I had 2gms of metrobidazole flagyl oral. when will i see the effect of the med?

A few days: Metronidazole in a single 2g dose is used primarily for trichomonas, a vaginal infection. Symptoms like discharge and odor should start to improve in a couple of days and should be gone entirely in a week or so. However, this treatment is only 90% effective -- i.e. 10% of people aren't cured and need to take the drug for 5-7 days. Discuss with the doctor who prescribed it.