BMA Concise Guide to Medicine & Drugs


Brand names Floxapen, Fluclomix, Ladropen

Used in the following combined preparations Co-Fluampicil, Flu-Amp, Magnapen


Drug group Penicillin antibiotic

Overdose danger rating Low

Dependence rating Low

Prescription needed Yes

Available as generic Yes


Flucloxacillin is a penicillin antibiotic. It was developed to deal with staphylococci bacteria that are resistant to other antibiotics. Such bacteria make enzymes (penicillinases) that neutralize the antibiotics but flucloxacillin is not inactivated by penicillinases and is therefore effective for treating penicillin-resistant staphylococcal infections. The drug is used to treat ear infections, pneumonia, impetigo, cellulitis, osteomyelitis, and endocarditis. Flucloxacillin is also available combined in equal parts with ampicillin, which is known as co-fluampicil. This is used for treating mixed infections of penicillinase-producing organisms.

Staphylococci have evolved so that some strains are now resistant to flucloxacillin as well. These are the so-called methicillin-resistant Staphylococcus aureus infections (MRSA). Only a few antibiotics held in reserve can deal with them.


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

How taken/used Capsules, liquid, injection.

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

Adult dosage range 1–2g daily (oral); 1–8g daily (injection); 8–12g daily (endocarditis).

Onset of effect 30 minutes.

Duration of action 4–6 hours.

Diet advice Make sure you keep well hydrated.

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

Missed dose Take as soon as you remember. Take your next dose at the scheduled time.

Stopping the drug Take the full course. Even if you feel better, the original infection may still be present and symptoms may recur if 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.


The most common adverse effects of flucloxacillin are gastrointestinal: diarrhoea and nausea. Other adverse effects include abdominal pain, bruising, sore throat, and fever. Consult your doctor if you experience any of these symptoms or if gastrointestinal symptoms are severe. If you develop a rash, itching, breathing difficulties, wheezing, or swollen joints (all signs of a allergic reaction), stop taking the drug and contact your doctor at once. If jaundice occurs, even weeks or months after treatment, consult your doctor promptly and stop taking the drug if you have not already done so.


Probenecid This drug reduces the excretion of flucloxacillin, thereby prolonging its effects.

Oral contraceptives Flucloxacillin may reduce the effectiveness of combined oral contraceptives.

Oral typhoid vaccine Flucloxacillin inactivates the vaccine. Avoid taking flucloxacillin for 3 days before and after having the vaccine.

Methotrexate Flucloxacillin reduces the excretion of methotrexate, thereby increasing the risk of toxicity.


Be sure to tell your doctor if:

· You are allergic to penicillin antibiotics or cephalosporin antibiotics.

· You have a history of allergy.

· You have liver problems, or have had previous liver problems with flucloxacillin.

· You are taking other medicines.

Pregnancy No evidence of risk.

Breast-feeding No evidence of risk.

Infants and children Reduced dose necessary.

Over 60 No known problems.

Driving and hazardous work No known problems.

Alcohol No known problems.


Although the drug is not normally necessary for long-term use, osteomyelitis and endocarditis may require longer than usual courses of treatment.

Monitoring Regular tests of liver and kidney function will be performed if a longer course of treatment is prescribed.