Metronidazole dosage question

What's the minimum effective dosage for a teenager in the treatment of
trichomoniasis? I've seen 2-g one time only, 1-g bid one day only,
250-mg tid 7 days, 500-mg bid 7 days. But considering the bad side
effects and carcinogenic nature of this drug, I am trying to see what
other people think about lower dosages. Would either a 1-g one time
only or say 750-mg bid one day only be enough?

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