Why cant you drink alcohol with metronidazole?

A drug interaction exists between Metronidazole and alcohol, it is known as a "disulfiram-like reaction". If these two are ingested together or even within 48-72 hours of each other it can result in very severe vomiting.

Metronidazole gel, though used either topically (on the skin) or vaginally (inserted in the vagina), may result in a low amount/level of systemic absorption i.e. some of the drug may still get into your body system. If it does and you drink alcohol then you will have the very unpleasant reaction described above. It is for this reason that patients are advised to not drink alcohol whilst using Metronidazole gel.