What is the recommended antibiotic treatment for an adult patient with strep throat?

Antibiotic Treatment for Strep Throat in Adults

First-Line Treatment Recommendation

Penicillin V (500 mg twice daily for 10 days) or amoxicillin (500 mg twice daily for 10 days) are the drugs of choice for treating strep throat in adults. 1, 2, 3 These remain first-line because of proven efficacy, safety, narrow spectrum of activity, low cost, and complete absence of resistance in Group A Streptococcus after five decades of use 1, 2.

When to Prescribe Antibiotics

Do not prescribe antibiotics for patients with 0-2 Centor criteria (fever history, tonsillar exudates, absence of cough, tender anterior cervical lymphadenopathy), as these patients are unlikely to have streptococcal infection 1.

For patients with 3-4 Centor criteria, you have three evidence-based options 1:

• Test with rapid antigen detection and treat only if positive (preferred approach)
• Treat empirically without testing if 3-4 criteria present
• Use delayed prescribing (prescribe but instruct patient to fill only if symptoms worsen or persist beyond 48 hours) 1

The modest benefit of antibiotics (1-2 days symptom reduction) must be weighed against side effects, antibiotic resistance, and costs 1. Antibiotics do not need to be started immediately—therapy can be safely delayed up to 9 days after symptom onset and still prevent rheumatic fever 2.

Specific Dosing Regimens

For Non-Allergic Patients

• Penicillin V: 250 mg four times daily OR 500 mg twice daily for 10 days 2, 3
• Amoxicillin: 500 mg twice daily for 10 days (equally effective, often preferred due to twice-daily dosing) 2, 3, 4
• Benzathine penicillin G: 1,200,000 units intramuscular as single dose (use when oral compliance is uncertain) 2, 3

For Penicillin-Allergic Patients

The type of allergic reaction determines which alternative to use 2, 5:

Non-Immediate (Non-Anaphylactic) Penicillin Allergy

• First-generation cephalosporins are preferred with only 0.1% cross-reactivity risk 2, 5
• Cephalexin: 500 mg twice daily for 10 days 2, 3, 5
• Cefadroxil: 1 gram once daily for 10 days 2, 3

Immediate/Anaphylactic Penicillin Allergy

Avoid all beta-lactams (including cephalosporins) due to up to 10% cross-reactivity risk 2, 5

• Clindamycin: 300 mg three times daily for 10 days (preferred—only 1% resistance in US) 2, 3, 5
• Azithromycin: 500 mg once daily for 5 days (acceptable alternative but 5-8% resistance) 2, 3, 5, 6
• Clarithromycin: 250 mg twice daily for 10 days (similar resistance concerns as azithromycin) 2, 3

Critical Treatment Duration

A full 10-day course is mandatory for all antibiotics except azithromycin to achieve maximal pharyngeal eradication and prevent acute rheumatic fever 2, 3, 5. Azithromycin requires only 5 days due to its prolonged tissue half-life 2, 3, 6. Shortening courses below 10 days dramatically increases treatment failure rates and rheumatic fever risk 2, 3.

Common Pitfalls to Avoid

• Never use trimethoprim-sulfamethoxazole (Bactrim) for strep throat—50% resistance rate makes it ineffective 2, 3
• Never use tetracyclines or sulfonamides—high resistance and frequent treatment failures 2, 3
• Do not assume all penicillin-allergic patients need non-beta-lactam antibiotics—only those with immediate/anaphylactic reactions must avoid cephalosporins 2, 5
• Check local macrolide resistance patterns before prescribing azithromycin or clarithromycin—resistance varies geographically from 5-8% nationally but can be much higher regionally 2, 3, 5
• Azithromycin does not have proven data for preventing rheumatic fever, unlike penicillin 2, 6

Why Not Broader-Spectrum Antibiotics?

Although cephalosporins show statistically superior bacterial eradication rates compared to penicillin (OR 2.29-2.34 favoring cephalosporins), these differences are not clinically meaningful 1. The magnitude of benefit is small and does not justify routine use of broader-spectrum agents, which increase costs and selection pressure for resistant organisms 1, 2.

Adjunctive Symptomatic Treatment

• Acetaminophen or NSAIDs (ibuprofen) for moderate to severe symptoms 2, 3
• Avoid aspirin in children due to Reye syndrome risk 2, 3
• Corticosteroids are not recommended as adjunctive therapy 1, 3

When to Reevaluate

Patients with worsening symptoms after appropriate antibiotic initiation or symptoms lasting 5 days after starting treatment should be reevaluated 7. Routine post-treatment throat cultures are not recommended for asymptomatic patients who completed therapy 2, 5.