ATC Code J01CF05
Formula C19H17FClN3O5S
Molar Mass (g·mol−1) 453,87
Physical State solid
PKS Value 2,7
CAS Number 5250-39-5
PUB Number 21319
Drugbank ID DB00301


Flucloxacillin is a penicillin antibiotic with a narrow spectrum of activity that is specifically effective against Gram-positive organisms. It is indicated for the treatment of skin infections, external ear infections, leg ulcer infections, diabetic foot infections, and bone infections. It may be used with other medications to treat pneumonia and endocarditis. Flucloxacillin cannot be used for methicillin-resistant Staphylococcus aureus (MRSA) infections. It is administered orally or parenterally.

The substance was developed because of increasing bacterial resistance to established antibiotics. Flucloxacillin was patented in 1961 and was first marketed in Europe in the 1970s.



Like other β-lactam antibiotics, flucloxacillin acts by inhibiting the synthesis of bacterial cell walls. It inhibits cross-linking between linear peptidoglycan polymer chains by binding to specific penicillin-binding proteins (PBPs) found in the bacterial cell wall. These peptidoglycan chains form a major component of the cell wall of Gram-positive bacteria. Inhibition prevents the bacteria from forming a stable cell wall and causes them to die.

Flucloxacillin is more acid stable than many other penicillins and can be administered orally in addition to parenteral administration.


The bioavailability of flucloxacillin is 50-70% after oral administration. It is metabolized in the liver. The half-life is approximately 0.75-1 h and the drug is ultimately excreted via the kidneys and urine.

Drug Interactions

Flucloxacillin may decrease the excretion of methotrexate, resulting in an increased risk of toxicity symptoms and increased side effects.

Flucloxacillin levels in the blood may increase in renal failure and with the use of probenecid, leading to increased side effects.


Side effects

Common side effects associated with the use of flucloxacillin include:

  • Diarrhea
  • Nausea
  • Skin rash
  • Urticaria
  • Pain
  • Injection site reactions
  • Superinfection (including candidiasis)
  • Temporary elevation of liver enzymes and bilirubin.

A less common side effect is cholestatic jaundice (jaundice).

Contraindications and precautions

Flucloxacillin is contraindicated in individuals allergic to penicillins, cephalosporins, or carbapenems. Flucloxacillin should also not be used on the eye or in individuals with a history of cholestatic hepatitis associated with the use of dicloxacillin or flucloxacillin.

Because of the risk of cholestatic hepatitis, it should be used with caution in the elderly, in patients with impaired renal function in whom a reduced dose is required, and in patients with impaired hepatic function, after careful consideration of the cost-benefit risk.

It should be taken on an empty stomach, one-half to one hour before food, as absorption is reduced when taken with food.

Markus Falkenstätter

Markus Falkenstätter

Markus Falkenstätter ist Autor zu pharmazeutischen Themen in der Medizin-Redaktion von Medikamio. Er befindet sich im letzten Semester seines Pharmaziestudiums an der Universität Wien und liebt das wissenschaftliche Arbeiten im Bereich der Naturwissenschaften.

Mag. pharm Stefanie Lehenauer

Mag. pharm Stefanie Lehenauer

Stefanie Lehenauer ist seit 2020 freie Autorin bei Medikamio und studierte Pharmazie an der Universität Wien. Sie arbeitet als Apothekerin in Wien und ihre Leidenschaft sind pflanzliche Arzneimittel und deren Wirkung.

Your personal medicine assistent

afgis-Qualitätslogo mit Ablauf Jahr/Monat: Mit einem Klick auf das Logo öffnet sich ein neues Bildschirmfenster mit Informationen über Medikamio GmbH & Co KG und sein/ihr Internet-Angebot: medikamio.com/ This website is certified by Health On the Net Foundation. Click to verify.

Search our database for drugs, sorted from A-Z with their effects and ingredients.


All substances with their common uses, chemical components and medical products which contain them.


Causes, symptoms and treatment for the most common diseases and injuries.

The contents shown do not replace the original package insert of the medicinal product, especially with regard to dosage and effect of the individual products. We cannot assume any liability for the correctness of the data, as the data was partly converted automatically. A doctor should always be consulted for diagnoses and other health questions. Further information on this topic can be found here.