Flucoxacillin

# Flucoxacillin ## Overview - **Classification**: Beta-lactam antibiotic; penicillinase-resistant penicillin - **Mechanism**: Inhibits bacterial cell wall synthesis by binding to penicillin-binding proteins (PBPs), leading to cell lysis. Effective against penicillinase-producing staphylococci. ## Primary Indications 1. **Staphylococcal Infections**: Skin & soft tissue infections (e.g., cellulitis, impetigo, boils). 2. **Bone & Joint Infections**: Osteomyelitis, septic arthritis, typically caused by *Staphylococcus aureus*. 3. **Endocarditis**: Specifically for *Staphylococcus aureus* endocarditis. 4. **Streptococcal Infections**: Where penicillin resistance is suspected or confirmed. ## Adult Dosing ### Standard Dosing **Mild to Moderate Infections (Oral)** - **Dose**: **250 mg** to **500 mg** - **Frequency**: Every **6 hours** - **Route**: Oral (capsule, liquid) **Severe Infections (IV)** - **Dose**: **1 g** to **2 g** - **Frequency**: Every **6 hours** - **Route**: Intravenous (IV) - **Maximum Dose**: Up to **12 g/day** (IV) or **8 g/day** (oral) - **Duration**: Varies by infection type (e.g., 7-14 days for cellulitis, weeks for osteomyelitis). ### Dose Adjustments - **Renal Impairment**: - **CrCl 10-50 mL/min**: No specific adjustment needed for standard doses. - **CrCl <10 mL/min**: Consider **500 mg** every **8-12 hours** or reduce dose. Monitor levels if prolonged high-dose therapy. - **Hepatic Impairment**: Use with caution. Risk of cholestatic jaundice, especially with high doses or prolonged use. Monitor LFTs. - **Elderly Patients**: No specific dose adjustment solely based on age. Adjust based on renal function if impaired. ## Pediatric Dosing ### Neonates (0-28 days) - **Dose**: **25 mg/kg** to **50 mg/kg** - **Frequency**: Every **8-12 hours** (depending on gestational & postnatal age) - **Maximum**: Do not exceed **100 mg/kg/day** (oral) or **200 mg/kg/day** (IV) or adult maximum. - **Special Notes**: Consider more frequent dosing (e.g., Q8H) for severe infections or older neonates (>7 days postnatal age). ### Infants (1-12 months) - **Dose**: **12.5 mg/kg** to **25 mg/kg** - **Frequency**: Every **6 hours** - **Maximum**: Do not exceed **100 mg/kg/day** (oral) or **200 mg/kg/day** (IV) or adult maximum. ### Children (1-12 years) - **Dose**: **12.5 mg/kg** to **25 mg/kg** - **Frequency**: Every **6 hours** - **Maximum**: Do not exceed **100 mg/kg/day** (oral) or **200 mg/kg/day** (IV) or adult maximum. ### Adolescents (13-18 years) - **Dose**: Generally follow **adult dosing** recommendations. - **Maximum**: **Adult maximum dose**. ## Safety Information ### Contraindications - **Absolute**: Hypersensitivity to penicillin antibiotics (e.g., anaphylaxis). - **Absolute**: History of flucloxacillin-associated cholestatic jaundice or hepatic dysfunction. ### Common Adverse Effects - **Common (1-10%)**: Nausea, diarrhea, rash (maculopapular), urticaria. - **Serious but Rare**: - Cholestatic jaundice, hepatitis (can have delayed onset, weeks after discontinuation). - Anaphylaxis/severe hypersensitivity reactions. - Pseudomembranous colitis (C. difficile infection). - Interstitial nephritis. - Neutropenia, thrombocytopenia (rare, usually with prolonged high-dose therapy). ### Key Drug Interactions - **Warfarin**: Increased INR. Flucloxacillin may enhance anticoagulant effect. **Monitor INR closely** during and after co-administration. - **Methotrexate**: Increased methotrexate toxicity (reduced renal clearance). **Avoid concomitant use** or monitor methotrexate levels closely. - **Oral Contraceptives**: Potential reduced efficacy (historical concern, less evidence for modern low-dose OCs). Counsel on alternative contraception. - **Allopurinol**: Increased risk of skin rash with co-administration. ## Monitoring & Follow-up - **Before Treatment**: Baseline LFTs (if pre-existing hepatic disease), renal function (especially in elderly or renally impaired). - **During Treatment**: - Monitor for signs of hypersensitivity reactions (rash, itching, dyspnea). - Liver function tests (LFTs) if prolonged therapy, high doses, or signs of hepatic dysfunction. - Renal function tests if prolonged therapy or pre-existing renal impairment. - Full blood count (FBC) if prolonged high-dose therapy (risk of neutropenia). - **Clinical Signs**: Monitor for resolution of infection symptoms. Watch for delayed-onset cholestatic jaundice (can occur up to 2 months post-treatment). ## Clinical Pearls - 💡 **Administration**: For optimal absorption, administer oral flucloxacillin on an **empty stomach** (at least 1 hour before or 2 hours after food). - 💡 **Hepatic Risk**: Counsel patients about the risk of cholestatic jaundice, even **weeks after stopping** the drug. Report persistent nausea, vomiting, dark urine, or yellow skin/eyes. - 💡 **MSSA Coverage**: Flucloxacillin is effective against Methicillin-Sensitive *Staphylococcus aureus* (MSSA) but **not** Methicillin-Resistant *Staphylococcus aureus* (MRSA). - 💡 **Formulation**: Oral liquid suspensions require refrigeration and shaking before use. > **⚠️ Important**: This information is for educational purposes only. Always consult current prescribing information, local guidelines, and clinical judgment before prescribing.