What is a suitable treatment for strep throat in a patient with an allergy to penicillin and cephalexin (Keflex)?

Treatment of Strep Throat in Patients Allergic to Both Penicillin and Cephalexin

For a patient with strep throat who is allergic to both penicillin and cephalexin (Keflex), clindamycin 300 mg orally three times daily for 10 days is the optimal treatment choice. 1

Why Clindamycin is the Best Option

Since your patient has documented allergies to both penicillin and a first-generation cephalosporin (cephalexin), this indicates either an immediate/anaphylactic penicillin allergy or a history suggesting you should avoid all beta-lactam antibiotics. 1

Clindamycin is specifically recommended by the Infectious Diseases Society of America as the preferred alternative for patients with immediate/anaphylactic penicillin reactions who cannot use cephalosporins. 1 The evidence supporting this recommendation is strong with moderate-quality data. 1

Key Advantages of Clindamycin:

• Extremely low resistance: Only approximately 1% resistance among Group A Streptococcus isolates in the United States 1
• Superior efficacy: Demonstrates high efficacy in eradicating streptococci, even in chronic carriers who have failed other treatments 1
• Proven track record: Strong, moderate-quality evidence supports its use in penicillin-allergic patients 1

Dosing Requirements

The full 10-day course is absolutely essential - do not shorten this even if symptoms resolve in 3-4 days. 1 The primary goal is not just symptom relief but prevention of acute rheumatic fever, which requires complete bacterial eradication. 1

• Adult dosing: 300 mg orally three times daily for 10 days 1
• Pediatric dosing: 7 mg/kg per dose three times daily (maximum 300 mg per dose) for 10 days 1

Alternative Option: Azithromycin (Second-Line)

If clindamycin cannot be used (e.g., patient intolerance, drug interactions, or allergy), azithromycin is an acceptable alternative:

• Adult dosing: 500 mg on day 1, then 250 mg daily for days 2-5 1
• Pediatric dosing: 12 mg/kg once daily (maximum 500 mg) for 5 days 1, 2

Important Caveats About Azithromycin:

• Higher resistance rates: Macrolide resistance is 5-8% in the United States and varies geographically 1
• Less reliable: Clindamycin is more reliable due to its 1% resistance rate versus azithromycin's 5-8% 1
• No rheumatic fever data: The FDA label explicitly states that "data establishing efficacy of azithromycin in subsequent prevention of rheumatic fever are not available" 2
• Requires susceptibility testing: The FDA recommends susceptibility tests should be performed when treating with azithromycin because some strains are resistant 2

Critical Pitfalls to Avoid

Do NOT Use These Antibiotics:

• Trimethoprim-sulfamethoxazole (Bactrim): Absolutely contraindicated - does not eradicate Group A Streptococcus and has 50% resistance rates 1
• Tetracyclines: High prevalence of resistant strains 1
• Older fluoroquinolones (ciprofloxacin): Limited activity against Group A Streptococcus 1

Do NOT Shorten the Course:

Shortening the antibiotic course below 10 days (except azithromycin's 5-day regimen) dramatically increases treatment failure rates and risk of acute rheumatic fever. 1 Even though symptoms typically resolve within 3-4 days without treatment, full course completion is essential for preventing complications. 1

Adjunctive Symptomatic Treatment

• For pain/fever: Acetaminophen or NSAIDs (such as ibuprofen) for moderate to severe symptoms 1
• Avoid aspirin in children: Risk of Reye syndrome 1
• Do NOT use corticosteroids: Not recommended as adjunctive therapy 1

When to Consider Chronic Carrier Status

If this patient has recurrent "strep throat" despite appropriate treatment, consider that they may be a chronic carrier experiencing repeated viral pharyngitis rather than true recurrent streptococcal infections. 1 Chronic carriers generally do not require antimicrobial therapy, as they are unlikely to spread GAS pharyngitis and are at little risk for complications. 1