Flucloxacillin

Flucloxacillin is the standard antibiotic for skin infections such as cellulitis and infected wounds. It has one instruction people get wrong more than any other: it has to be taken on an empty stomach, or a large part of the dose simply does not get absorbed.

What it is used for

Skin and soft tissue infections including cellulitis, infected wounds, infected eczema and impetigo, and some bone and chest infections. It is particularly effective against staphylococcus bacteria.

How to take it — the empty stomach rule

Usually four times a day. Spacing that around meals takes planning — many people use roughly 7am, midday, 5pm and bedtime, adjusting meals around it.

Swallow capsules with a full glass of water, and stay upright for a while afterwards. Finish the whole course.

Side effects

Nausea, diarrhoea and stomach ache are common — awkward, given it cannot be taken with food. If it is severe, speak to us rather than starting to take it with meals.

Get medical advice for:

• Yellowing of the eyes or skin, dark urine, pale stools, or itching — flucloxacillin can rarely cause liver problems, sometimes appearing up to two months after the course ends
• Severe or bloody diarrhoea
• A widespread rash, or swelling of the face or throat — call 999 for breathing difficulty

The liver risk is higher in older people and with longer courses, which is why courses are kept as short as effective.

Other points

Tell your prescriber if you have a penicillin allergy — flucloxacillin is a penicillin. A genuine allergy usually means hives, swelling or breathing difficulty rather than nausea or diarrhoea.

It can be used in pregnancy and breastfeeding where indicated.

Come back if the infection is spreading, if a red area is expanding or you develop a fever, or if there is no improvement after two to three days.

Frequently asked questions