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

Cephalexin Dosing Recommendations

For adults, cephalexin should be dosed at 500 mg four times daily (every 6 hours) for most infections, while pediatric patients require 25-50 mg/kg/day divided into 4 doses for mild-to-moderate infections or 75-100 mg/kg/day divided into 3-4 doses for methicillin-susceptible Staphylococcus aureus (MSSA) infections. 1

Adult Dosing

Standard dosing for most infections:

• 500 mg orally every 6 hours (four times daily) is the recommended dose for most bacterial infections in adults with normal renal function 2, 1
• For mild-to-moderate infections, 250-500 mg every 6 hours may be adequate 1
• The total daily dose ranges from 1-4 grams divided throughout the day 1

Infection-specific considerations:

• Skin and soft tissue infections (including MSSA): 500 mg four times daily 3, 2
• Streptococcal pharyngitis: 500 mg every 12 hours is acceptable 1
• Uncomplicated cystitis (patients >15 years): 500 mg every 12 hours for 7-14 days 1
• Mastitis in lactating women: 500 mg every 6 hours 2

Important caveat: If daily doses exceeding 4 grams are required, parenteral cephalosporins should be considered instead 1

Pediatric Dosing

Standard pediatric dosing:

• Mild-to-moderate infections: 25-50 mg/kg/day divided into 4 doses (every 6 hours) 1
• MSSA infections (including pneumonia): 75-100 mg/kg/day divided into 3-4 doses 3, 2
• Otitis media: 75-100 mg/kg/day in 4 divided doses is required for adequate treatment 1

Alternative twice-daily dosing:

• For streptococcal pharyngitis and skin/soft tissue infections in patients >1 year: the total daily dose may be divided and given every 12 hours 1

Severe infections:

• The dosage may be doubled from the standard recommendation 1

Critical Clinical Considerations

Duration of therapy:

• Most infections: 7-10 days depending on clinical response 2
• β-hemolytic streptococcal infections: minimum 10 days of treatment 1

Renal impairment:

• Patients with creatinine clearance <30 mL/min require dose reduction proportional to their reduced renal function 4
• Cephalexin is 70-100% renally excreted within 6-8 hours 4

When to consider alternatives:

• If MRSA is suspected or confirmed, switch to trimethoprim-sulfamethoxazole or clindamycin, as cephalexin lacks reliable MRSA coverage 2
• Severe penicillin allergy (IgE-mediated): avoid cephalexin due to cross-reactivity risk 2

Practical administration:

• Suspension must be refrigerated after mixing and remains stable for 14 days 1
• Absorption occurs in the upper intestine, not the stomach 4
• Food delays but does not prevent absorption 5