Recommended Dosage of Cephalexin (Keflex)
The recommended adult dose of cephalexin (Keflex) is 250-500 mg orally every 6 hours, with a total daily dosage ranging from 1 to 4 grams divided throughout the day. 1
Adult Dosing Guidelines
Standard adult dose: 250 mg every 6 hours
For specific infections: 500 mg every 12 hours can be used for:
- Streptococcal pharyngitis
- Skin and skin structure infections
- Uncomplicated cystitis in patients over 15 years of age
Severe infections: May require higher doses, up to 4 g daily
Alternative dosing for skin infections: 500 mg 3-4 times daily for 5-6 days 2
Pediatric Dosing Guidelines
Standard pediatric dose: 25-50 mg/kg/day divided into equal doses 1
Dosing frequency options:
- Four times daily (traditional regimen)
- Twice daily or three times daily for streptococcal pharyngitis and skin/soft tissue infections in children over 1 year 1
Severe infections: Dosage may be doubled
Otitis media: 75-100 mg/kg/day in 4 divided doses 1
Streptococcal infections: Treatment should continue for at least 10 days 1
Special Considerations
Renal Impairment
- Patients with creatinine clearance <30 mL/min require dose reduction proportional to decreased renal function 3
- Cephalexin is rapidly cleared by the kidneys with 70-100% of the dose found in urine within 6-8 hours 3
Duration of Therapy
Practical Considerations
- Cephalexin is not effective against MRSA; alternative agents like TMP-SMX, doxycycline, or clindamycin should be used if MRSA is suspected 2
- Clinical improvement should be evident within 48-72 hours; if not, reassessment and possible antibiotic change is warranted 2
- Bacterial cultures should be obtained to guide targeted antibiotic therapy when appropriate 2
Simplified Dosing Options
Recent research suggests that less frequent dosing may be effective for certain indications:
- For adults with urinary tract infections, 1 g twice daily has shown similar efficacy to four-times-daily dosing 4
- For children with MSSA infections, twice-daily dosing at 22-45 mg/kg (for MIC 1-2 mg/L) or 80 mg/kg (for MIC 4 mg/L) may be effective 5
- For children, thrice-daily dosing at 15-25 mg/kg (for MIC 1-2 mg/L) or 45 mg/kg (for MIC 4 mg/L) may be effective 5
These simplified regimens may improve medication adherence while maintaining efficacy, though the FDA-approved dosing remains the standard recommendation.