Most are accidental. Alcohol multiplies the effects of other depressants so that the effect of both is stronger and lasts longer than either alone. This effect can occur with common nonprescription medications like decongestants and allergy medications. Research is indicating that alcohol speeds up the absorption of carcinogenic tobacco by-products. As a consequence drinkers who also smoke face a greater risk of mouth, neck, and throat cancer.
Alcohol combined with aspirin can increase gastrointestinal bleeding.
Alcohol with Tylenol can increase liver damage. Alcohol reduces the theurapeutic effectiveness of antibiotics. Men have more muscle tissue which contains more fluid to dilute blood alcohol. Women are more susceptible to influences of alcohol just prior to and during menstruation. Although they consume less quantities of alcohol, women experience more serious physiological impairment earlier in their drinking careers than men.