A Comparison of Single-Dose Versus Multidose Metronidazole by Select Clinical Factors for the Treatment of Trichomonas vaginalis in Women

Background In a randomized controlled trial of 2 g (single-dose) metronidazole (MTZ) versus 500 mg twice daily for 7 days (multidose) for Trichomonas vaginalis treatment, multidose was superior. We examined if the effect was similar by select clinical factors to determine if treatment recommendations could be targeted. Methods The primary outcome was T. vaginalis repeat infection at test-of-cure (TOC) 4 weeks after completion of therapy. Analyses were stratified by T. vaginalis history, baseline genital symptoms, and concurrent diagnosis of bacterial vaginosis (BV) per Nugent score at baseline. Results Women who returned for TOC (n = 540) were included. At baseline, 52.9% had a self-reported history of T. vaginalis; 79.3%, genital symptoms; 5.8%, a gonorrhea diagnosis; and 47.5%, BV. During follow-up, 97.4% took all MTZ as instructed and 34.5% had interval condomless sex with a baseline partner. At TOC, 14.8% tested positive for T. vaginalis. In stratified analysis, women randomized to single-dose MTZ had a higher rate of TOC T. vaginalis positivity than those randomized to multidose if they were symptomatic at baseline (21.4% vs. 10.8%, P = 0.003) or had a reported history of T. vaginalis (24.1% vs. 12.6%, P = 0.01). Test-of-cure T. vaginalis positivity was higher for women receiving a single dose (18.9%) versus multidose (10.8%), irrespective of baseline BV status (P > 0.06). In multivariable analysis, only a history of T. vaginalis and single-dose MTZ were independently associated with a positive TOC for T. vaginalis. Conclusions Although multidose MTZ is recommended for all women with T. vaginalis, it is especially important for women with a T. vaginalis history and, given high posttreatment infection rates, a TOC should be performed.