Flucloxacillin

Antistaphylococcal Penicillin·Infectious Diseases - Penicillins

Skin and soft tissue infections, MSSA bacteremia/endocarditis, osteomyelitis

PBSBETA-LACTAMFlopen, Staphylex250 mgS4+1

Max Dose

8 g/day (IV)

Half-life

1 h

Phlebitis

HIGH RISK

Empty Stomach

MANDATORY

Rapid Summary

Overview

Narrow-spectrum, highly potent anti-staphylococcal penicillin. The definitive first-line treatment for MSSA bacteremia and severe cellulitis.

Maximum Dose

Max 8 g/day (IV) or 4 g/day (PO).

Clinical Focus

Given IV, it destroys peripheral veins. Given PO, it has terrible bioavailability and MUST be taken on an empty stomach.

Bottom Line

Flucloxacillin is the first-line antistaphylococcal penicillin for skin and soft tissue infections, but carries a significant risk of cholestatic hepatitis especially with courses > 14 days.

Formulation & Access

Brand Names

Flopen, Staphylex

Oral Routes

Capsules (250 mg, 500 mg).

Parenteral

Ampoules (1 g, 2 g) for IV use.

Prescribing & PBS

Unrestricted General Benefit (S4).

Indications & Use

Primary

PBSTGA

Skin and soft tissue infections, MSSA bacteremia/endocarditis, osteomyelitis.

Clinical Place

Unmatched efficacy against Methicillin-Susceptible S. aureus (MSSA). Superior to Vancomycin for MSSA.

Quick reference

Class & Role

Antistaphylococcal Penicillin — Narrow-spectrum, highly potent anti-staphylococcal penicillin.

Route / Formulation

Capsules (250 mg, 500 mg). (Flopen, Staphylex)

Usual Dose & Max

IV 2 g q6h (8 g/day). Max 8 g/day (IV) or 4 g/day (PO).

Key Indication Doses

Severe Cellulitis / MSSA Bacteremia: IV 2 g q6h (8 g/day). Mild/Moderate Skin Infection: PO 500 mg to 1 g QID. Strictly 1 hr before or 2 hrs after food. Renal Impairment: Reduce IV dose to 1 g q6h or q8h if eGFR < 30.

Best Uses

Flucloxacillin is the first-line antistaphylococcal penicillin for skin and soft tissue infections, but carries a significant risk of cholestatic hepatitis especially with courses > 14 days.

Avoid / Cautions

History of flucloxacillin-induced hepatic dysfunction, severe penicillin allergy. Pregnancy Category B1.

Key Risks

Tissue: Severe chemical phlebitis and vein thrombosis via peripheral IV. Hepatic: Cholestatic hepatitis. Risk increases with age > 55 and courses > 14 days. Renal: Interstitial nephritis.

Key Interactions

Paracetamol. Co-administration of IV Flucloxacillin and high-dose Paracetamol in malnourished/elderly women can trigger severe High Anion Gap Metabolic Acidosis (HAGMA) due to 5-oxoproline accumulation.

Monitoring

Monitor LFTs regularly if used IV for prolonged periods (e.g., osteomyelitis). Inspect peripheral IV cannula sites strictly every shift for redness/pain.

Clinical Pearl

Oral flucloxacillin absorption drops by 50% if taken with food. Ward nurses routinely give it with meals to prevent nausea, guaranteeing sub-therapeutic blood levels and clinical failure. Prescribe it exactly 1 hr before meals.

Access

Flopen, Staphylex250 mg

Brand: Flopen, Staphylex
Formulation: Capsules (250 mg, 500 mg)

Flucloxacillin

Antistaphylococcal Penicillin·Infectious Diseases - Penicillins

Skin and soft tissue infections, MSSA bacteremia/endocarditis, osteomyelitis

PBSBETA-LACTAMFlopen, Staphylex250 mgS4+1

Max Dose

8 g/day (IV)

Half-life

1 h

Phlebitis

HIGH RISK

Empty Stomach

MANDATORY

Rapid Summary

Overview

Narrow-spectrum, highly potent anti-staphylococcal penicillin. The definitive first-line treatment for MSSA bacteremia and severe cellulitis.

Maximum Dose

Max 8 g/day (IV) or 4 g/day (PO).

Clinical Focus

Given IV, it destroys peripheral veins. Given PO, it has terrible bioavailability and MUST be taken on an empty stomach.

Bottom Line

Flucloxacillin is the first-line antistaphylococcal penicillin for skin and soft tissue infections, but carries a significant risk of cholestatic hepatitis especially with courses > 14 days.

Formulation & Access

Brand Names

Flopen, Staphylex

Oral Routes

Capsules (250 mg, 500 mg).

Parenteral

Ampoules (1 g, 2 g) for IV use.

Prescribing & PBS

Unrestricted General Benefit (S4).

Indications & Use

Primary

PBSTGA

Skin and soft tissue infections, MSSA bacteremia/endocarditis, osteomyelitis.

Clinical Place

Unmatched efficacy against Methicillin-Susceptible S. aureus (MSSA). Superior to Vancomycin for MSSA.

Quick reference

Class & Role

Antistaphylococcal Penicillin — Narrow-spectrum, highly potent anti-staphylococcal penicillin.

Route / Formulation

Capsules (250 mg, 500 mg). (Flopen, Staphylex)

Usual Dose & Max

IV 2 g q6h (8 g/day). Max 8 g/day (IV) or 4 g/day (PO).

Key Indication Doses

Best Uses

Flucloxacillin is the first-line antistaphylococcal penicillin for skin and soft tissue infections, but carries a significant risk of cholestatic hepatitis especially with courses > 14 days.

Avoid / Cautions

History of flucloxacillin-induced hepatic dysfunction, severe penicillin allergy. Pregnancy Category B1.

Key Risks

Tissue: Severe chemical phlebitis and vein thrombosis via peripheral IV. Hepatic: Cholestatic hepatitis. Risk increases with age > 55 and courses > 14 days. Renal: Interstitial nephritis.

Key Interactions

Monitoring

Monitor LFTs regularly if used IV for prolonged periods (e.g., osteomyelitis). Inspect peripheral IV cannula sites strictly every shift for redness/pain.

Clinical Pearl

Access

Flopen, Staphylex250 mg

Brand: Flopen, Staphylex
Formulation: Capsules (250 mg, 500 mg)