It takes around 7 days for metronidazole to cure and treat trichomoniasis.
Once you begin taking metronidazole or any other antibiotics for curing and treating trichomoniasis it should take around 7 days for the trichomoniasis to be cured after taking metronidazole.
If the trichomoniasis doesn't get better within 7 days or isn't cured completely or the condition trichomoniasis seems to be getting worse you should speak with your doctor and let them know.
The last time I had trichomoniasis and took the metronidazole the trichomoniasis cleared up and was cured after 7 days.
Continue taking the metronidazole until you use it all up even though it has cleared up because it keeps it from coming back.