Is it okay to drink alcoholic tonight if i took only 1 dose of bactrim (sulfamethoxazole and trimethoprim) this morning ?

OK to mix them: Like many people, you apparently assume that for some reason antibiotics and alcohol cannot be taken together. It isn't true: almost no antibiotics interact with alcohol. Of course heavy alcohol impairs the immune system's ability to fight infection. However, moderate alcohol intake is fine with Bactrim (sulfamethoxazole and trimethoprim) and almost all other antibiotics. You could even use wine or beer to swallow the medicine.