Recommended Dosage and Treatment Duration for Cephalexin
For adults, the standard dosage of cephalexin is 250 mg every 6 hours or 500 mg every 12 hours for most infections, with a total daily dose ranging from 1 to 4 grams divided throughout the day. 1
Adult Dosing
- For uncomplicated skin and soft tissue infections: 500 mg three times daily or 500 mg four times daily for more severe infections 2
- For streptococcal pharyngitis and uncomplicated cystitis: 500 mg every 12 hours 1
- For urinary tract infections: Treatment should continue for 7-14 days 1
- Recent evidence suggests that twice-daily dosing (500 mg BID) is as effective as four-times-daily dosing for uncomplicated urinary tract infections 3
Pediatric Dosing
- The recommended daily dosage for pediatric patients is 25-50 mg/kg divided into equal doses throughout the day 1
- For streptococcal pharyngitis in children over 1 year and skin infections, the total daily dose may be administered every 12 hours 1
- For otitis media, higher dosages of 75-100 mg/kg/day in 4 divided doses are required 1
- For β-hemolytic streptococcal infections, treatment should continue for at least 10 days 1
Treatment Duration
- For skin and soft tissue infections: Typically 7 days, depending on clinical response 2
- For streptococcal pharyngitis: At least 10 days 1
- For urinary tract infections: 7-14 days 1
- If infection has not improved within 5 days, treatment should be extended 2
Special Considerations
- For more severe infections or those caused by less susceptible organisms, larger doses may be needed 1
- If daily doses greater than 4 g are required, parenteral cephalosporins should be considered 1
- For methicillin-susceptible Staphylococcus aureus (MSSA) infections: 500 mg four times daily 4
- Patients with creatinine clearance less than 30 ml/min require dose reduction proportional to reduced kidney function 5
Common Pitfalls and Caveats
- Cephalexin is not effective against MRSA; if MRSA is suspected, alternative agents should be considered 2
- Patients with a history of immediate hypersensitivity to penicillin should use cephalexin with caution due to potential cross-reactivity 2
- Cephalexin has limited activity against Pasteurella multocida and anaerobes 2
- For simple skin abrasions without signs of significant infection, topical antimicrobial agents may be sufficient 2
- If systemic signs of infection develop during treatment, consider broadening antimicrobial coverage 2