Infectious Disease Compendium

Cephalexin (Keflex®)


CrCl Formula

CrCl > 80: 250 mg - 1000 mg q 6 h po.

CrCl 80-50: 250 mg - 1000 mg q 6 h po.

CrCl 50-10: 250 mg - 1000 mg q 8-12 h po.

CrCl < 10: 250 mg - 1000 mg q 24- 48 h po.

Hemodialysis: 250 mg - 1000 mg after dialysis.

Peritoneal dialysis: na.

Important side effects

Important drug interactions

Concomitant cephalexin and cholestyramine reduces cephalexin absorption.

Rants and Screeds


As you double the oral dose, you double the serum levels. Many patients tolerate 1 gm po qid (peak of 32 ug/ml) and may remove the need for iv rx of mild to moderate cellulitis.

Treatment of choice

Use for

Streptococci of all types and methicillin susceptible S. aureus. Bronchitis, Cellulitis, Cystic fibrosis, dental prophylaxis, Diverticulosis/itis, Lyme Disease, Osteomyelitis, Otitis media, Peritonitis, Pharyngitis, Pneumonia, Prostatitis, Sinusitis, UTI.

Don't use for


First generation cephalosporin.