I've only taken 3 metronidazole, last pill was at 5:30 yesturday , when is it ok to drink?

Metronidazole/ETOH: If you are taking Metronidazole for some infection, you should completely avoid alcohol use during the treatment course. Once committed to antibiotics, you need to finish the advised course. Once you are done with the treatment, you should be able to have alcohol in 1 or 2 days since half life of this medication is 8 hours.

See answer: Assuming you are taking the medication for an infection and not because you were rx'd it to stop drinking, than 48 hours after the meds should be fine, and should not cause any vomiting or GI upset. If you were rx'd it to help aide in stopping to drink alcohol, than do not drink alcohol at all. Best wishes.