What is the recommended dose of cephalexin (cephalosporin antibiotic) for adults and children?

Recommended Cephalexin Dosing for Adults and Children

The recommended dose of cephalexin for adults is 250-500 mg every 6 hours (1-4 g daily in divided doses), while for children the standard dosage is 25-50 mg/kg/day divided into 4 doses for most infections, with higher doses of 75-100 mg/kg/day in 4 divided doses recommended for more severe infections such as otitis media. 1, 2

Adult Dosing

• Standard adult dosing is 250 mg every 6 hours (1 g daily) for most infections 1
• For more severe infections, 500 mg every 6 hours (2 g daily) is recommended 1, 2
• For certain infections like streptococcal pharyngitis, skin and skin structure infections, and uncomplicated cystitis in patients over 15 years of age, 500 mg every 12 hours may be administered 1
• The maximum daily dose for adults should not exceed 4 g; if higher doses are required, parenteral cephalosporins should be considered 1
• For skin and soft tissue infections, particularly for methicillin-susceptible Staphylococcus aureus (MSSA), 500 mg four times daily is recommended 3, 2

Pediatric Dosing

• The usual recommended daily dosage for pediatric patients is 25-50 mg/kg divided into 4 doses 1
• For streptococcal pharyngitis in patients over 1 year of age and for skin and skin structure infections, the total daily dose may be divided and administered every 12 hours 1
• For otitis media, clinical studies have shown that a higher dosage of 75-100 mg/kg/day in 4 divided doses is required 1, 2
• For MSSA infections in children, 75-100 mg/kg/day in 3-4 divided doses is recommended 2
• For β-hemolytic streptococcal infections, cephalexin should be administered for at least 10 days 1

Infection-Specific Considerations

• For skin and soft tissue infections: 500 mg four times daily for adults and 25-50 mg/kg/day in 4 divided doses for children with mild infections 3, 2
• For respiratory tract infections: 500 mg four times daily for adults and 25-50 mg/kg/day in 4 divided doses for children 2
• For urinary tract infections: Recent evidence suggests that 500 mg twice daily may be as effective as 500 mg four times daily for uncomplicated UTIs in females 4
• For MSSA infections: 500 mg four times daily for adults; for children, 75-100 mg/kg/day in 3-4 divided doses 2

Special Considerations

• Patients with renal impairment (creatinine clearance less than 30 ml/min) require dose reduction proportional to the reduced kidney function 5
• Duration of therapy is typically 7-10 days for most infections, depending on clinical response 2
• Cephalexin suspension should be prepared at the time of dispensing and stored in the refrigerator; it may be kept for 14 days without significant loss of potency 1
• Children may require higher doses per kilogram than adults due to their greater body water turnover 5
• Cephalexin is well absorbed from the upper intestine but not from the stomach, with 70-100% of the dose found in the urine 6-8 hours after administration 5

Common Pitfalls and Caveats

• Cephalexin should not be used as first-line therapy for MRSA infections despite some clinical studies showing response, as it does not have clinically relevant in vitro activity against MRSA 6
• For severe infections or those caused by less susceptible organisms, larger doses may be needed 1
• Cephalexin has limited activity against Pasteurella multocida (commonly found in animal bites) and anaerobes 3
• When treating β-hemolytic streptococcal infections, ensure the full 10-day course is completed to prevent rheumatic fever 1
• Twice-daily dosing may improve patient adherence compared to four-times-daily dosing, particularly for uncomplicated UTIs 4