Meds and you

27 September 2013


Phenoxymethylpenicillin is a penicillin antibiotic.


(Also known as Penicillin V)

Phenoxymethylpenicillin is the active ingredient of Betapen (Nappi Code: 780081-013 & 751111-014), Len V.K. (Nappi Code: 736635-017 & 830089-004), Spec-Pen-VK 250 (Nappi Code: 700174- 006).

General information

Penicillins are antibiotics that are derived from a mold. It is used to treat infections caused by harmful bacteria. In South Africa phenoxymethylpenicillin is registered for the treatment of bacterial infections caused by susceptible organisms including tonsillitis, pharyngitis and for the prevention of rheumatic fever after a streptococcal infection.

Should you develop a skin rash whilst being treated with this medication, you should notify your doctor to rule out the possibility of allergy.

A penicillin allergy may lead to fever, swelling of the mouth and tongue, itching and associated breathing difficulties.

Phenoxymethylpenicillin is only effective against bacterial infections and is useless for treating viral infections such as cold or flu.

Antibiotic resistance occurs when a bacterium develops the ability to defend itself against the effect of an antibiotic. It occurs frequently with this antibiotic. The most common causes for resistance is patients not completing prescribed antibiotic courses allowing the bacteria to recover from treatment, and the use of antibiotics for non-bacterial infections such as cold and flu.

This antibiotic is best absorbed if taken on an empty stomach. To prevent a reduction of absorption into the body, it should be taken at least 60 minutes before or 3 hours after a meal.

How does phenoxymethylpenicillin work?
Phenoxymethylpenicillin functions by changing the structure of the bacterial cell wall, allowing fluid to penetrate into the cell. As a result the bacterial cell literally ruptures.

Fast facts

Drug schedule: schedule 4
Available as: phenoxymethylpenicillin is available as tablets and suspension.
What does it do? Phenoxymethylpenicillin has an antibiotic effect.
Overdose risk: low
Dependence risk: low
Is Phenoxymethylpenicillin available as a generic? yes
Is Phenoxymethylpenicillin available on prescription only? yes

User information

Onset of effect: within 4 hours
Duration of action: up to 12 hours
Dietary advice: This drug should best be taken on an empty stomach
Stopping this medicine: complete the full course as prescribed by your doctor, even if you feel better within a few days. Premature discontinuation may cause symptoms to recur, or cause bacterial resistance.
Prolonged use: phenoxymethylpenicillin is generally given as short courses only. Prolonged use may increase the risk of a medicine-resistant infection.

Special precautions
Consult your doctor before using this drug if:

  • you have a known allergy to penicillin or cephalosporin antibiotics

  • you have kidney or liver disease

Pregnancy: avoid. It is unknown how this medication may affect your baby. Consult your doctor before using this drug, or if you are planning to fall pregnant.
Breastfeeding: avoid. This medication is passed through breast milk and may affect your baby adversely. Consult your doctor before use.
Porphyria: this medication is safe to use.
Infants and children: this medication is safe for use in children at the recommended dose.
The elderly: no special precautions need to be taken.
Driving and hazardous work: no special precautions need to be taken.
Alcohol: no special precautions need to be taken.

Possible side effects

Side Effect

Consult your doctor

Only if severe
In all cases

skin rash


itchy skin


difficulty swallowing






fungal infections


black/hairy tongue




loss of consciousness







allopurinol increased risk of skin rash
chloroquine reduces the efficacy of antibiotic
oral contraceptives possible reduced contraceptive efficacy. Another form of contraceptive is advised.
probenecid increased risk of antibiotic toxicity
tetracycline possible reduced antibiotic efficacy
warfarin increased risk of warfarin toxicity

Disease interactions
Consult your doctor before using this drug if you have a known allergy to penicillin or cephalosporin antibiotics, or if you have kidney or liver disease.

Overdose action
A small overdose is no cause for concern. In case of intentional large overdose seek emergency medical attention.

Recommended dosage
Adults: 1000mg - 2000mg daily in divided doses. Doses of up to 6000mg daily have been used.

This material is not intended to substitute medical advice, but is for informational purposes only. Please consult a physician for specific treatment and recommendations.

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