Boric Acid Suppositories for Vaginal Yeast Infections
Boric acid suppositories should be prescribed as second-line therapy at 600 mg intravaginally daily for 14 days, specifically for non-albicans Candida infections (particularly C. glabrata) that have failed conventional azole treatment, with approximately 70% clinical and mycologic eradication rates. 1
When to Prescribe Boric Acid
Primary Indications
- Non-albicans Candida infections unresponsive to azoles - This is the CDC-recommended indication, particularly for C. glabrata vulvovaginitis that has not responded to conventional azole therapy 1
- Recurrent vulvovaginal candidiasis (RVVC) with treatment failure - The CDC suggests boric acid for RVVC cases where conventional treatments have failed 1
- Azole-resistant Candida strains - Boric acid can be recommended for women with recurrent infections resistant to conventional therapies 2
When NOT to Use Boric Acid
- Do not use as first-line therapy for typical C. albicans infections, which respond well to conventional azole treatments 1
- Avoid during pregnancy - Boric acid should not be used in pregnant women 3
- Never use if patient has never had a vaginal yeast infection diagnosed by a doctor 4
Treatment Algorithm
Step 1: First-Line Treatment
- Start with topical azole agents (clotrimazole, miconazole, terconazole) for 7-14 days OR oral fluconazole 150 mg single dose 1
- For non-albicans species, attempt a longer duration (7-14 days) of non-fluconazole azole drug first 1
Step 2: When First-Line Fails or Recurs
- Prescribe boric acid 600 mg intravaginally once daily for 14 days 1
- Must be compounded by a pharmacist in gelatin capsules for specific patient use 1
Step 3: Maintenance for RVVC
- For women with confirmed RVVC, consider intermittent topical maintenance beginning at one to three times weekly after initial full course 3
- Twice weekly dosing is the most commonly utilized maintenance regimen 3
Diagnostic Confirmation Required
Before prescribing boric acid, ensure proper diagnosis:
- Confirm symptoms: pruritus, irritation, vaginal soreness, dysuria, dyspareunia 1
- Wet-mount preparation with saline and 10% KOH to demonstrate yeast or hyphae 1
- Check vaginal pH (should be 4.0-4.5 for Candida) 1
- Obtain vaginal cultures if wet mount is negative, to identify non-albicans species 1
Prescribing Details
Dosage and Administration
- 600 mg boric acid in gelatin capsule intravaginally once daily for 14 days 1
- For external vaginal use only 4
- Patient should be instructed that this requires pharmacy compounding 1
Expected Outcomes
- Clinical and mycologic eradication rates of approximately 70% 1
- Mycologic cure rates in studies have varied from 40% to 100% 5
- Particularly effective for C. glabrata compared to fluconazole (64.3% vs 12.5% cure rate) 6
Common Pitfalls and Adverse Effects
Side Effects to Counsel Patients About
- Mild vaginal burning sensation occurs in <10% of cases 5
- Watery discharge during treatment 5
- Vaginal erythema 5
- Mild increase in vaginal irritation or burning may occur 4
When to Stop and Reassess
- Stop use if symptoms persist or inflammation increases after 7 days 4
- Stop if abdominal pain increases or foul discharge develops 4
- Patient should seek medical care if symptoms persist after treatment or recur within 2 months 6
Critical Safety Warnings
- Keep out of reach of children - if swallowed, contact Poison Control immediately 4
- Do not use if allergic to any ingredients 4
- Avoid during pregnancy or breastfeeding - ask healthcare professional before use 4, 3
Mechanism Supporting Efficacy
Boric acid works through multiple antifungal mechanisms:
- Fungistatic to fungicidal depending on concentration and temperature 7
- Inhibits oxidative metabolism as a key antifungal mechanism 7
- Interferes with biofilm development and hyphal transformation 7
- Decreases cellular ergosterol at sub-MIC concentrations 7
- Particularly effective against azole-resistant strains, as C. glabrata shows >388-fold higher MIC for terconazole at vaginal pH 4 6