You should be able to drink alcohol after taking cephalosporin for 3-7 days at the earliest. Drinking alcohol while taking cephalexin can cause a disulfiram reaction, and it is only recommended to wait until the cephalexin is metabolized cleanly in about 3-7 days before drinking alcohol. Disulfiram-like reaction is the reaction of drug and alcohol together, which manifests as weakness, dizziness, drowsiness, general flushing, headache, nausea, vomiting, and even decrease in blood pressure, shock and other reactions, and in serious cases, respiratory depression, deficiency, convulsions and cardiac malfunction, etc., which can be life-threatening.