Clinical beta
FMBM is currently in clinical beta. Content is for professional review/testing and must not replace local protocols, senior clinical judgment, or official prescribing references.
Drug Monograph
Cloxacillin
Penicillinase-resistant antistaphylococcal penicillin
Indication
MSSA skin/soft tissue infection β’ MSSA bone/joint infection β’ MSSA pneumonia β’ MSSA bacteremia/endocarditis
INDICATIONS (CORE USE)
MSSA skin/soft tissue infection β’ MSSA bone/joint infection β’ MSSA pneumonia β’ MSSA bacteremia/endocarditis
ADULT DOSE (STANDARD)
Oral: 500 mg PO q6h IV: 1β2 g IV q4β6h
MAX DOSE
Max: 2 g IV q4h β total 8β12 g/day (adjust in major renal impairment per labeling)
Route
PO, IV, IM
PEDIATRIC DOSE
25β50 mg/kg/dose IV/PO q6h β Severe MSSA: 50 mg/kg/dose IV q6h β Neonates: 25β50 mg/kg IV q8β12h per age/renal function
Must-not-miss safety points
Major warning
- Hypersensitivity (anaphylaxis risk) - No MRSA coverage β DO NOT use if MRSA suspected or confirmed - Not active against MRSA β confirm MSSA before use in severe infection - Delayed cholestatic hepatitis may occur weeks after stopping therapy β monitor LFTs if symptoms - High sodium load (IV) β caution in heart failure, CKD, and ICU patients - Risk increases with prolonged use (>2 weeks) and older age - High-dose IV: electrolyte disturbance, AKI, neurotoxicity risk - PO absorption reduced by food β empty stomach preferred - Gram-negative/polymicrobial infection requires added coverage β not reliable monotherapy
USE IF: MSSA skin/soft tissue infection; MSSA bone/joint infection; MSSA pneumonia; MSSA bacteremia/endocarditis when a penicillinase-resistant antistaphylococcal Ξ²-lactam is appropriate. AVOID IF: MRSA (or high MRSA likelihood without adequate coverage); gram-negative or polymicrobial infection without added agents; prior cloxacillin/flucloxacillin cholestatic hepatitis. Isoxazolyl penicillinβmatch to confirmed or high-probability MSSA and monitor liver function with prolonged therapy.
ADULT DOSE
PO: 500 mg q6h IV: 1β2 g q4β6h Adult PO: Mildβmoderate MSSA SSTI: 500 mg q6h Severe but stable step-down: 1 g q6h Bone/joint step-down: 500 mgβ1 g q6h Adult IV: Severe MSSA: 1β2 g IV q4β6h Pneumonia/bacteremia/endocarditis: often 2 g IV q4h
PEDIATRIC DOSE
25β50 mg/kg/dose IV/PO q6h. Severe MSSA infection: 50 mg/kg/dose IV q6h. Neonates: 25β50 mg/kg IV q8β12h per age/renal function (per neonatal reference).
MAX DOSE
Max adult dose: 2 g IV q4h β total daily 8β12 g/day β titrate in major renal impairment per product monograph.
Practical Note
- Renal adjustment usually not required β only modify in severe renal impairment (CrCl <30 mL/min or dialysis: reduce dose or extend interval, e.g., 1β2 g q8β12h) - Infective endocarditis requires high-dose IV therapy β ensure guideline-level dosing (e.g., 2 g IV q4β6h) - Hepatic: no numeric algorithm; avoid prolonged/high-dose in chronic liver disease when possible - PO: best on empty stomach (1 h before or 2 h after food) - Switch IV β PO once clinically stable and improving
Clinical warnings
Adverse effects
Pediatrics
25β50 mg/kg/dose IV/PO q6h β Severe MSSA: 50 mg/kg/dose IV q6h β Neonates: 25β50 mg/kg IV q8β12h per age/renal function
Pregnancy
Generally safe in pregnancy when indicated; monitor LFTs with prolonged courses. Breastfeeding usually compatible β observe infant for diarrhea, rash, or candidiasis. Pregnancy: Generally safe; monitor LFTs if prolonged therapy.
