Boric Acid for Candida glabrata Infections
For Candida glabrata vulvovaginitis that is unresponsive to oral azoles, topical intravaginal boric acid, administered in a gelatin capsule, 600 mg daily for 14 days is strongly recommended as the treatment of choice. 1
Understanding Candida glabrata Infections
Candida glabrata is a non-albicans Candida species that presents unique treatment challenges:
- Unlike C. albicans, C. glabrata frequently demonstrates resistance to azole antifungals
- It accounts for approximately 20% of urinary Candida isolates in adults 1
- In diabetic patients with vulvovaginal candidiasis, C. glabrata can be isolated in up to 61.3% of cases 2
Treatment Algorithm for C. glabrata Infections
First-Line Treatment for Vulvovaginal C. glabrata:
- Boric acid vaginal suppositories: 600 mg daily for 14 days 1
Alternative Options (if boric acid fails):
- Nystatin intravaginal suppositories: 100,000 units daily for 14 days 1
- Topical 17% flucytosine cream: alone or combined with 3% AmB cream daily for 14 days 1
- Flucytosine cream has shown 90% success in women whose condition failed to respond to both boric acid and azole therapy 3
For Systemic C. glabrata Infections:
- Echinocandins (caspofungin, micafungin, or anidulafungin) are preferred for candidemia
- Amphotericin B may be required for severe infections
Why Boric Acid Works for C. glabrata
Boric acid is effective against C. glabrata for several reasons:
- It has broad-spectrum activity against many Candida species
- Unlike fluconazole, boric acid effectively inhibits growth across many isolates and morphologies 4
- It can inhibit hyphal formation and reduce biofilm biomass and metabolic activity 4
- Population-level variation for both susceptibility and tolerance is narrower for boric acid than fluconazole 4
Important Clinical Considerations
Diagnosis
Before proceeding with antifungal therapy, confirm diagnosis with:
- Wet-mount preparation using saline and 10% potassium hydroxide to demonstrate yeast
- Vaginal pH measurement (normal pH 4.0-4.5)
- Vaginal cultures for Candida species identification 1
Duration of Treatment
- Standard course: 14 days of boric acid therapy (600 mg daily)
- No advantage has been observed in extending therapy beyond 14 days 3
Monitoring and Follow-up
- Clinical response should be assessed after completing the 14-day course
- Persistent symptoms may indicate treatment failure or mixed infection
- Long-term mycological cure rates at 3 months are approximately 63.1% with boric acid 5
Safety Considerations
- Local side effects are uncommon with boric acid therapy 3
- Boric acid should not be taken orally as it is toxic if ingested
- Patients should be instructed to use only as directed vaginally
Special Populations
Diabetic Patients
- Diabetic women with C. glabrata VVC show higher mycological cure with boric acid compared to fluconazole (63.6% vs 28.6%) 2
- However, relapse rates at 3 months are similar between boric acid and fluconazole groups (63.1% vs 71.4% remain cured) 5
Pitfalls and Caveats
Misdiagnosis: Symptoms of vulvovaginal candidiasis can be nonspecific and may be caused by other infectious or non-infectious etiologies. Always confirm diagnosis before treatment.
Inadequate treatment duration: Complete the full 14-day course of boric acid therapy even if symptoms improve earlier.
Mixed infections: C. glabrata may coexist with other pathogens, most commonly bacterial vaginosis. Treatment of both conditions may be necessary for symptom resolution 6.
Recurrence: Despite initial cure, recurrence rates are high. Consider maintenance therapy in patients with recurrent infections.
Improper administration: Ensure patients understand that boric acid suppositories are for vaginal use only and not for oral consumption.