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  1. About phenoxymethylpenicillin
  2. Key facts
  3. Who can and can't take it
  4. How and when to take it
  5. Side effects
  6. How to cope with side effects
  7. Pregnancy and breastfeeding
  8. Cautions with other medicines
  9. Common questions

1. About phenoxymethylpenicillin

Phenoxymethylpenicillin is a type of penicillin.

It's an antibiotic used to treat bacterial infections, including ear, chest, throat and skin infections.

It can also be used to prevent infections if you have sickle cell disease, or if you have had chorea (a movement disorder), rheumatic fever, or your spleen removed.

The medicine is only available on prescription. It comes as tablets or as a liquid that you drink.

2. Key facts

  • You'll usually take phenoxymethylpenicillin 4 times a day to treat an infection.
  • In most cases you'll start to feel better in a few days.
  • The most common side effects of phenoxymethylpenicillin are feeling sick and diarrhoea.
  • Some people may have an allergic reaction to antibiotics, especially phenoxymethylpenicillin and other penicillins.
  • You can drink alcohol while taking it.
  • Phenoxymethylpenicillin is also known as penicillin V.

3. Who can and can't take it

Most adults and children can take phenoxymethylpenicillin, including pregnant and breastfeeding women.

But phenoxymethylpenicillin isn't suitable for some people. To make sure this medicine is safe for you, tell your doctor if you have:

  • had an allergic reaction to phenoxymethylpenicillin, or any other antibiotics or medicines, in the past
  • kidney problems
  • any allergies
  • asthma

4. How and when to take it

The amount of phenoxymethylpenicillin you need depends on your age and how bad the infection is, and whether you're taking it to treat or prevent an infection.

How much will I take?

For adults and children over 12 years, you'll usually take:

  • 500mg 4 times a day - for treating infections
  • 500mg twice a day - for preventing infections


Carry on taking this medicine until you have completed the course, even if you feel better.

If you stop your treatment early, the infection could come back.

When to take it

Try to space the doses evenly throughout the day. If you take phenoxymethylpenicillin 4 times a day, this could be first thing in the morning, around midday, late afternoon and at bedtime.

If you're taking it twice a day, leave 12 hours between each dose. This could be early morning and early evening, at 8am and 8pm.

It's best not to take phenoxymethylpenicillin at mealtimes. Take it 30 minutes before a meal or at least 2 hours after you have eaten.

How to take it

Swallow phenoxymethylpenicillin tablets whole. Do not chew or break them.

The medicine also comes as a liquid for people who find it difficult to swallow tablets.

If you or your child are taking phenoxymethylpenicillin as a liquid, it'll usually be made up for you by your pharmacist.

The medicine will come with a plastic syringe or spoon to help you measure out the right dose.

If you don't have one, ask your pharmacist for one. Do not use a kitchen teaspoon as it will not give the right amount.

What if I forget to take it?

If you forget to take a dose, take it as soon as you remember, unless it's nearly time for your next dose.

In this case, just leave out the missed dose and take your next dose as normal.

Never take 2 doses at the same time. Never take an extra dose to make up for a forgotten one.

If you forget doses often, it may help to set an alarm to remind you. You could also ask your pharmacist for advice on other ways to remember your medicines.

What if I take too much?

Accidentally taking an extra dose of phenoxymethylpenicillin is unlikely to harm you or your child.

Speak to your pharmacist or doctor if you're worried, or if you take more than 1 extra dose.

5. Side effects

Like all medicines, phenoxymethylpenicillin can cause side effects, although not everyone gets them.

If you're taking phenoxymethylpenicillin to prevent infections, your doctor will usually ask you to have blood tests. This is to make sure you're not getting any unexpected side effects.

Common side effects

These common side effects happen in 1 in 10 people. Keep taking the medicine, but tell your doctor or pharmacist if they bother you or don't go away:

  • feeling sick (nausea)
  • being sick (vomiting) or diarrhoea
  • stomach pain

Serious side effects

Serious side effects are rare and happen in less than 1 in 1,000 people.

Call a doctor straight away if you get:

  • redness and peeling of the skin over large areas of your body
  • stomach pain, fever and a lot of watery diarrhoea with blood and mucus in it

Serious allergic reaction

Around 1 in 10 people have an allergic reaction to phenoxymethylpenicillin.

In most cases, the allergic reaction is mild.

Symptoms may include:

  • a raised, itchy skin rash
  • coughing
  • wheezing

Mild allergic reactions can usually be successfully treated by taking antihistamines.

In rare cases, phenoxymethylpenicillin can cause a serious allergic reaction (anaphylaxis).

Immediate action required: Call 999 or go to A&E 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 hospital.

These aren't all the side effects of phenoxymethylpenicillin.

For a full list, see the leaflet inside your medicines packet.


You can report any suspected side effect to the UK safety scheme.

