Flucloxacillin

# Flucloxacillin ## Overview - **Classification**: Penicillin antibiotic, narrow-spectrum beta-lactam. - **Mechanism**: Inhibits bacterial cell wall synthesis by binding to penicillin-binding proteins (PBPs), leading to bacterial lysis. ## Primary Indications 1. **Skin and Soft Tissue Infections** - Cellulitis, abscesses, impetigo, wound infections. 2. **Bone and Joint Infections** - Osteomyelitis, septic arthritis. 3. **Endocarditis** - Treatment of staphylococcal endocarditis. 4. **Other Staphylococcal Infections** - Septicemia, pneumonia. ## Adult Dosing ### Standard Dosing **Mild-Moderate Infections (e.g., Skin & Soft Tissue)** - **Dose**: **250 mg** to **500 mg** - **Frequency**: Every **6 hours** - **Route**: Oral (PO) - **Duration**: Typically 7-14 days **Severe Infections (e.g., Endocarditis, Osteomyelitis)** - **Dose**: **1 g** to **2 g** - **Frequency**: Every **6 hours** - **Route**: Intravenous (IV) - **Duration**: Variable, often weeks for severe infections. - **Maximum Dose**: **12 g/day** ### Dose Adjustments - **Renal Impairment**: - CrCl **>10 mL/min**: No adjustment. - CrCl **<10 mL/min**: Extend interval to every **8-12 hours**. - Hemodialysis/CAPD: Administer after dialysis or per standard dose, extend interval. - **Hepatic Impairment**: Use with **caution**. Monitor liver function tests (LFTs) closely. No specific dose adjustment but may require reduced frequency in severe impairment. - **Elderly Patients**: No specific dose reduction needed, but monitor renal function due to age-related decline. ## Pediatric Dosing ### Neonates (0-28 days) - **Dose**: **25 mg/kg** - **Frequency**: - <7 days old: Every **12 hours** - >7 days old: Every **8 hours** - **Maximum**: Refer to local guidelines; generally **50 mg/kg/day** for neonates. - **Special Notes**: Dosing is highly dependent on post-natal age and gestational age. Use IV route for serious infections. ### Infants (1-12 months) - **Dose**: **12.5 mg/kg** to **25 mg/kg** - **Frequency**: Every **6 hours** - **Maximum**: **500 mg** per dose or **2 g/day** (oral) or **8 g/day** (IV) depending on severity. ### Children (1-12 years) - **Dose**: **12.5 mg/kg** to **25 mg/kg** - **Frequency**: Every **6 hours** - **Maximum**: **1 g** per dose or **4 g/day** (oral) or **12 g/day** (IV). - Typically not to exceed adult max dose. ### Adolescents (13-18 years) - **Dose**: Generally follow **adult dosing guidelines**. - **Maximum**: **Adult maximum dose** (e.g., **12 g/day IV**). ## Safety Information ### Contraindications - **Absolute**: Hypersensitivity to penicillins or other beta-lactam antibiotics. - **Absolute**: History of flucloxacillin-associated jaundice or hepatic dysfunction. ### Common Adverse Effects - **Common (1-10%)**: Diarrhea, nausea, rash (maculopapular), urticaria. - **Uncommon (0.1-1%)**: Vomiting, elevated liver enzymes (transient and asymptomatic). - **Serious but Rare**: Cholestatic jaundice/hepatitis (can be delayed onset, severe, and prolonged), severe cutaneous adverse reactions (SCARs), anaphylaxis, neutropenia, agranulocytosis. ### Key Drug Interactions - **Warfarin**: May **increase INR**; monitor INR closely and adjust warfarin dose as needed. - **Methotrexate**: May **increase methotrexate levels** and toxicity; monitor for adverse effects. - **Oral Contraceptives**: Theoretical risk of **reduced efficacy**; advise additional contraception during and 7 days after. ## Monitoring & Follow-up - **Before Treatment**: Assess for penicillin allergy history. - **During Treatment**: - **LFTs**: Monitor baseline and periodically (e.g., weekly) with prolonged treatment (>2 weeks) or in patients with hepatic impairment. - **Renal Function**: Monitor especially in patients with pre-existing impairment. - **FBC**: Monitor for hematologic effects (rare, but possible with prolonged high doses). - **Clinical Signs**: Watch for signs of rash, jaundice, dark urine, persistent nausea/vomiting, or fever (indicating potential adverse effects). ## Clinical Pearls - 💡 **Oral Absorption**: Take **30-60 minutes before meals** (empty stomach) for optimal absorption. - 💡 **Hepatic Toxicity**: Be aware of **delayed onset cholestatic jaundice**, which can occur weeks after stopping treatment. - 💡 **Spectrum**: Flucloxacillin is effective against **staphylococci** (including penicillinase-producing strains) but **NOT MRSA**. > **⚠️ Important**: This information is for educational purposes only. Always consult current prescribing information, local guidelines, and clinical judgment before prescribing.