C. diff Risk


Oral Bioavailability


Approximate Cost


CrCl Less Than 10 mL/minGive 50% of dose BID

CrCl 10-24 mL/minReduce dosing frequency to BID

CrCl 25-49 mL/minReduce dosing frequency to TID

CrCl Greater Than 50 mL/minGive usual dose

250-1000mg PO QID

General Information

Common Usage

  •  Uncomplicated skin and soft tissue infection

  •  MSSA infections

  • Uncomplicated Cystitis

Adverse Effects

  •  Allergy/rash (immediate or delayed)

  • Dermatologic reactions including erythema multiforme, Stevens-Johnson Syndrome (rare) and Toxic Epidermal Necrolysis (rare)

  •  Positive Coombs

  •  Cytopenias

  •  Eosinophilia

  • CNS effects including agitation, hallucination, confusion, fatigue, headache, dizziness

  •  Hepatic & renal laboratory abnormalities

  • GI disturbances (diarrhea, nausea)

  • Arthralgia, arthropathy

  • Interstitial Nephritis (rare)

Major Interactions

Increases metformin levels

May enhance anticoagulant effect of vitamin K antagonists (including warfarin)

May decrease the levels/effects of: BCG (intravesical or vaccine); Cholera vaccine; Typhoid vaccine; Estriol, Sodium Picosulfate, Lactobacillus.

Some vitamins and minerals may reduce absorption/levels of cephalexin


Antimicrobial class: First Generation Cephalosporin.

Pregnancy category: B

Average serum half life: 0.5-1.2 hr (longer with renal impairment)

Biliary penetration: Moderate

CSF penetration: Poor

Lung penetration: Moderate

Urine penetration: Therapeutic