Should you add penicillin (Penicillin VK) to a patient with tonsillitis who is already taking doxycycline (Doxycycline) for perioral dermatitis?

Management of Tonsillitis in a Patient Already Taking Doxycycline

Recommendation

Penicillin VK should be added to the treatment regimen for a patient with tonsillitis who is already taking doxycycline for perioral dermatitis. 1

Rationale for Adding Penicillin

1. Pathogen Coverage Gap:

   • Doxycycline is effective for perioral dermatitis 2 but is not the first-line treatment for Group A Streptococcal (GAS) pharyngitis/tonsillitis
   • Penicillin or amoxicillin remains the treatment of choice for GAS tonsillitis due to:
     • Narrow spectrum of activity
     • Few adverse effects
     • Modest cost
     • No documented resistance among GAS 1

2. Standard of Care:

   • The Infectious Diseases Society of America (IDSA) strongly recommends penicillin or amoxicillin as first-line therapy for GAS pharyngitis/tonsillitis 1
   • Treatment duration should be 10 days to ensure eradication of the organism and prevent sequelae of streptococcal disease 3

Dosing Recommendations

• Penicillin VK (oral):

  • Adults: 250 mg four times daily or 500 mg twice daily for 10 days
  • Children: 250 mg two or three times daily for 10 days 1

• Continue doxycycline at current dose (typically 100 mg twice daily) for perioral dermatitis 2

Important Considerations

Drug Interactions

• No significant interactions between penicillin and doxycycline that would preclude concurrent use

Penicillin Allergy

• If patient has penicillin allergy, alternative options include:
  • First-generation cephalosporins (if no history of immediate hypersensitivity to penicillin)
  • Clindamycin (7 mg/kg three times daily, maximum 300 mg per dose)
  • Clarithromycin (7.5 mg/kg twice daily, maximum 250 mg per dose) 1

Treatment Failure Concerns

• Bacteriologic failure rates with penicillin have increased over time and may reach approximately 30% 4
• Causes of treatment failure include:
  • Poor compliance with 10-day regimen
  • Beta-lactamase-producing bacteria protecting GAS
  • Reexposure to infected family members 5

Special Situations

• For patients with recurrent tonsillitis who have failed penicillin therapy, consider:
  • Clindamycin or amoxicillin-clavulanate, which have shown superior effects compared to penicillin in patients with recurrent acute pharyngo-tonsillitis 6

Follow-up

• Assess clinical response within 48-72 hours
• Complete the full 10-day course of penicillin even if symptoms resolve quickly 3
• No routine post-treatment testing is needed unless symptoms persist 1

Pitfalls to Avoid

• Do not shorten the duration of penicillin therapy below 10 days, as short-course penicillin (5 days) has been shown to be less effective for GAS pharyngitis 1
• Do not rely solely on doxycycline for treating tonsillitis, as it is not considered first-line therapy for GAS infections
• Avoid assuming that the current doxycycline regimen will adequately treat the tonsillitis, as the coverage is suboptimal for GAS