Treatment of Strep Throat in a 93-Pound 12-Year-Old

For this 12-year-old patient weighing 93 pounds (42.3 kg), amoxicillin 750 mg orally twice daily for 10 days is the antibiotic of choice. 1

Calculating the Exact Dose

The patient weighs 93 pounds, which equals 42.3 kg 1
For streptococcal pharyngitis, the recommended pediatric dose is 25 mg/kg/day divided every 12 hours for mild-to-moderate infections 1
This calculates to 1,057 mg per day total, or approximately 528 mg per dose twice daily 1
Rounding to practical dosing: 750 mg twice daily (1,500 mg/day total) is appropriate and falls within the safe range, as severe infections can receive up to 45 mg/kg/day (1,903 mg/day for this patient) 1

Amoxicillin is preferred over penicillin V in children due to better taste acceptance and palatability, though both have equal efficacy 2
Penicillin V remains an acceptable alternative at 50-75 mg/kg/day divided into 3-4 doses (approximately 700-1,050 mg three times daily for this patient), but compliance is typically lower 3, 4
Both amoxicillin and penicillin have proven efficacy, narrow spectrum of activity, safety profiles, and low cost, with no documented resistance in Group A Streptococcus anywhere in the world 5

A full 10-day course is absolutely mandatory to achieve maximal pharyngeal eradication of Group A Streptococcus and prevent acute rheumatic fever 1, 3, 5
Treatment should continue for at least 10 days regardless of symptom resolution, as shortening the course even by a few days dramatically increases treatment failure rates and rheumatic fever risk 5, 2
Therapy can be safely postponed up to 9 days after symptom onset and still prevent acute rheumatic fever, but once started, the full 10 days must be completed 5

First-generation cephalosporins are the preferred alternative, with cephalexin 20 mg/kg per dose twice daily (approximately 420 mg twice daily for this patient) for 10 days 2, 5
Cross-reactivity risk is only 0.1% in patients with non-immediate penicillin reactions 5

Clindamycin 7 mg/kg per dose three times daily (approximately 100 mg three times daily for this patient) for 10 days is the preferred choice 5, 3
Azithromycin 12 mg/kg once daily (maximum 500 mg) for 5 days is acceptable but has 5-8% macrolide resistance rates in the United States 5, 3
Clarithromycin 7.5 mg/kg per dose twice daily (approximately 160 mg twice daily for this patient) for 10 days is also acceptable 5, 3

Do not prescribe courses shorter than 10 days (except azithromycin's 5-day regimen), as this leads to treatment failure and increased rheumatic fever risk 5, 2
Do not use cephalosporins in patients with immediate/anaphylactic penicillin reactions, as up to 10% may have cross-reactivity 2, 5
Do not use trimethoprim-sulfamethoxazole (Bactrim) for strep throat, as it has high resistance rates and is not effective against Group A Streptococcus 5
Routine post-treatment throat cultures are not recommended for asymptomatic patients who have completed therapy 5

Acetaminophen or ibuprofen should be considered for moderate to severe symptoms or high fever 5
Aspirin must be avoided in children due to Reye syndrome risk 5
Corticosteroids are not recommended as adjunctive therapy 5