What is the recommended dose of Cephalexin (cephalexin) for a patient with strep throat, assuming no known allergies to penicillin or other antibiotics and no underlying medical conditions?

Cephalexin Dosing for Strep Throat

For adults with strep throat, cephalexin 500 mg orally every 12 hours for 10 days is the recommended dose, and this regimen is specifically FDA-approved for streptococcal pharyngitis. 1

FDA-Approved Dosing Regimen

• The FDA label explicitly states that for streptococcal pharyngitis, 500 mg may be administered every 12 hours in adults, which is more convenient than the standard four-times-daily dosing used for other infections 1
• The full 10-day course is mandatory to achieve maximal pharyngeal eradication of Group A Streptococcus and prevent acute rheumatic fever, even if symptoms resolve in 3-4 days 2, 3
• The adult dosage range is 1 to 4 grams daily in divided doses, but the twice-daily 500 mg regimen (total 1 gram/day) is sufficient for uncomplicated streptococcal pharyngitis 1

Pediatric Dosing

• For children over 1 year of age with streptococcal pharyngitis, the recommended dose is 25-50 mg/kg/day divided every 12 hours 1, 4
• The total daily dose may be divided and administered twice daily specifically for streptococcal pharyngitis, improving compliance compared to four-times-daily dosing 1
• For β-hemolytic streptococcal infections, a therapeutic dosage must be administered for at least 10 days 1

When Cephalexin Should Be Used

Cephalexin is appropriate for patients with non-immediate (non-anaphylactic) penicillin allergy, as first-generation cephalosporins are the preferred first-line alternatives with strong, high-quality evidence 2, 3

• The cross-reactivity risk is only 0.1% in patients with non-severe, delayed penicillin reactions 2
• Do not use cephalexin in patients with immediate/anaphylactic penicillin reactions (anaphylaxis, angioedema, respiratory distress, or urticaria within 1 hour) due to up to 10% cross-reactivity risk 2
• For immediate/anaphylactic penicillin allergy, clindamycin 300 mg three times daily for 10 days is the preferred alternative 2, 3

Evidence Supporting Cephalexin Efficacy

• Cephalexin demonstrates cure rates of 90% or higher for streptococcal pharyngitis, comparable to penicillin 5
• A randomized, double-blind study of 525 children showed cephalexin had a 10% combined treatment failure rate versus 19% for penicillin, making it more effective than penicillin in eliminating Group A Streptococcus 5
• The twice-daily dosing enhances medication compliance compared to four-times-daily regimens 6

Critical Pitfalls to Avoid

• Never shorten the course below 10 days—this dramatically increases treatment failure rates and rheumatic fever risk, even if symptoms resolve earlier 2, 3
• Do not prescribe broad-spectrum cephalosporins (cefdinir, cefixime, cefpodoxime) when cephalexin is appropriate, as they are more expensive and more likely to select for antibiotic-resistant flora 2
• Confirm the type of penicillin allergy before prescribing—assuming all penicillin-allergic patients cannot receive cephalosporins is incorrect; only those with immediate/anaphylactic reactions should avoid them 2

Adjunctive Symptomatic Treatment

• Acetaminophen or NSAIDs (such as ibuprofen) should be offered for moderate to severe symptoms or high fever 3
• Aspirin must be avoided in children due to Reye syndrome risk 3
• Corticosteroids are not recommended as adjunctive therapy 3