What is the recommended treatment and dosage of fusidic acid for skin and soft tissue infections?

Recommended Treatment and Dosage of Fusidic Acid for Skin and Soft Tissue Infections

For skin and soft tissue infections, fusidic acid is recommended at a dosage of 500 mg orally three times daily or 750 mg twice daily for adults, with treatment duration of 7-14 days. 1

Indications for Fusidic Acid

Fusidic acid is particularly effective for treating:

• Mild to moderately severe skin and soft tissue infections 2
• Impetigo, folliculitis, erythrasma, furunculosis 2
• Abscesses and infected traumatic wounds 2
• Staphylococcal skin infections, including those caused by MRSA 1

Dosage Recommendations

Adults:

• Oral therapy: 500 mg PO every 8 hours or 750 mg PO every 12 hours 1
• For osteomyelitis (when combined with rifampin): 500 mg PO every 8 hours or 750 mg every 12 hours + Rifampin 600 mg PO daily or 300-450 mg PO every 12 hours 1

Children:

• For children <1 year: 50 mg/kg/day PO divided every 8 hours 1
• For children 1-5 years: 250 mg PO every 8 hours 1
• For children 6-12 years: 500 mg PO every 8 hours 1
• Alternative pediatric dosing: 20 mg/kg/day divided into two daily doses (improved tolerability compared to three times daily dosing) 3

Duration of Treatment

• For uncomplicated skin and soft tissue infections: 5-10 days 1
• For more complicated infections: 7-14 days 1
• Treatment should not exceed 14 days at a time to minimize resistance development 4

Antimicrobial Activity

• Fusidic acid has potent activity against Staphylococcus aureus, including MRSA 2, 5
• It has marginal activity against Streptococcus pyogenes, with clinical cure rates of 75-85% for streptococcal infections compared to 91-99% for staphylococcal infections 5
• No cross-resistance or cross-allergy has been observed with other antibiotics in routine clinical use 2

Formulations

• Oral tablets: 250 mg (typically dosed at 500 mg per administration) 4
• Oral suspension: For pediatric use 3, 4
• Topical cream or ointment: Applied 2-3 times daily for conditions like impetigo 4
• Combination formulations with corticosteroids (1% hydrocortisone or 0.1% betamethasone) for infected eczema 2, 4

Special Considerations

• Fusidic acid has a steroid-like structure that contributes to high tissue penetration, but it does not possess any steroid activity 2
• Subinhibitory concentrations of fusidic acid may reduce S. aureus virulence by inhibiting biofilm formation and α-toxin expression 6
• The twice-daily regimen has significantly better tolerance than three times daily dosing in children 3
• Resistance development can be minimized by restricting therapy to no more than 14 days 4

Limitations and Alternative Therapies

• Fusidic acid is less useful for conditions such as hidradenitis suppurativa, chronic leg ulcers, burns, and pressure sores 2
• For MRSA infections, alternatives include:
  • TMP-SMX (160-320/800-1600 mg PO every 12 hours) 1
  • Doxycycline (100 mg PO every 12 hours) 1
  • Minocycline (200 mg loading dose, then 100 mg PO every 12 hours) 1
  • Linezolid (600 mg PO every 12 hours) 1

Monitoring and Follow-up

• Clinical response should be evident within 48-72 hours of starting therapy 1
• If no improvement is seen within this timeframe, consider alternative antibiotics or drainage procedures 1
• For complicated infections, follow-up cultures may be necessary to ensure bacterial eradication 1