Wait until the prescribed regiment of Bactrim is completed; Bactrim and alcohol should not be combined at all. The combination of antibiotics and alcohol exacerbates the side effects of the antibiotic, especially for antibiotics like Bactrim (trimethoprim-sulfamethoxazole).
Patients who drink alcohol while taking Bactrim may experience adverse effects, such as fast heartbeats, warmth or redness under the skin, tingly feeling, nausea and vomiting. They must check food and medicine labels for alcohol content to be safe. Although alcohol does not reduce the effectiveness of most antibiotics, it can reduce energy levels and delay recovery from illness as well, says Mayo Clinic.