Phenoxymethylpenicillin

Commonly called penicillin V

Phenoxymethylpenicillin is an antibiotic used to treat different infections caused by bacteria. Find out how to take it safely and possible side effects. Phenoxymethylpenicillin is commonly called Penicillin V.

Type of medicine Also called
  • Antibiotic (to treat infections)
  • Penicillin antibiotic
  • Cilicaine VK®
  • Penicillin V®
  • Phenoxymethylpenicillin (AFT)®

What is penicillin V?

Penicillin V is an antibiotic used to treat bacterial infections such as infections of the throat, chest and skin infections such as cellulitis. It is also given to prevent infection if you have had rheumatic fever, or if you have a weakened immune system (eg, if you have had your spleen removed). Penicillin V works by killing or stopping the growth of bacteria (bugs). Penicillin V belongs to a group of antibiotics called penicillins. Like all antibiotics, penicillin V is not effective against infections caused by viruses. 

Dose

In Aotearoa New Zealand, penicillin V is available as capsules and liquid. 

  • The dose of penicillin V will be different for different people depending on the type of infection and your age.
  • Adults: the usual dose is 500 mg 4 times a day. For a severe infection, you may need 1 gram 4 times a day.
  • Children: the dose for children will depend on their body weight. It is usually given 2 to 4 times a day.
  • Your doctor will advise you on how long to take penicillin V for. It is usually taken for 10 days, but some people require longer treatment.
  • Always take your penicillin V exactly as your doctor has told you. The pharmacy label on your medicine will tell you how much to take, how often to take it, and any special instructions.

How to take penicillin V

  • Penicillin V is best taken 1 or 2 hours before eating food. This is because your body may absorb less penicillin V after a meal, making it less effective.
  • Capsules: swallow the capsule with a glass of water. Do not chew them.
  • Liquid: shake the medicine well. Measure the right amount using an oral syringe or medicine spoon. You can get these from your pharmacy. Do not use a kitchen spoon as it will not give you the right amount. Read more: Tips on how to give medicines to babies and children.
  • Timing: Take penicillin V at the same times each day. Try to space your doses evenly throughout the day.
    • Twice a day: this should be in the morning and in the evening.
    • Three times a day: this should be in the morning, early afternoon and at bedtime.
    • Four times a day: this should be about 4 hours apart, for example 7am, 11am, 3pm and 7pm.
  • Missed dose: If you forget to take your dose at the correct time, take it as soon as you remember. Try to take the correct number of doses each day. Do not take 2 doses at the same time to make up for a forgotten dose.
  • If you are sick: If you are sick (vomit) less than 30 minutes after having a dose of penicillin V, take the same dose again. But, if you are sick more than 30 minutes after taking your dose, you do not need to take another dose. Just take the next one when it is due. If you are vomiting and are worried, contact your doctor or Healthline (0800 611 116) for advice.
  • Finish the course: It is best to take the whole course of antibiotics for the number of days your doctor has told you to. Do not stop taking it, even if you feel your infection has cleared up.
  • Alcohol: You can drink alcohol while taking penicillin V.

Things to consider

Before starting penicillin V

Have ever had an allergic reaction to a medicine, especially a penicillin antibiotic? Talk to your doctor about it.

(Note, 9 out of 10 people who think they have a penicillin allergy do not read more about penicillins and penicillin allergy)

While taking penicillin V

Taking other medicines and supplements

  • Penicillin V can interact with some medications, herbal supplements and rongoā Māori, so check with your doctor or pharmacist before starting penicillin V and before starting any new products.
  • If you are taking the contraceptive pill, the effectiveness of ‘the pill’ can be reduced if you have a bout of being sick (vomiting) or diarrhoea which lasts for more than 24 hours. If this happens, ask your doctor or pharmacist for advice about contraception over the following few days.

Storage

Store your capsules in a cool, dry place, away from direct heat and light. If you have been given liquid medicine, this will have been made up by the pharmacy and you may need to keep it in the fridge – check the instructions on the bottle. Make sure the medicine does not freeze.

Possible side effects of phenoxymethylpenicillin

Like all medicines, penicillin V can cause side effects, although not everyone gets them. Often side effects improve as your body gets used to the new medicine.

Side effects What should I do?
  • Diarrhoea (runny poos), nausea (feeling sick)
  • These usually go away with time.
  • Tell your doctor if they bother you.
  • Tummy upset
  • Try taking your dose with a small amount of food.
  • Fever, joint pain
  • Tell your doctor or ring Healthline 0800 611 116. 
  • Vaginal itching, soreness or discharge (vaginal thrush)
  • Tell your doctor or pharmacist.
  • White or yellow spots or sores in the mouth, or red, painful gums (oral thrush)
  • Tell your doctor or pharmacist
  • Allergic reaction such as skin rash, itching, swelling of the lips, face, and mouth or difficulty breathing
  • Stop taking penicillin V.
  • Tell your doctor immediately or ring Healthline 0800 611 116.
Did you know that you can report a side effect to a medicine to CARM (Centre for Adverse Reactions Monitoring)? Report a side effect to a product.

Learn more

For adults
Phenoxymethylpenicillin NZ Formulary Patient Information, NZ
Cilicaine VK® Medsafe Consumer Information, NZ

For children
Penicillin V for prevention of pneumococcal infection NZ Formulary for Children, NZ
Penicillin V for bacterial infections NZ Formulary for Children, NZ

References

  1. Phenoxymethylpenicillin NZ Formulary, May 2022
  2. Phenoxymethylpenicillin NZ Formulary for Children, May 2022

Additional resources for healthcare professionals

Phenoxymethylpenicillin-AFT Medsafe, NZ
Rheumatic fever in Māori – what can we do better? BPAC, NZ, 2011
Antibiotics guide BPAC, NZ, 2017
Group A Streptococcal Sore Throat Management Guideline. 2019 Update. Auckland, National Heart Foundation of New Zealand, NZ
New Zealand Guidelines for Rheumatic Fever: Diagnosis, Management and Secondary Prevention of Acute Rheumatic Fever and Rheumatic Heart Disease: 2014 Update Heart Foundation of New Zealand, NZ 

Credits: Health Navigator Pharmacists. Reviewed By: Sandra Ponen, BPharm, MPH, Auckland Last reviewed: 08 Jun 2022