G6PD deficiency is a genetic disorder that affects the body’s ability to produce the enzyme glucose-6-phosphate dehydrogenase. This enzyme is essential for protecting red blood cells; when it is not present, the red blood cells can become damaged and break down. This can lead to a variety of symptoms, including anemia, jaundice, and fatigue. Glucose-6-phosphate dehydrogenase (G6PD) deficiency is a genetic disorder that mainly affects red blood cells, which carry oxygen from the lungs to tissues throughout the body. The G6PD gene is located on the X chromosome. In males, one altered gene copy in each cell is sufficient to cause the condition. In females, a mutation would have to occur in both copies of the gene to cause the disorder (except in the rare case of X-chromosome inactivation). Bactrim is a combination of two antibiotics: sulfamethoxazole and trimethoprim. It is used to treat certain bacterial infections, such as pneumonia, bronchitis, urinary tract, intestinal and ear infections. Common side effects of Bactrim include Nausea, vomiting, and diarrhea. Less common drug reactions include a severe skin rash called Stevens-Johnson syndrome and blood disorders such as agranulocytosis and hemolytic anemia. Anemia occurs when your blood doesn't have enough red blood cells. Hemolytic anemia develops when red blood cells are destroyed faster than bone marrow can replace them. Bactrim has been associated with hemolytic anemia in patients deficient in glucose-6-phosphate dehydrogenase (G-6-PD). Homozygotes and heterozygotes can be symptomatic, although the disease typically is more severe in persons who are homozygous for the deficiency. Because acute hemolysis is caused by exposure to an oxidative stressor like Bactrim, treatment is geared toward avoidance of these and other drugs like primaquine, pyridium, chloramphenicol, chloroquine, glibenclamide, methylene blue, nitrofurantoin, chloramphenicol, ciprofloxacin. Other genetic and clinical factors may also influence a patient's risk of drug-induced hemolysis. People with a G6PD deficiency should not take Bactrim, as it can be very dangerous. If you have a G6PD deficiency, it is important to tell your doctor before taking any medications. Your doctor may be able to prescribe an alternative antibiotic that is safe for you to take.