after you stop taking metronidazole and 72 hours after you stop taking tinidazole.

Drinking alcohol with metronidazole or tinidazole can cause very unpleasant side effects, such as:

• feeling and being sick
• stomach pain
• hot flushes
• a fast or irregular heartbeat
• headaches
• feeling dizzy
• feeling drowsy

Other antibiotics

It may be best to avoid drinking alcohol if you're taking:

• linezolid – this medicine can be affected by undistilled (fermented) alcoholic drinks, such as wine, beer, sherry and lager
• doxycycline – alcohol can affect this medicine, and it may also be less effective in people with a history of drinking heavily

The contraceptive pill

Some antibiotics, such as rifampicin and rifabutin, can reduce the effectiveness of the contraceptive pill.

If you're prescribed rifampicin or rifabutin, you may need to use additional contraception, such as condoms, while taking antibiotics. Speak to your GP, nurse or pharmacist for advice.

Mixing medicines

Some antibiotics do not mix well with certain medicines and herbal supplements.

You may be prescribed a different antibiotic or told to stop taking some medicines or herbal supplements.

Always read the patient information leaflet that comes with your medicine and tell your doctor if you're taking any medicines or herbal remedies.

Antibiotic resistance

Antibiotics are no longer routinely used to treat infections.

This is because:

• many infections are caused by viruses, so antibiotics are not effective
• antibiotics are often unlikely to speed up the healing process and can cause side effects
• the more antibiotics are used to treat trivial conditions, the more likely they are to become ineffective for treating more serious conditions

Both the NHS and health organisations across the world are trying to reduce the use of antibiotics, especially for health problems that are not serious.

For example, antibiotics are no longer routinely used to treat:

• chest infections
• ear infections in children
• sore throats

Antibiotic resistance and 'superbugs'

The overuse of antibiotics in recent years means they're becoming less effective and has led to the emergence of "superbugs".

These are strains of bacteria that have developed resistance to many different types of antibiotics, including:

• MRSA (methicillin-resistant Staphylococcus aureus)
• Clostridium difficile (C. diff)
• the bacteria that cause multi-drug-resistant tuberculosis

These types of infections can be serious and challenging to treat, and are becoming an increasing cause of disability and death across the world.

The biggest worry is that new strains of bacteria may emerge that cannot be treated by any existing antibiotics.