Cephalexin
Cephalexin
Keflex, Daxbia, Panixine; mostly prescribed generically
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Summary
Common uses
Uncomplicated skin and soft-tissue infections0, Streptococcal pharyngitis0, Uncomplicated UTI0, Surgical prophylaxis (selected procedures)0, Dental procedural prophylaxis in penicillin allergy (non-anaphylactic)0
Pharmacy
Starting dose
500 mg PO every 6 hours, or 250 mg every 6 hours for mild infections
Preparations
250 mg, 500 mg, 750 mg capsules; 250 mg/5 mL, 125 mg/5 mL suspension; tablets
US FDA Max
4 g/d
Pharmacology
Routes
Oral
Onset
Hours
Duration
6-8 hours
Half-life
~1 hour[1]
Bioavailability
90% (oral; food delays but does not reduce absorption)[1]
Pregnancy
Generally considered safe; widely used.[citation needed]
Legal status
Rx-only in US
Purported mechanism
Cephalexin binds penicillin-binding proteins (PBPs) in the bacterial cell wall and inhibits transpeptidation of peptidoglycan cross-links; loss of structural integrity causes osmotic lysis of growing organisms.0 Spectrum: gram-positive cocci (excluding MRSA and enterococci) and some gram-negatives (E. coli, Klebsiella, Proteus mirabilis). True cross-reactivity with penicillin is uncommon (<3%) but the historical anaphylaxis warning still drives clinical avoidance in severe penicillin allergy[1].
References
- ↑ 1.0 1.1 1.2 FDA Prescribing Information, Keflex (cephalexin), Pragma Pharmaceuticals, current revision. https://www.accessdata.fda.gov/drugsatfda_docs/label/2006/050405s094,050674s006lbl.pdf