Antibiotics: How much do you really know?

Antibiotics are used to treat or prevent some types of bacterial infections. They work by killing bacteria or preventing them from spreading. But they do not work for everything.

Many mild bacterial infections get better on their own without using antibiotics.

Antibiotics do not work for viral infections such as colds and flu, and most coughs.

Antibiotics are no longer routinely used to treat:

chest infections
ear infections in children
sore throats

Regarding antibiotics, take your doctor’s advice on whether you need them. Antibiotic resistance is a big problem – taking antibiotics when you do not need them can mean they will not work for you in the future.

When antibiotics are needed

Antibiotics may be used to treat bacterial infections that:

are unlikely to clear up without antibiotics
could infect others
could take too long to clear without treatment
carry a risk of more serious complications

People at a high risk of infection may also be given antibiotics as a precaution, known as antibiotic prophylaxis

How to take antibiotics

Take antibiotics as directed on the packet, the patient information leaflet that comes with the medicine, or as instructed by your doctor or pharmacist.

Antibiotics can come as:

tablets, capsules, or a liquid that you drink – these can be used to treat most types of mild to moderate infections in the body
creams, lotions, sprays, and drops – these are often used to treat skin infections and eye or ear infections
injections – these can be given as an injection or through a drip directly into the blood or muscle and are used for more serious infections

Missing a dose of antibiotics

If you forget to take a dose of your antibiotics, check the patient information leaflet that came with your medicine to find out what to do.

If you’re not sure, speak to a pharmacist or a doctor.

In most cases, you can take the dose you missed as soon as you remember and then continue to take your course of antibiotics as usual.

But if it’s almost time for the next dose, skip the missed dose and continue your regular dosing schedule. Do not take a double dose to make up for a missed one.

Accidentally taking an extra dose

There’s an increased risk of side effects if you take 2 doses closer together than recommended.

Accidentally taking 1 extra dose of your antibiotic is unlikely to cause serious harm.

But it will increase your chances of getting side effects, such as pain in your stomach, diarrhea, and feeling or being sick.

If you accidentally take more than 1 extra dose of your antibiotic, are worried, or get severe side effects, speak to your doctor as soon as possible.

Side effects of antibiotics

As with any medicine, antibiotics can cause side effects. Most antibiotics do not cause problems if used properly, and serious side effects are rare.

The common side effects include:

being sick
feeling sick
bloating and indigestion
diarrhea

Some people may be allergic to antibiotics, especially penicillin and another type of antibiotic called cephalosporins.

In rare cases, this can lead to a serious allergic reaction (anaphylaxis) or a medical emergency.

Call 911 or go to the emergency room now if:

you get a skin rash that may include itchy, red, swollen, blistered or peeling skin
you’re wheezing
you get tightness in the 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 the hospital.

Considerations and interactions

Some antibiotics are unsuitable for people with certain medical problems, pregnant women, or breastfeeding.

Tell your healthcare professional if you’re pregnant or breastfeeding so they can prescribe the most suitable antibiotic for you.

Only take antibiotics prescribed for you – never “borrow” them from a friend or family member.

Some antibiotics do not mix well with other medicines, such as the contraceptive pill and alcohol.

Read the information leaflet that comes with your medicine carefully and discuss any concerns with your pharmacist or doctor.

Types of antibiotics

There are hundreds of different types of antibiotics, but most of them can be classified into 6 groups.

Penicillins (such as penicillin, amoxicillin, co-amoxiclav, flucloxacillin, and phenoxymethylpenicillin) – widely used to treat a variety of infections, including skin infections, chest infections, and urinary tract infections
Cephalosporins (such as cefalexin) – are used to treat a wide range of infections, but some are also effective for treating more serious infections, such as sepsis and meningitis
Aminoglycosides (such as gentamicin and tobramycin) – tend only to be used in hospitals to treat very serious illnesses such as sepsis, as they can cause serious side effects, including hearing loss and kidney damage; they’re usually given by injection, but may be given as drops for some ear or eye infections
Tetracyclines (such as tetracycline, doxycycline, and lymecycline) – can be used to treat a wide range of infections but are commonly used to treat acne and a skin condition called rosacea
Macrolides (such as azithromycin, erythromycin, and clarithromycin) – can be particularly useful for treating lung and chest infections, as an alternative for people with a penicillin allergy, or for treating penicillin-resistant strains of bacteria
Fluoroquinolones (such as ciprofloxacin and levofloxacin) – are broad-spectrum antibiotics that were once used to treat a wide range of infections, especially respiratory and urinary tract infections; these antibiotics are no longer used routinely because of the risk of serious side effects

Other antibiotics include chloramphenicol (used for eye and ear infections), fusidic acid (used for skin and eye infections), nitrofurantoin, and trimethoprim (used for urinary tract infections).

Uses

Antibiotics are used to treat or prevent some types of bacterial infections. They’re ineffective against viral infections like 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

Learn about antibiotic resistance and why antibiotics are no longer routinely used to treat infections.

People at risk of bacterial infections

Antibiotics may also be recommended for people 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 with a high infection risk.

For example, you may be prescribed antibiotics if you’re going to have the following:

some types of eye surgery – such as cataract surgery or glaucoma surgery
joint replacement surgery
breast enlargement surgery
pacemaker surgery
surgery to remove the gallbladder
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 with a high chance of becoming infected – an animal or human bite, for example, or a wound that has come into contact with soil or feces.

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 anemia

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 infections
genital herpes
rheumatic fever

Side effects

Antibiotics can have side effects such as diarrhea 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 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 be successfully treated by taking antihistamines.

But if you’re concerned, or your symptoms do not improve with treatment, call your doctor for advice.

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

Call 911 or go to the Emergency room 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 the hospital.

Tetracyclines and sensitivity to light

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

Avoid prolonged exposure to bright light while taking these medicines.

Fluoroquinolones

Severe aches and pains

In 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 doctor if you get serious side effects, 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 at risk of heart valve problems.

Stop taking fluoroquinolone treatment straight away and see your doctor if you get serious side effects, including:

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

Alcohol

It’s a good idea to avoid drinking alcohol when taking medication or feeling unwell.

But it’s unlikely that drinking alcohol in moderation will cause problems if you take the most common antibiotics.

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

Ask your doctor 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 contraceptive pill’s effectiveness.

If you’re prescribed rifampicin or rifabutin, you may need to use additional contraception, such as condoms, while taking antibiotics. Speak to your doctor, 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:

viruses cause many infections, 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 in treating more serious conditions

Health organizations worldwide 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, leading 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 infections can be serious and challenging to treat and are becoming an increasing cause of disability and death worldwide.

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