Flucloxacillin for Tonsillitis: Indications, Dosing, and Stewardship

Flucloxacillin is a narrow-spectrum, beta-lactamase-stable penicillin active against Staphylococcus aureus (MSSA) and streptococci. It is not first-line for typical tonsillitis.

Appropriate Use

• Recurrent/persistent tonsillitis with documented S. aureus involvement.
• Peritonsillar abscess (quinsy): Often polymicrobial; flucloxacillin covers staphylococci; usually combined with metronidazole for anaerobes.
• Penicillin-allergic patients (non-anaphylactic): Not an option – use macrolide/clindamycin.

Standard First-Line for Streptococcal Tonsillitis

• Phenoxymethylpenicillin (Penicillin V) 500 mg BID × 10 days (adults).
• Amoxicillin (often preferred for palatability in children).

Dosing (Flucloxacillin)

• Adults: 500 mg–1 g QDS (every 6 hours) on empty stomach (30 min before/2 hr after food).
• Children: 25–50 mg/kg/day divided QDS.
• Duration: 5–10 days; complete course to prevent resistance.

Key Points

• Narrow spectrum preserves microbiome; avoid for viral tonsillitis.
• Monitor for cholestatic hepatitis (rare, >2 weeks, elderly).
• True penicillin allergy: avoid all beta-lactams (cross-reactivity ~1-2% with cephalosporins).