Treatment for Scarlet Fever
Oral Penicillin V (phenoxymethylpenicillin) 250-500 mg every 6-8 hours for 10 days is the first-line treatment for scarlet fever, as recommended by the Infectious Diseases Society of America and American Heart Association. 1
Primary Antibiotic Regimen
Penicillin V remains the drug of choice for treating scarlet fever caused by Streptococcus pyogenes. 1 The standard dosing is:
- Adults and children ≥40 kg: 250-500 mg orally every 6-8 hours (alternatively 500 mg twice daily or 250 mg three times daily) for 10 days 1
- Pediatric patients <40 kg: 25 mg/kg/day divided every 12 hours or 20 mg/kg/day divided every 8 hours for mild/moderate infections; 45 mg/kg/day divided every 12 hours or 40 mg/kg/day divided every 8 hours for severe infections 2
The full 10-day course must be completed to prevent acute rheumatic fever, even if symptoms resolve earlier. 1, 2 This is critical—at least 10 days of treatment is required for any S. pyogenes infection to prevent rheumatic fever complications. 2
Alternative Antibiotics for Penicillin Allergy
For patients with penicillin allergy (without immediate hypersensitivity), first-generation cephalosporins are recommended. 1 Cephalexin 500 mg orally four times daily for 7-10 days is an appropriate alternative. 3
For patients with true penicillin allergy or immediate hypersensitivity reactions, macrolides are recommended. 1 However, be aware that some strains of S. pyogenes may be resistant to macrolides. 1, 4 Azithromycin can be used but should not be relied upon as first-line therapy due to resistance concerns. 4
Never use sulfonamide antibiotics, as they are associated with increased disease severity and mortality in streptococcal infections. 1
Critical Timing Considerations
Antibiotics can be started up to 9 days after symptom onset and still prevent rheumatic fever, though early treatment reduces the infectivity period and morbidity. 1 The patient becomes non-contagious after 24 hours of antibiotic therapy. 1
Monitor for clinical improvement within 48-72 hours of starting antibiotics. 1 If symptoms persist beyond 3-5 days of antibiotic therapy, reassess the diagnosis and consider alternative pathogens or complications. 1
Adjunctive Management
Antipyretics may be used for symptomatic relief of fever but do not replace the need for antibiotics. 1 Never use aspirin in children under 16 years due to the risk of Reye's syndrome. 1
Take antibiotics at the start of a meal to minimize gastrointestinal intolerance. 2
Management of Close Contacts
Routine throat cultures or treatment for asymptomatic household contacts is generally not necessary. 1 However, in outbreak situations, throat cultures should be performed for all patients and only those with positive throat cultures should be treated. 1
Infection Control
Patients should be isolated for a minimum of 24 hours of effective antibiotic therapy. 1 Healthcare workers must use disposable gloves and aprons when in contact with the patient, with strict hand hygiene using soap and water or alcohol hand rub before and after patient contact. 1
Follow-up
Clinical follow-up is recommended to ensure resolution of symptoms. 1 Post-treatment throat cultures are not routinely recommended unless symptoms persist or recur. 1