Phenoxymethylpenicillin

Commonly called penicillin V

Easy-to-read medicine information about phenoxymethylpenicillin (penicillin V) – what it is, how to take phenoxymethylpenicillin safely and possible side effects.

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

Dose

  • 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 250 to 500 mg four times a day. For a severe infection, you may need 1 gram four 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 (usually for 10 days, but some people may require treatment for longer).
  • 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 one hour 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.
  • 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 each day: this should be in the morning, early afternoon and at bedtime.
    • Four times each day: this should be about 4 hours apart, for example 7am, 11am, 3pm and 7pm.
  • If you forget to take your dose at the correct time, take one as soon as you remember. Try to take the correct number of doses each day. Do not take two doses at the same time to make up for a forgotten dose.
  • 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 (vomit) and it is more than 30 minutes after having a dose of penicillin V, you do not need to take another dose. Wait until the next normal dose.
  • If you are vomiting and are worried, contact your doctor or HealthLine (0800 611 116) for advice.

Other tips

  • 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.
  • 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.

Precautions – before starting penicillin V

  • Have ever had an allergic reaction to a medicine, especially a penicillin antibiotic?
  • Do you have any problems with your liver or kidneys?
  • Are taking any other medicines? This includes any medicines you are taking which you can buy without a prescription, as well as herbal and complementary medicines.

If so, it’s important that you tell your doctor or pharmacist before you start penicillin V. Sometimes a medicine isn’t suitable for a person with certain conditions, or it can only be used with extra care.

Possible side effects

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 may go away with time.
  • Tell your doctor if troublesome.
  • 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 

Interactions

Penicillin V may interact with a few medications and herbal supplements, so check with your doctor or pharmacist before starting penicillin V or before starting any new medicines. 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.

Learn more

For adults
Phenoxymethylpenicillin New Zealand Formulary Patient Information
Cilicaine VK® Medsafe Consumer Information

For children
Penicillin V for prevention of pneumococcal infection New Zealand Formulary for Children
Penicillin V for bacterial infections New Zealand Formulary for Children

References

  1. Phenoxymethylpenicillin New Zealand Formulary
  2. Phenoxymethylpenicillin New Zealand Formulary for Children
Credits: Sandra Ponen, Pharmacist. Reviewed By: Angela Lambie, Pharmacist, Auckland Last reviewed: 05 Apr 2019