My brother-in-law was an alcoholic and eventually lost his life to this disease. For him, it didn't matter if he was warned to decrease his use of alcohol while taking something like cephalexin because it didn't make any difference.
He wasn't very good about taking prescribed medications anyway, and sadly, the alcohol was more important to him than anything else. I remember once he complained about being dizzy after taking an antibiotic, so he quit taking it.
I am sure he never cut back on his alcohol while he was taking this medication, so the alcohol must have made the side effects even worse for him.