I'm on metronidazole for a bacterial infection 500 mg. I took my last pill on Thursday morning. Can I drink tonight?

Not a great idea. If ur just getting over an infection, ur body has been working hard with the help of those antibiotics to get 'you' better. Drinking alcohol is not really a good idea. There is a known drug reaction with alcohol. That said, the 'half-life' of metronidazole is relatively short, so after a few days it is washed out of ur system. Still, I would be against 'partying' after what you've just been thru.