Antibiotic Treatment for Concurrent Strep Pharyngitis and Infectious Mononucleosis
Penicillin V is the recommended first-line antibiotic treatment for patients diagnosed with both streptococcal pharyngitis and infectious mononucleosis, with a dosage of 250 mg three times daily or 500 mg twice daily for 10 days in adults. 1
Treatment Approach
First-line Treatment
- Penicillin V:
- Adults: 250 mg three times daily or 500 mg twice daily for 10 days
- Children: 600,000 U for <27 kg and 1,200,000 U for ≥27 kg for 10 days 1
Alternative Options for Penicillin-Allergic Patients
- Cephalexin: For non-anaphylactic penicillin allergy
- Macrolides (except azithromycin): For patients with true penicillin allergy
- Clindamycin: 300-450 mg orally three times daily for 10 days 1
Important Considerations
Avoid Ampicillin/Amoxicillin
- Critical warning: Patients with infectious mononucleosis who receive ampicillin or amoxicillin frequently develop a skin rash (up to 80-90% of cases) 2
- Therefore, despite amoxicillin being an alternative for strep pharyngitis alone, it should be avoided in patients with concurrent mono
Bacterial Superinfection in Mono
- Evidence shows that bacterial superinfection of the pharynx in infectious mononucleosis is relatively uncommon (less than 3% of cases) 2
- However, when Group A Streptococcus is confirmed by testing, treatment is necessary to prevent complications such as acute rheumatic fever 1, 3
Treatment Duration
- A full 10-day course of antibiotics is recommended to effectively eradicate streptococcal infection and prevent complications, particularly acute rheumatic fever 1, 3
- Shorter courses are not recommended even though symptoms may improve earlier
Diagnostic Considerations
- Confirm streptococcal pharyngitis with Rapid Antigen Detection Test (RADT) or throat culture before initiating antibiotics 1
- The presence of 3-4 Centor criteria suggests a higher likelihood of streptococcal infection 1
Supportive Care
- Adequate hydration and pain management are important adjuncts to antibiotic therapy
- Rest is particularly important for patients with infectious mononucleosis
- Patients should be advised to avoid contact sports until clinical recovery to prevent splenic rupture
Follow-up Recommendations
- Patients should be advised to complete the full antibiotic course even if symptoms improve
- Follow-up is recommended if symptoms persist beyond 3-5 days of antibiotic therapy
- Patients should be isolated for at least 24 hours after starting effective antibiotic therapy 1
Prevention of Complications
- The primary goal of antibiotic therapy for streptococcal pharyngitis is to prevent acute rheumatic fever and other complications 1, 3
- Despite the low incidence of bacterial superinfection in mono, treating confirmed strep infection remains important
The evidence strongly supports penicillin V as the first-line treatment for streptococcal pharyngitis, even in the presence of concurrent infectious mononucleosis, due to its proven efficacy, narrow spectrum, and five decades without development of resistance 1.