Flucloxacillin: clinical use

Prescribing considerations

• Confirm the indication is compatible with susceptible Gram-positive infection and obtain cultures where appropriate.
• Review previous immediate or severe beta-lactam reactions and any history of flucloxacillin-related hepatic injury.
• Use caution in hepatic dysfunction, severe renal impairment and patients with risk factors for flucloxacillin-associated liver injury.
• Consider sodium exposure from capsules, oral solutions and injectable products where sodium restriction is clinically important.
• Higher systemic exposure increases neurotoxicity and hypokalaemia risks; injectable formulations require attention to route-specific preparation and compatibility.

Contraindications and cautions

• Hypersensitivity to flucloxacillin, product excipients or beta-lactam antibiotics such as penicillins or cephalosporins.
• Previous flucloxacillin-associated jaundice or hepatic dysfunction.
• Ocular or subconjunctival administration of the injectable product.

Monitoring

• Monitor hepatic and renal function during prolonged treatment.
• Monitor potassium when systemic exposure is high or hypokalaemia risk factors are present.
• If combined with paracetamol in a high-risk patient, monitor for acid-base disturbance and high-anion-gap metabolic acidosis.
• Monitor INR when clinically indicated in patients receiving warfarin.
• Monitor for blood-count abnormalities during prolonged or intensive therapy where clinically appropriate.

Clinical pharmacology

Flucloxacillin is a narrow-spectrum, beta-lactamase-resistant isoxazolyl penicillin. It inhibits bacterial cell-wall synthesis, is highly protein bound and is eliminated mainly through the kidneys, with some biliary excretion. Renal failure delays elimination, although it is not significantly removed by haemodialysis.

Formulation and product differences

• Capsules are taken whole with water; selected capsule products contain sodium.
• Oral powders are reconstituted as liquids. Selected products include sucrose-containing and sugar-free formulations with different excipients and sodium content.
• Selected reconstituted oral solutions require refrigerated storage and have a limited in-use shelf life; follow the dispensing label.
• The injectable product contains sodium and is intended for preparation and administration by trained healthcare professionals. It must not be mixed with incompatible medicines or protein-containing fluids.

Capsule

Route: Oral

Strengths: 250 mg, 500 mg

Oral solution

Route: Oral

Strengths: 125 mg/5 mL, 250 mg/5 mL