Lactation
Compatible β monitor infant for diarrhea, rash, candidiasis.
Renal impairment
Mildβmoderate may tolerate standard dosing. Severe impairment or RRT: reduce dose or extend interval; monitor neurotoxicity and AKI with high-dose IV.
Hepatic impairment
No formal dose reduction; use great caution. Baseline and serial LFTs for prolonged courses.
Elderly
Higher cholestatic hepatitis risk; monitor LFTs and renal function closely.
Give on empty stomach (1 h before or 2 h after food). PO: capsules/suspension. IV or IM: sodium salt β intermittent IV 1β2 g over 30β60 min per protocol; continuous infusion may be used for severe MSSA infection. IM: deep IM if IV unavailable. Prefer IV initially for serious infection, then step down to PO when stable.
Clinical Picture
No exact threshold; risk rises with very high IV doses and severe renal impairment. Features: agitation, confusion, myoclonus, seizures; rising creatinine; reduced urine output; delayed cholestatic hepatitis.
Immediate Actions
- Stop cloxacillin immediately - Supportive care
Antidote
No specific antidote β supportive care
Decontamination
Massive oral ingestion β contact poison center; charcoal rarely indicated.
Escalation
Benzodiazepines for seizures; check renal function, electrolytes, LFTs, INR; stop drug if hepatitis suspected β monitor LFTs/coagulation; consider dialysis for severe AKI or neurotoxicity per nephrology.
Common mistakes, resistance logic, and bedside traps
FIRST LINE: Narrow-spectrum anti-MSSA Ξ²-lactam for staph skin, bone, joint, lung, and bloodstream infection. DOSE β Oral: 500 mg PO q6h; IV: 1β2 g IV q4β6h. MAX β 2 g IV q4h; 8β12 g/day total. AVOID β MRSA; severe liver toxicity history from isoxazolyl penicillins; high-dose in major renal impairment without adjustment. ANTIDOTE β None.
- Max adult dose: 2 g IV q4h - Delayed cholestatic hepatitis can occur during therapy or weeks later - Stop immediately if jaundice, pruritus, dark urine, pale stool, or major LFT rise - Not active against MRSA - High-dose IV: neurotoxicity, nephrotoxicity, sodium load, electrolyte issues - Best absorbed on empty stomach - Deep MSSA infection usually needs full-dose IV first, not low-dose oral alone
Use only when MSSA is suspected or confirmed and MRSA is unlikely. Do not use alone for polymicrobial diabetic foot or mixed wound infection unless additional coverage is added. For deep MSSA infection, oral therapy alone is usually inadequate initially. In patients >55 years, with liver disease, or on >14-day courses, liver monitoring is critical. New jaundice after cloxacillin = drug-related until proven otherwise. 3 AM check: MSSA confirmed? Renal function okay? LFTs current? IV-to-PO plan documented?
- Oral bioavailability ~50β70% - Absorption reduced by food - Partial hepatic metabolism - Mainly renal elimination with some biliary excretion - Half-life ~0.5β1 h - Prolonged half-life in renal impairment, neonates, and elderly
Penicillinase-resistant isoxazolyl penicillin. Binds penicillin-binding proteins and inhibits peptidoglycan cross-linking. Active against MSSA and some streptococci. Not active against MRSA or most gram-negatives.
Saudi Arabia
Cloxacillin (generic), CLOXACILLIN-ELSaad
Global
Cloxacillin (manufacturer generic), Cloxacillin sodium (regional generics), Cloxacillin sodium (generic), Local cloxacillin sodium products
Common trade names are curated examples only β formulations and availability vary. Verify the exact product name with your local pharmacy and national regulator before prescribing or dispensing.
Saudi Arabia
International