What is the recommended dose of cephalexin (cephalosporin antibiotic)?

From the Guidelines

Cephalexin should be dosed at 20 mg per kg per dose twice daily (maximum = 500 mg per dose) for 10 days in patients with penicillin allergy, as recommended by the IDSA guideline for managing group A streptococcal pharyngitis 1. The dosage of cephalexin can vary depending on the type of infection being treated.

• For skin and soft tissue infections, a dose of 250-500 mg orally every 6 hours, or 500-1000 mg every 12 hours is common in adults with normal kidney function 1.
• For children, the usual dose is 25-50 mg/kg/day divided into 2-4 equal doses 1. The specific dosage depends on the severity of infection, with more serious infections requiring higher doses.
• Patients with reduced kidney function require dose adjustments, typically with extended intervals between doses. It's essential to complete the full course of treatment even if symptoms improve before finishing, as this helps prevent the development of antibiotic-resistant bacteria. Cephalexin works by inhibiting bacterial cell wall synthesis, making it effective against many gram-positive bacteria and some gram-negative organisms. Common side effects include gastrointestinal disturbances, and patients with penicillin allergies may have cross-reactivity. However, the recommended dose of 20 mg per kg per dose twice daily (maximum = 500 mg per dose) for 10 days in patients with penicillin allergy is the most appropriate choice, as it is based on the strongest and most recent evidence from the IDSA guideline 1.

From the FDA Drug Label

Adults The adult dosage ranges from 1 to 4 g daily in divided doses. The usual adult dose is 250 mg every 6 hours For the following infections, a dosage of 500 mg may be administered every 12 hours: Pediatric Patients The usual recommended daily dosage for pediatric patients is 25 to 50 mg/kg in divided doses

The recommended dose of cephalexin is:

• For adults: 250 mg every 6 hours or 500 mg every 12 hours, with a total daily dose ranging from 1 to 4 g
• For pediatric patients: 25 to 50 mg/kg in divided doses, with the total daily dose divided and administered every 12 hours 2

From the Research

Cephalexin Dosing Regimens

• The optimal dosing regimen for cephalexin varies depending on the type of infection being treated, with studies suggesting different dosing frequencies for urinary tract infections (UTIs) and bone and joint infections 3, 4, 5, 6, 7.
• For UTIs, a study found that twice-daily cephalexin dosing is as effective as four-times-daily dosing, with no significant difference in treatment failure rates between the two groups 4.
• Another study compared twice-daily and four-times-daily cephalexin dosing for UTIs diagnosed in the emergency department, finding no statistically significant difference in treatment failure rates between the two groups 7.
• For bone and joint infections in children, a study found that a high-dose cephalexin regimen of 45 mg/kg (maximum 1.5 g) three times daily is effective and well-tolerated 5.
• A population pharmacokinetic model developed for cephalexin in children suggested twice-daily and thrice-daily dosing regimens for methicillin-susceptible Staphylococcus aureus (MSSA) infections, with required doses ranging from 15-45 mg/kg depending on the minimum inhibitory concentration of the bacteria 6.

Dosing Frequencies and Treatment Outcomes

• Twice-daily cephalexin dosing has been shown to be effective for UTIs, with treatment failure rates ranging from 12.7% to 18.7% 4, 7.
• Four-times-daily cephalexin dosing has also been shown to be effective for UTIs, with treatment failure rates ranging from 15.0% to 17.0% 4, 7.
• Three-times-daily cephalexin dosing has been shown to be effective for bone and joint infections in children, with a cure rate of 99% and minimal adverse events 5.

Special Considerations

• Cephalexin dosing regimens may need to be adjusted based on the severity of the infection, the patient's age and weight, and the presence of any underlying medical conditions 3, 5, 6.
• The choice of cephalexin dosing regimen should take into account the potential for improved treatment adherence and reduced medication burden with less frequent dosing regimens 4, 7.