Boric Acid for Refractory Vulvovaginal Candidiasis and Ocular Use
For refractory vulvovaginal candidiasis, particularly Candida glabrata infections, use intravaginal boric acid 600 mg in a gelatin capsule once daily for 14 days; for ocular application, instill 1–2 drops every 3–4 hours as directed. 1, 2
Intravaginal Boric Acid for Refractory Vulvovaginal Candidiasis
Primary Indication and Dosing
Boric acid 600 mg intravaginal gelatin capsule once daily for 14 days is the first-line treatment for C. glabrata vulvovaginitis unresponsive to oral azoles. 1, 3 This represents a strong recommendation from the Infectious Diseases Society of America, though based on low-quality evidence. 1
The regimen achieves mycological cure rates of 70–77% in patients with azole-resistant infections. 3, 4 This is substantially higher than the <50% response rate seen with fluconazole monotherapy against C. glabrata. 3
Complete the full 14-day course regardless of early symptom improvement to ensure mycological eradication and prevent recurrence. 3
When to Use Boric Acid
Reserve boric acid for documented azole-resistant C. glabrata or other non-albicans infections confirmed by vaginal culture; do not use empirically for recurrent C. albicans infections. 5, 3
C. glabrata accounts for 10–20% of recurrent vulvovaginal candidiasis cases and demonstrates intrinsic reduced susceptibility to standard-dose azoles. 3
Vaginal culture is essential because microscopy cannot reliably differentiate C. glabrata (which does not form pseudohyphae) from C. albicans. 3
Alternative Treatments for Azole-Resistant Infections
If boric acid is unavailable, contraindicated, or fails:
Nystatin intravaginal suppositories 100,000 units daily for 14 days (strong recommendation, low-quality evidence). 1, 3
Topical 17% flucytosine cream alone or combined with 3% amphotericin B cream daily for 14 days (weak recommendation, low-quality evidence). 1, 3
Extended topical azole therapy (terconazole 0.4% or 0.8% cream for 7–14 days) may be attempted, but cure rates are substantially lower than for C. albicans. 5, 3
Safety Profile and Adverse Effects
Boric acid is safe when used at the recommended 600 mg daily dose for 14 days. 6 Available human and animal data suggest no significant systemic toxicity at this dosing. 6
Common local adverse effects include vaginal burning sensation (<10% of cases), watery discharge during treatment, and mild vaginal erythema. 4
Extending the course beyond 14 days raises the risk of chemical vaginitis and vulvar irritation. 5 If symptoms persist after 14 days, discontinue boric acid and perform wet-mount microscopy to differentiate active infection from chemical irritation. 5
Absolute Contraindications
Boric acid is contraindicated during pregnancy due to insufficient safety data and theoretical teratogenic risk. 5, 6, 7 Current guidelines recommend avoiding boric acid in pregnancy until more data become available. 6
For pregnant patients with confirmed C. glabrata infection, use extended topical azole regimens (clotrimazole 1% cream, miconazole 2% cream, or terconazole 0.4% cream, 5 g intravaginally daily for 7–14 days). 5
Maintenance Therapy for Recurrent Infection
After achieving initial cure with boric acid, nystatin vaginal suppositories 100,000 units daily have been used successfully for long-term suppression in women with recurrent C. glabrata infections. 3
An expert consensus panel recommends beginning topical maintenance at 1–3 times weekly after an initial full treatment course, with twice-weekly dosing most commonly utilized. 7
Maintenance therapy with boric acid is effective during treatment, but relapses are common (54.5% at 6 months) after discontinuation. 8
Critical Pitfalls to Avoid
Do not use fluconazole monotherapy for confirmed C. glabrata infection—it is ineffective at standard doses. 3
Do not resume boric acid if chemical vaginitis develops; switch to an alternative antifungal class. 5
Do not treat asymptomatic colonization (present in 10–20% of women); only symptomatic infections require therapy. 5, 3
Do not routinely treat sexual partners—vulvovaginal candidiasis is not a sexually transmitted infection. 5, 3
Ocular Application of Boric Acid
Dosing for Ophthalmic Use
- Instill 1–2 drops in the affected eye(s) every 3–4 hours, or as directed by a physician. 2 This FDA-approved dosing applies to boric acid ophthalmic solutions used as an eye wash or for minor eye irritation.
Safety Precautions for Ocular Use
Boric acid ophthalmic solutions are intended for external use only as a mild antiseptic and buffering agent. 2
Discontinue use and consult a physician if eye pain, vision changes, continued redness, or irritation persists beyond 72 hours. 2
Do not use if the solution becomes cloudy or discolored, or if the container is damaged. 2