What is the strongest oral (PO) dose of cephalexin?

Maximum Oral Dose of Cephalexin

The maximum oral dose of cephalexin for adults is 4 grams per day in divided doses. 1

Adult Dosing Guidelines

The FDA-approved dosing for cephalexin provides clear parameters:

• Standard adult dose: 250 mg every 6 hours
• For certain infections (streptococcal pharyngitis, skin/skin structure infections, uncomplicated cystitis): 500 mg every 12 hours
• Daily dosage range: 1-4 grams divided throughout the day
• If doses greater than 4 g/day are required, parenteral (IV) cephalosporins should be considered 1

Specific Clinical Scenarios

Different infections may require different dosing within this maximum range:

• For methicillin-susceptible Staphylococcus aureus skin infections: 500 mg four times daily 2
• For skin and soft tissue infections: 75-100 mg/kg/day in 3-4 divided doses 2

Pediatric Dosing

For pediatric patients, dosing is weight-based:

• Standard recommended daily dosage: 25-50 mg/kg in divided doses
• For otitis media: 75-100 mg/kg/day in 4 divided doses
• For streptococcal pharyngitis: Total daily dose may be divided and administered every 12 hours 1

Special Considerations

Renal Impairment

• Patients with creatinine clearance less than 30 ml/min require dose reduction proportional to their reduced renal function 3
• Cephalexin is rapidly cleared by the kidneys with 70-100% of the dose found in urine 6-8 hours after administration 3

Efficacy of Different Dosing Regimens

• Twice-daily dosing (500 mg or 1 g) has been shown to be effective for respiratory and soft tissue infections, with the 1 g twice daily dose potentially providing more rapid response 4

Pharmacokinetic Factors

• Cephalexin is not absorbed from the stomach but is totally and rapidly absorbed in the upper intestine
• It does not penetrate into host tissue cells, which contributes to its relatively low incidence of side effects 3

Common Pitfalls to Avoid

1. Exceeding maximum daily dose: Never exceed 4 g/day orally; consider parenteral therapy if higher doses are needed
2. Inadequate dosing for severe infections: For severe infections, use the higher end of the dosing range
3. Failure to adjust for renal impairment: Dose reduction is necessary for patients with impaired renal function
4. Inappropriate dosing frequency: While twice-daily dosing may be effective for some infections, more frequent dosing (every 6 hours) may be needed for others

Remember that while 4 grams per day is the maximum oral dose, the appropriate dose should be based on the specific infection being treated, the severity of infection, and patient factors such as renal function.