BMA Concise Guide to Medicine & Drugs

Phenoxymethylpenicillin

Brand name None

Used in the following combined preparations None

QUICK REFERENCE

Drug group Penicillin antibiotic

Overdose danger rating Low

Dependence rating Low

Prescription needed Yes

Available as generic Yes

GENERAL INFORMATION

Phenoxymethylpenicillin, also known as Penicillin V, is a synthetic penicillin-type antibiotic that is prescribed for a wide range of infections. It is only given by mouth and was the first orally active penicillin to be synthesized.

Various commonly occurring respiratory tract infections, such as some types of tonsillitis and pharyngitis, as well as ear infections, often respond well to this drug.

Phenoxymethylpenicillin is also used to treat less common infections caused by the Streptococcus bacterium, such as scarlet fever and erysipelas (a skin infection). It is also prescribed long-term to prevent the recurrence of rheumatic fever, a rare, although potentially serious condition. It is also used long-term to prevent infections following removal of the spleen or in sickle cell disease.

As with other penicillin antibiotics, the most serious adverse effect that may rarely occur is an allergic reaction that may cause collapse, wheezing, and a rash in susceptible people.

INFORMATION FOR USERS

Your drug prescription is tailored for you. Do not alter dosage without checking with your doctor.

How taken/used Tablets, liquid.

Frequency and timing of doses 4 x daily, at least 30 minutes before food.

Dosage range Adults 2–4g daily. Children Reduced dose according to age.

Onset of effect Within a few hours.

Duration of action Up to 12 hours.

Diet advice None.

Storage Keep in original container at room temperature out of the reach of children.

Missed dose Take as soon as you remember. If your next dose is due within 2 hours, take a single dose now and skip the next.

Stopping the drug Take the full course. Even if you feel better, the original infection may still be present and may recur if the treatment is stopped too soon.

Exceeding the dose An occasional unintentional extra dose is unlikely to be a cause for concern. But if you notice any unusual symptoms, or if a large overdose has been taken, notify your doctor.

POSSIBLE ADVERSE EFFECTS

Most people do not experience any serious adverse effects with phenoxymethylpenicillin. The most common adverse effects are nausea and vomiting, and diarrhoea may also occur. Discuss with your doctor if these are severe. Rarely it may provoke a serious allergic reaction called anaphylaxis. If you develop a rash, itching, wheezing or breathing difficulties, stop taking the drug and seek immediate medical attention.

INTERACTIONS

Oral contraceptives Phenoxymethylpenicillin may reduce the contraceptive effect of these drugs. Discuss with your doctor.

Probenecid increases the level of phenoxymethylpenicillin in the blood.

Neomycin reduces the level of phenoxymethylpenicillin in the blood.

Methotrexate Excretion of this drug may be greatly reduced by phenoxymethylpenicillin, leading to toxicity.

SPECIAL PRECAUTIONS

Be sure to tell your doctor if:

· You have a long-term kidney problem.

· You have had a previous allergic reaction to a penicillin or cephalosporin antibiotic.

· You are taking other medicines.

Pregnancy No evidence of risk.

Breast-feeding The drug passes into the breast milk, but at normal doses adverse effects on the baby are unlikely. Discuss with your doctor.

Infants and children Reduced dose necessary.

Over 60 No special problems.

Driving and hazardous work No known problems.

Alcohol No known problems.

PROLONGED USE

Prolonged use may increase the risk of Candida infections and diarrhoea.