Drug of Choice for Trichomonas Vaginalis
Metronidazole 500 mg orally twice daily for 7 days is the preferred treatment for trichomoniasis, with superior cure rates (approximately 90-95%) compared to the single 2-gram dose regimen. 1
Primary Treatment Regimen
The 7-day metronidazole regimen (500 mg twice daily) achieves significantly better cure rates than single-dose therapy, with treatment failure rates of only 11% versus 19% for the single 2-gram dose (p<0.0001). 2
While single-dose metronidazole 2 g has been widely used and FDA-approved, recent high-quality evidence demonstrates its inferiority to the 7-day regimen, particularly given that bacterial vaginosis does not modify treatment efficacy. 2
The CDC recommends metronidazole 500 mg orally twice daily for 7 days as the preferred regimen, with cure rates of approximately 90-95%. 1
Alternative Regimen
Metronidazole 2 g orally as a single dose remains an acceptable alternative when adherence to a 7-day regimen is unlikely, though it has higher failure rates. 1
Self-reported adherence is excellent with both regimens (96% for 7-day versus 99% for single-dose), and side effects are comparable between groups, with nausea being most common (23%). 2
Critical Management Principle: Treat Sexual Partners
All sex partners must be treated simultaneously to prevent reinfection, and patients should abstain from sexual intercourse until both they and their partners have completed treatment and are asymptomatic. 1
This is a common pitfall—failure to treat partners is a major cause of apparent treatment failure. 1
Treatment Failure Management
For first treatment failure: Re-treat with metronidazole 500 mg twice daily for 7 days. 1
For repeated treatment failure: Administer metronidazole 2 g once daily for 3-5 days. 1
If treatment continues to fail after excluding reinfection, consult an infectious disease specialist and consider susceptibility testing. 1
Special Population: Pregnancy
First trimester: Metronidazole is contraindicated during the first trimester due to theoretical teratogenicity concerns, though meta-analyses have not demonstrated consistent associations with congenital anomalies. 1, 3
Second and third trimesters: Pregnant women can be treated with metronidazole 2 g orally as a single dose after the first trimester. 1
Treatment is important during pregnancy as trichomoniasis is associated with premature rupture of membranes, preterm delivery, and low birthweight. 1
Special Population: HIV Infection
- Patients with HIV should receive the same treatment regimen as HIV-negative individuals—no dose adjustment is necessary. 1
Special Population: Metronidazole Allergy
Effective alternatives to metronidazole are not readily available. 1
Patients with immediate-type allergy may require desensitization. 1
Topical therapies (including intravaginal metronidazole gel or clotrimazole) have cure rates below 50% and are not recommended. 4, 5
Why Topical Therapy Fails
Metronidazole gel and other topically applied antimicrobials are considerably less efficacious (<50% cure rate) than oral preparations because they fail to achieve therapeutic levels in the urethra or perivaginal glands. 4
A study comparing clotrimazole vaginal tablets to oral metronidazole showed 88.9% treatment failure with clotrimazole versus only 20% failure with oral metronidazole (p<0.001). 5