Flucloxacillin is active against Gram-positive organisms including penicillinase producing strains. It has little activity against Gram-negative bacilli. Flucloxacillin acts by inhibiting the formation of cell wall of bacteria. Flucloxacillin is isoxazolyl penicillin which combined the properties of resistance to hydrolysis by penicillinase, gastric acid stability and activity against gram-positive bacteria. Flucloxacillin is a bactericidal antibiotic that is particularly useful against penicillinase-producing staphylococci. Flucloxacillin kills bacterial cellwall, thus interfering with peptidoglycan synthesis. Peptidoglycan is a heteropolymeric structure that provides the cell wall with its mechanical stability. The final stage of peptidoglycan synthesis involves the completion of the cross-linking with the terminal glycine residue of the pentaglycin bridge linking to the fourth residue of the pentapeptide (D-alanine). The transpeptidase enzyme that performs this step is inhibited by Flucloxacillin. As a result the bacterial cellwall is weakened, the cell swells and then ruptures. Flucloxacillin resists the action of bacterial penicillinase probably because of the steric hindrance induced by the acyl side chain which prevents the opening of the β- lactam ring.

Flucloxacillin is indicated for the treatment of infections due to Gram-positive organisms, including infections caused by penicillinase producing staphylococci. These indications include:

• Skin and soft tissue infections: Boils, abscess, carbuncles, infected skin conditions (e.g. ulcer, eczema, acne, furunculosis, cellulitis, infected wounds, infected burns, otitis media and externa, impetigo).
• Respiratory tract infections: Pneumonia, lung abscess, empyema, sinusitis, pharyngitis, tonsillitis, quinsy.
• It is also used for the treatment of other infections i.e. osteomyelitis, enteritis, endocarditis, urinary tract infection, meningitis, septicaemia caused by Flucloxacillin-sensitive organisms.
• As a prophylactic agent, it is used during major surgical procedures where appropriate; for example, cardiothoracic and orthopedic surgery.

Oral administration:

• Adult: 250 mg four times daily. Dosage may be doubled in severe infections. In osteomyelitis and endocarditis, up to 8 gm daily is used in 6-8 hourly divided doses.
• Children (2-10 years): 1/2 of adult dose.
• Children (Under 2 years): 1/4 of adult dose.

Parenteral administration:

Adult or Elderly:

• Intramuscular Injection: 250 mg four times daily.
• Intravenous Injection: 250 mg-1 g four times daily by slow injection over 3 to 4 minutes or by intravenous infusion.
• All systemic doses may be doubled in severe infections: doses up to 8 g daily have been suggested for endocarditis or osteomyelitis.

Children:

• 2-10 years: half of the adult dose.
• Under 2 years: a quarter of the adult dose.

Administration

Oral doses should be administered 1 hour before meal.

Flucloxacillin is contraindicated in penicillin hypersensitive patients.

There have been some common side effects of gastrointestinal tract such as nausea, vomiting, diarrhoea, dyspepsia and other minor gastrointestinal disturbances. Besides these rashes, urticaria, purpura, fever, interstitial nephritis, hepatitis and cholestatic jaundice have been reported.

Flucloxacillin should be used with caution in patients with evidence of hepatic dysfunction. Caution should also be exercised in the treatment of patients with an allergic diathesis.

Use in Special Populations

In severe renal failure (creatinine clearance <10 ml/min), a reduction in dose or an extension of dose interval should be considered.

Pregnancy & Lactation

US FDA Pregnancy Category of Flucloxacillin is B. There are, no adequate and well-controlled studies in pregnant women. Because animal reproduction studies are not always predictive of human response, this drug should be used during pregnancy only if clearly needed. Flucloxacillin have been shown to be excreted in human milk. So, caution should be exercised when Flucloxacillin is administered to a lactating mother.