6. How to cope with side effects

What to do about:

  • feeling sick (nausea) - stick to simple meals and do not eat rich or spicy food while you're taking this medicine.
  • being sick (vomiting) or diarrhoea - drink lots of fluids, such as water or squash, to avoid dehydration. Take small, frequent sips if you're being sick. Signs of dehydration include peeing less than usual or having dark, strong-smelling pee. Do not take any other medicines to treat diarrhoea and vomiting without speaking to a pharmacist or doctor.
  • stomach pain - try to rest and relax. It can help to eat and drink slowly and have smaller and more frequent meals. Putting a heat pad or covered hot water bottle on your stomach may also help. If you're in a lot of pain, speak to your pharmacist or doctor.

7. Pregnancy and breastfeeding

It's usually safe to take phenoxymethylpenicillin during pregnancy and while breastfeeding.


For safety, tell your doctor if you're trying to get pregnant, already pregnant, or breastfeeding.

8. Cautions with other medicines

There are many medicines that don't mix well with phenoxymethylpenicillin.

Tell your doctor if you're taking these medicines before you start taking phenoxymethylpenicillin:

Mixing phenoxymethylpenicillin with herbal remedies and supplements

There are no known problems with taking herbal remedies and supplements with phenoxymethylpenicillin.


For safety, tell your doctor or pharmacist if you're taking any other medicines, including herbal remedies, vitamins or supplements.

9. Common questions

How does phenoxymethylpenicillin work?

Phenoxymethylpenicillin is an antibiotic. It works by killing the bacteria that cause infection.

What if I'm allergic to penicillin?

Tell your doctor or pharmacist if you have had an allergic reaction to penicillin or any other medicine in the past.

If you're allergic to penicillin, you'll be allergic to all penicillin-based medicines, including phenoxymethylpenicillin, and your doctor will prescribe a different type of antibiotic.

When will I feel better?

For most infections, you should feel better within a few days.

It's very important that you keep taking phenoxymethylpenicillin until your course is finished.

Do this even if you feel better. It'll help stop the infection coming back.

What if I don't get better?

Tell your doctor if you don't start feeling better after taking phenoxymethylpenicillin for 3 days.

Also tell them if, at any time, you start to feel worse.

How long will I take it for?

How long you take it for depends on the type of infection you have.

The usual course of phenoxymethylpenicillin lasts for 5 to 10 days.

If you're taking phenoxymethylpenicillin to prevent infection (for example, if you have sickle cell disease or have had chorea, rheumatic fever or your spleen removed), you may have to take it for the rest of your life.

Is it safe to take phenoxymethylpenicillin long term?

Phenoxymethylpenicillin is generally safe when prescribed long term to prevent infections. There are no additional known side effects.

But if you develop diarrhoea that lasts for more than a couple of days, ask your pharmacist or doctor for advice.

How does phenoxymethylpenicillin compare with other antibiotics?

Phenoxymethylpenicillin and other penicillins, like amoxicillin, are antibiotics that are widely used to treat a variety of infections, including skin infections, chest infections and urinary tract infections (UTIs).

Not all antibiotics are suitable for every infection. Your doctor will choose an antibiotic that's suitable for the type of infection you have.

Speak to your pharmacist or doctor if you have any questions.

Will it affect my contraception?

Phenoxymethylpenicillin doesn't stop contraceptive pills working.

But if phenoxymethylpenicillin makes you have severe diarrhoea or vomiting - and you continue to vomit or pass 6 to 8 watery stools over 24 hours - your contraceptive pills may not protect you from pregnancy.

If this happens, follow the instructions in the leaflet that comes with your contraceptive pills.

Read more about what to do if you're on the pill and you're being sick or have diarrhoea.

Will it give me thrush?

Some people get a fungal infection called thrush after taking a course of antibiotics like phenoxymethylpenicillin.

Antibiotics kill the normal harmless bacteria that help to defend against thrush.

Symptoms include redness and itching in the mouth. Women may get vaginal itching.

If this happens to you, talk to your doctor or pharmacist for advice.

Will it affect my fertility?

There's no firm evidence to suggest that taking phenoxymethylpenicillin will reduce fertility in either men or women.

But for safety, speak to a pharmacist or your doctor before taking it if you're trying to get pregnant.

Can I drive or ride a bike while taking it?

Yes, you can. Phenoxymethylpenicillin shouldn't affect you being able to drive or cycle.

Can I drink alcohol with it?

Yes, you can drink alcohol with phenoxymethylpenicillin.

Is there any food or drink I need to avoid?

You can eat and drink normally while taking phenoxymethylpenicillin.

Just remember to take phenoxymethylpenicillin on an empty stomach - either 30 minutes before a meal or at least 2 hours after you have eaten.

Page last reviewed: 6 December 2018
Next review due: 6 December 2021