What medication should be prescribed for a 32-year-old adult male with acute streptococcal pharyngitis who has a penicillin allergy, and what are the indications for treating streptococcal pharyngitis?

Antibiotic Choice for Strep Throat with Penicillin Allergy

For a 32-year-old male with confirmed streptococcal pharyngitis and penicillin allergy, prescribe a 10-day course of a narrow-spectrum oral cephalosporin (cephalexin or cefadroxil) as first-line therapy, unless the patient has a history of anaphylactic-type reaction to penicillin, in which case use clindamycin or azithromycin (though azithromycin has inferior efficacy). 1

Antibiotic Selection Algorithm for PCN-Allergic Patients

First-Line: Narrow-Spectrum Cephalosporins (10 days)

• Cephalexin or cefadroxil are the preferred agents 1
• These are superior to penicillin for GAS eradication and are much less expensive than broad-spectrum alternatives
• Critical caveat: Do NOT use if the patient has immediate (anaphylactic-type) hypersensitivity to penicillin, as up to 10% of penicillin-allergic persons are also allergic to cephalosporins 1

Second-Line Options:

If anaphylactic penicillin allergy:

• Clindamycin - Excellent choice with only 1% GAS resistance in the United States 1
• Macrolides/Azalides - Reasonable but problematic:
  • Azithromycin (5 days) or clarithromycin/erythromycin (10 days) 1
  • Major concern: Macrolide resistance rates are 5-8% in most U.S. areas 1, and recent evidence shows azithromycin has inferior efficacy with reduced early bacterial eradication (OR 0.53), reduced late eradication (OR 0.38), higher recurrence rates, and increased adverse events compared to penicillin 2
  • Avoid erythromycin due to substantially higher gastrointestinal side effects 1

Agents to AVOID:

• Broad-spectrum cephalosporins (cefaclor, cefuroxime, cefixime, cefdinir, cefpodoxime) - unnecessarily expensive and select for resistant flora 1
• Tetracyclines - high resistance rates 1
• Sulfonamides/TMP-SMX - do not eradicate GAS 1
• Fluoroquinolones - unnecessarily broad spectrum 1

Indications for Treating Streptococcal Pharyngitis

Only treat when GAS infection is confirmed by testing - do not treat empirically based on symptoms alone 3

When to Test:

Test patients with symptoms suggestive of GAS pharyngitis using rapid antigen detection test (RADT) and/or throat culture 3. Key clinical features that increase suspicion:

• Persistent fever (temperature >100.4°F/38°C) 4
• Anterior cervical adenitis (tender lymph nodes) 5, 4
• Tonsillopharyngeal exudates 5, 4
• Absence of cough (cough suggests viral etiology) 5, 6
• Age 5-15 years (though your patient is 32, GAS still causes 5-15% of adult pharyngitis) 5

Goals of Antibiotic Treatment:

1. Prevent acute rheumatic fever - the principal goal, though rare in adults 1, 7
2. Prevent suppurative complications (peritonsillar abscess) 3
3. Reduce symptom duration by 1-2 days (modest benefit - NNT of 6 at 3 days, 21 at 1 week) 3
4. Prevent bacterial transmission 3

Important note: Antibiotics do NOT prevent acute glomerulonephritis 3

Testing Strategy:

• Positive RADT = definitive, treat with antibiotics 3
• Negative RADT in adults = generally sufficient to rule out GAS (throat culture not routinely needed in adults, unlike children) 6

Common Pitfalls

1. Over-prescribing: More than 60% of adults with sore throat receive antibiotics, but only 10% actually have GAS 3, 6
2. Using azithromycin reflexively: Despite its convenience, recent high-quality evidence shows it has inferior efficacy and higher adverse events 2
3. Prescribing broad-spectrum agents: Stick to narrow-spectrum options to minimize resistance selection 1
4. Treating without confirmation: Always confirm GAS with testing before prescribing antibiotics 3