Just checked some sites on the drug which say...
http://www.drugs.com/metronidazole.html
Do not drink alcohol while taking metronidazole. Flushing, fast heartbeats, nausea, and vomiting may occur when alcohol is ingested during metronidazole therapy.
http://www.medic8.com/healthguide/articles/met ronidazole.html
Alcohol: IMPORTANT: AVOID ALCOHOL
http://www.nlm.nih.gov/medlineplus/druginfo/us pdi/202365.html
Drinking alcoholic beverages while taking this medicine may cause stomach pain, nausea, vomiting, headache, or flushing or redness of the face. Other alcohol-containing preparations (for example, elixirs, cough syrups, tonics) may also cause problems. These problems may last for at least a day after you stop taking metronidazole. Also, this medicine may cause alcoholic beverages to taste different. Therefore, you should not drink alcoholic beverages or take other alcohol-containing preparations while you are taking this medicine and for at least 3 days after stopping it.