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Letter to the Editor

Trichomonas vaginalis Treated With Boric Acid in a Metronidazole Allergic Female

Backus, Kandis Vechelle MS; Muzny, Christina A. MD; Beauchamps, Laura S. MD

Author Information
Sexually Transmitted Diseases: February 2017 - Volume 44 - Issue 2 - p 120
doi: 10.1097/OLQ.0000000000000559
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To the Editor:

Trichomonas vaginalis is considered to be the most common curable sexually transmitted infection.1 The mainstay of treatment is metronidazole and to a lesser extent tinidazole. Trichomoniasis is not a reportable disease. Due to the lack of surveillance data, the prevalence of trichomoniasis including metronidazole-allergic cases in the United States is unknown.1,2 To date, there are limited published data to support the use of intravaginal boric acid in patients with recurrent T. vaginalis or in patients who have hypersensitivity to nitroimidazole therapy.3,4 We provide additional support for the use of boric acid as a safe alternative for these patients; specifically, for patients that are not candidates for metronidazole desensitization.

A 67-year old white female presented to our sexually transmitted diseases clinic in April 2015 with a history of recurrent trichomonas infection. The patient was initially diagnosed with trichomoniasis via Pap smear and later confirmed via a nucleic acid amplification test (NAAT) by her primary care provider. She was then treated with oral metronidazole twice daily for 7 days. This treatment failed to eradicate the infection based on symptoms and a wet mount. At that time it was unclear if resistance had developed thus a second course of oral metronidazole twice daily for 7 days was prescribed. It was during her second round of treatment that she suffered from severe itching and lip swelling. This type I hypersensitivity reaction made her a poor candidate for desensitization. She discontinued the metronidazole due to this adverse reaction. At her next follow up with her primary care provider, her T. vaginalis NAAT test was again positive. She reported one lifetime partner (her husband), who admitted to having extramarital sexual relationship years before. He was subsequently treated as a contact to T. vaginalis infection. He was never tested for T. vaginalis. He was then diagnosed with prostate cancer and erectile dysfunction. The patient reported no subsequent vaginal intercourse and thus was not a reinfection case. The patient was then lost to care and would self-treat her symptoms of vaginal itching with an over-the-counter vaginal anti-itch cream. Several years after her initial diagnosis, the patient presented to our sexually transmitted diseases clinic due to a positive urine NAAT test for T. vaginalis at her gynecologist office. A repeat NAAT test confirmed T. vaginalis. Based on published literature, the patient was prescribed vaginal suppositories of boric acid 600 mg, US $2.19/suppository, to be inserted at bedtime daily for 45 days in conjunction with abstinence.4 At her follow-up appointment 2 months later, she presented with complaints of severe vaginal burning. At this visit, a T. vaginalis NAAT test was performed on a vaginal swab specimen, which was again positive. A second course of boric acid 600 mg vaginal suppositories, this time twice a day for 60 days was prescribed. At her next follow-up visit, the T. vaginalis NAAT was again performed on a vaginal swab specimen, and the results were negative. This case demonstrates that treatment with boric acid administered intravaginally twice daily for 60 days can successfully eradicate infection with T. vaginalis.

Kandis Vechelle Backus, MS
School of Pharmacy
University of Mississippi
Oxford, MS
Christina A. Muzny, MD
Division of Infectious Diseases
University of Alabama at Birmingham
Birmingham, AL
Laura S. Beauchamps, MD
Division of Infectious Diseases
University of Mississippi Medical Center
Jackson, MS


1."STD Facts—Trichomoniasis". N.p., 2016. Web. 18 July 2016.
2. Hawkins I, Carne C, Sonnex C, et al. Successful treatment of refractory trichomonas vaginalis infection using intravenous metronidazole. Int J STD AIDS 2015; 26:676–678 Web.
3. Brittingham A, Wilson WA. The antimicrobial effect of boric acid on Trichomonas vaginalis. Sex Transm Dis 2014; 41:718–722 Web. 19 Sept. 2016.
4. Muzny C, Barnes A, Mena L. Symptomatic Trichomonas vaginalis infection in the setting of severe nitroimidazole allergy: successful treatment with boric acid. Sex Health 2012; 9:389–391 Web. 18 July 2016.
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