Fusidic Acid

# Fusidic acid ## Overview - **Classification**: Antibiotic, Fusidanic acid derivative. - **Mechanism**: Inhibits bacterial protein synthesis by interfering with elongation factor G (EF-G) and ribosomal translocation. ## Primary Indications 1. **Skin and Soft Tissue Infections**: Treatment of infections caused by susceptible *Staphylococcus* species (e.g., impetigo, cellulitis). 2. **Bone and Joint Infections**: Often used in combination for staphylococcal osteomyelitis or prosthetic joint infections. 3. **Ocular Infections**: Topical forms used for bacterial conjunctivitis, blepharitis. ## Adult Dosing ### Standard Dosing **Systemic Infections (e.g., severe skin/soft tissue, bone/joint)** - **Dose**: **500 mg** - **Frequency**: **Three times daily (TID)** - **Route**: Oral - **Duration**: 7-14 days for skin, longer for bone/joint (weeks to months). - **Max Dose**: **1500 mg/day**. **Topical Skin Infections (e.g., impetigo)** - **Dose**: Apply a thin layer - **Frequency**: **2-3 times daily** - **Route**: Topical cream/ointment - **Duration**: 7-10 days. **Ocular Infections (e.g., conjunctivitis)** - **Dose**: 1 drop - **Frequency**: **Twice daily** - **Route**: Ophthalmic solution - **Duration**: Usually 7 days. ### Dose Adjustments - **Renal Impairment**: No dose adjustment typically required. - **Hepatic Impairment**: Use with caution. Consider dose reduction or avoidance in severe impairment; monitor LFTs. - **Elderly Patients**: No specific dose adjustment; monitor for adverse effects. ## Pediatric Dosing ### Neonates (0-28 days) - **Dose**: **15-20 mg/kg/dose** - **Frequency**: **Three times daily (TID)** - **Maximum**: Limited data; use with caution. - **Special Notes**: Use with extreme caution due to immature hepatic function and potential for hyperbilirubinemia. ### Infants (1-12 months) - **Dose**: **20 mg/kg/dose** - **Frequency**: **Three times daily (TID)** - **Maximum**: **500 mg/dose**. ### Children (1-12 years) - **Dose**: **20 mg/kg/dose** - **Frequency**: **Three times daily (TID)** - **Maximum**: **500 mg/dose** or **1500 mg/day** (approaching adult dose). ### Adolescents (13-18 years) - **Dose**: Adult dosing, typically **500 mg** - **Frequency**: **Three times daily (TID)** - **Maximum**: **1500 mg/day**. ## Safety Information ### Contraindications - **Absolute**: Hypersensitivity to fusidic acid or any component. - **Absolute**: Concomitant use with **statins (HMG-CoA reductase inhibitors)**, especially simvastatin, due to rhabdomyolysis risk. - **Relative**: Severe hepatic impairment. ### Common Adverse Effects - **Common (1-10%)**: Nausea, vomiting, diarrhea, abdominal pain, rash, reversible jaundice. - **Serious but Rare**: Rhabdomyolysis (especially with statins), hepatic dysfunction, thrombophlebitis (IV). ### Key Drug Interactions - **Statins (e.g., Simvastatin, Atorvastatin)**: Greatly increased risk of rhabdomyolysis. **CONTRAINDICATED**. Statins must be paused during fusidic acid treatment. - **Oral Anticoagulants (e.g., Warfarin)**: May increase INR. Monitor INR closely, adjust anticoagulant dose. - **HIV Protease Inhibitors (e.g., Ritonavir, Saquinavir)**: Increased fusidic acid levels. Monitor for adverse effects. - **Ciclosporin**: Increased ciclosporin levels. Monitor levels and adjust dose as needed. ## Monitoring & Follow-up - **Before Treatment**: Baseline Liver Function Tests (LFTs - AST, ALT, bilirubin). - **During Treatment**: Monitor LFTs weekly, especially if treatment exceeds 1 week or in hepatic impairment. - **Clinical Signs**: Monitor for jaundice, dark urine, severe muscle pain/weakness, or worsening infection. ## Clinical Pearls - 💡 **Administer with food** to minimize gastrointestinal upset. - 💡 **Bitter taste**: Oral suspension is notably bitter; counsel patients on masking if necessary. - 💡 **Resistance prevention**: Often used in combination with other anti-staphylococcal agents to prevent resistance, especially in long-term therapy. - 💡 **Topical application**: For skin infections, ensure area is clean before applying cream/ointment. > **⚠️ Important**: This information is for educational purposes only. Always consult current prescribing information, local guidelines, and clinical judgment before prescribing.