What is the standard treatment for an adult patient diagnosed with strep throat?

Standard Treatment for Strep Throat in Adults

Prescribe penicillin V 500 mg twice daily for 10 days or amoxicillin 500 mg twice daily for 10 days as first-line treatment for confirmed Group A streptococcal pharyngitis in adults. 1, 2

Confirming the Diagnosis Before Treatment

Before prescribing antibiotics, confirm the diagnosis using clinical criteria and testing:

• Apply the Centor criteria to assess likelihood of streptococcal infection: fever, tonsillar exudates, tender anterior cervical lymphadenopathy, and absence of cough 1
• Do not test or treat patients with 0-2 Centor criteria, as streptococcal infection is unlikely 2, 3
• Perform rapid antigen detection testing (RADT) for patients with 3-4 Centor criteria before prescribing antibiotics 1
• Do not perform backup throat cultures after negative RADT in adults, as the incidence of Group A streptococcus is low and rheumatic fever risk is exceptionally low 1
• Avoid testing patients with viral features such as cough, rhinorrhea, hoarseness, or oral ulcers 1, 4

First-Line Antibiotic Regimens

For non-penicillin allergic patients with confirmed streptococcal pharyngitis:

• Penicillin V 500 mg orally twice daily for 10 days (or 250 mg four times daily for 10 days) 1, 2, 5
• Amoxicillin 500 mg orally twice daily for 10 days is equally effective and often preferred due to better palatability 1, 2, 6
• Benzathine penicillin G 1.2 million units intramuscularly as a single dose for patients unlikely to complete oral therapy 1, 5, 4

The 10-day duration is critical and should not be shortened, as this maximizes pharyngeal eradication and prevents rheumatic fever 1, 5, 4

Treatment for Penicillin-Allergic Patients

For Non-Anaphylactic Penicillin Allergy:

• First-generation cephalosporins such as cephalexin 500 mg twice daily for 10 days or cefadroxil 1 gram once daily for 10 days 1, 2, 4

For Immediate/Anaphylactic Penicillin Allergy:

• Clindamycin 300 mg three times daily for 10 days (preferred due to low resistance rates) 1, 2, 4
• Azithromycin 500 mg once daily for 5 days (acceptable alternative, though resistance is increasing in some regions) 1, 2, 7, 8
• Clarithromycin 250 mg twice daily for 10 days (note: significant resistance exists in some U.S. regions) 1, 8

Critical Pitfalls to Avoid

• Never use trimethoprim-sulfamethoxazole (Bactrim) due to 50% resistance rates 2
• Never use tetracyclines or sulfonamides due to high resistance and frequent treatment failures 1, 2
• Do not use cephalosporins in patients with immediate/anaphylactic penicillin reactions due to 10% cross-reactivity risk 4
• Do not shorten the antibiotic course below 10 days except for azithromycin's 5-day regimen, as shorter courses increase treatment failure and rheumatic fever risk 1, 4, 9
• Avoid prescribing antibiotics empirically without testing, as only 10% of adults with sore throat have streptococcal infection 8, 10, 3

Adjunctive Symptomatic Treatment

• Acetaminophen or NSAIDs (ibuprofen) for moderate to severe symptoms or high fever 1, 2
• Throat lozenges may provide additional symptomatic relief 1
• Avoid aspirin in children due to Reye syndrome risk 1, 2
• Do not use corticosteroids as adjunctive therapy 1, 2

When Not to Prescribe Antibiotics

• Do not treat asymptomatic household contacts unless special circumstances exist 1, 5
• Do not perform routine post-treatment testing in asymptomatic patients after completing therapy 1
• Do not treat chronic pharyngeal carriers experiencing viral infections, as they are unlikely to spread infection and are at minimal risk for complications 1, 4

Expected Clinical Benefits

Antibiotics provide modest benefit in confirmed streptococcal pharyngitis:

• Symptom reduction of 1-2 days compared to no treatment 1
• Prevention of suppurative complications such as peritonsillar abscess 1, 11
• Prevention of acute rheumatic fever (though extremely rare in adults) 1
• Earlier return to normal activities and reduced transmission 11