Flucloxacillin

Class: Narrow-spectrum, beta-lactamase-resistant penicillin (antistaphylococcal penicillin)

Mechanism of Action: Inhibits bacterial cell wall synthesis by binding to penicillin-binding proteins (PBPs), leading to bacterial lysis. Resistant to staphylococcal beta-lactamase.

Indications

• Skin and soft tissue infections (cellulitis, impetigo, abscess)
• Bone and joint infections (osteomyelitis, septic arthritis)
• Endocarditis caused by susceptible Staphylococcus aureus
• Respiratory tract infections due to penicillinase-producing staphylococci
• Wound infections, post-surgical infections

Dosage

• Adults: 250–500 mg orally every 6 hours; IV/IM: 0.5–2 g every 6 hours (up to 8 g/day)
• Children: 25–50 mg/kg/day divided every 6 hours (max 100 mg/kg/day)
• Neonates: 25–50 mg/kg every 12 hours (first week of life), then every 8 hours

Maximum Dose

Up to 8 g/day in adults (IV/IM)

Major Side Effects

• GI upset (nausea, diarrhea, epigastric discomfort)
• Hypersensitivity reactions (rash, urticaria, anaphylaxis)
• Hepatotoxicity (cholestatic jaundice, hepatitis – more common with prolonged use)
• Nephritis (rare)
• Injection site pain and phlebitis (IV)

Contraindications

• Hypersensitivity to penicillins or beta-lactams
• History of flucloxacillin-associated jaundice or hepatic dysfunction

Compatible Fluids

• 0.9% Sodium Chloride
• 5% Dextrose
• Water for injection (for reconstitution)

Route of Administration

• Oral (capsule, suspension)
• Intravenous (IV)
• Intramuscular (IM)

Type of Administration

• Oral: Best taken on an empty stomach (1 hour before or 2 hours after meals)
• IV: slow injection (3–4 minutes) or infusion (30–60 minutes)
• IM: deep intramuscular injection

Special Precautions

• Monitor liver function during prolonged therapy
• Adjust dose in severe renal impairment
• Use with caution in elderly patients (higher risk of hepatotoxicity)
• Cross-reactivity risk in patients with cephalosporin allergy