Drinking and driving: It doesn’t take much alcohol to impair a person’s ability to drive. The chances of being killed in a single-vehicle crash are increased at a blood alcohol level that a 140-lb. woman would reach after having one drink on an empty stomach. Medication interactions: Alcohol can interact with a wide variety of medicines, both prescription and over-the-counter. Alcohol can reduce the effectiveness of some medications, and it can combine with other medications to cause or increase side effects. Alcohol can interact with medicines used to treat conditions as varied as heart and blood vessel disease, digestive problems,.