According to the Mayo Clinic, consuming alcohol while taking Bactrim is not recommended. Doing so may lead to serious side effects, such as a rapid heart rate, nausea and vomiting. While alcohol does not diminish the effectiveness of antibiotics, it may reduce how quickly one recovers.
Drugs.com explains that Bactrim is a combination of two antibiotics known as sulfamethoxazole and trimethoprim. It's useful for treating urinary tract infections, bronchitis and ear infections, among other ailments. Bactrim is contraindicated if the patient has severe liver or kidney disease, anemia or a history of low blood platelets. Pregnant women must avoid Bactrim as it may be harmful to an unborn baby.