If a patient is on Doxycycline (Doxycycline) for allergies, should I prescribe Omnicef (Cefdinir) for sinusitis?

Management of Sinusitis in a Patient Taking Doxycycline for Allergies

Omnicef (cefdinir) can be safely prescribed for sinusitis in a patient already taking doxycycline for allergies, as there is no significant drug interaction between these medications and cefdinir provides appropriate coverage for common sinusitis pathogens.

Antibiotic Selection for Sinusitis

First-line Options

• For patients with mild sinusitis without recent antibiotic use, guidelines recommend:
  • Amoxicillin-clavulanate as first-line therapy 1
  • High-dose amoxicillin (90 mg/kg/day in children; 1.5-4g/day in adults) 1

Alternative Options (including for penicillin allergy)

• For patients with penicillin allergy, recommended alternatives include:
  • Cefdinir (Omnicef) 1
  • Cefpodoxime proxetil 1
  • Cefuroxime axetil 1

Rationale for Using Cefdinir (Omnicef)

Antimicrobial Coverage

• Cefdinir provides excellent coverage against common sinusitis pathogens:
  • Haemophilus influenzae (including β-lactamase producing strains)
  • Moraxella catarrhalis
  • Streptococcus pneumoniae (including many penicillin-resistant strains) 2, 3

Efficacy Evidence

• Clinical studies have demonstrated that cefdinir is as effective as amoxicillin-clavulanate for treating acute bacterial sinusitis, with approximately 90% cure rates 4
• Cefdinir has shown good distribution into sinus tissues 2

Dosing Convenience

• Cefdinir can be administered once or twice daily, improving compliance compared to medications requiring more frequent dosing 2, 3

Considerations When Using Doxycycline and Cefdinir Together

Drug Interactions

• No significant drug interactions exist between doxycycline and cefdinir
• Doxycycline is primarily used for allergies due to its anti-inflammatory properties, while cefdinir will address the bacterial infection

Side Effects

• Most common side effect of cefdinir is mild diarrhea (approximately 20% of patients) 4
• Cefdinir generally causes fewer adverse events requiring treatment discontinuation compared to some alternatives 4

Treatment Duration

• Standard duration for sinusitis treatment is 10-14 days 1
• Some experts recommend continuing therapy until the patient is symptom-free plus an additional 7 days 1

Important Caveats

• Ensure the diagnosis of bacterial sinusitis is accurate before prescribing antibiotics
• Bacterial sinusitis is typically diagnosed when symptoms persist >10 days or worsen after 5-7 days 1
• Avoid prescribing antibiotics for viral sinusitis, which is self-limiting 1, 5
• Consider adding intranasal corticosteroids and saline irrigation as adjunctive therapy 5

In conclusion, Omnicef (cefdinir) is an appropriate choice for treating sinusitis in a patient already taking doxycycline for allergies, providing good coverage against common sinusitis pathogens with a convenient dosing schedule and favorable side effect profile.