The most common sulfamethoxazole side effects are mild stomach upsets, such as nausea and diarrhea. It can also cause increased sensitivity to the sun, so patients using this drug should take precautions when sun exposure is unavoidable. A hat, long sleeves, long pants, and sun block should all be used. There are also serious, rare reactions that may occur.
Sulfamethoxazole is usually combined with trimethoprim. They are both antibiotics in the sulfanomide family, which means their potential side effects are the same. This combination is used most often to treat bacterial urinary tract infections caused by E. coli. It can also be used for ear infections, and others as determined by a health care provider. Experts believe that both drugs have the potential to cause birth defects.
Nausea, diarrhea and anorexia are the most common sulfamethoxazole side effects. Also possible are vertigo, headache, and general abdominal pain. A fever or rash may also occur as minor side effects, but they could also signal a more serious condition, such as Stevens-Johnson Syndrome. Anaphylaxis, a serious and possibly life threatening allergic reaction, is possible with any drug, but particularly with antibiotics. Swelling of the tongue and wheezing signal a medical emergency. Patients who have ever had a reaction to a sulfanomide should not take sulfamethoxazole.
Stevens-Johnson Syndrome is probably the most severe of the sulfamethoxazole side effects. Symptoms of this disorder include fever, itching, skin lesions and sores in the mouth. Since the skin sheds from the body, patients with Stevens-Johnson Syndrome must be treated in a hospital, sometimes in a burn unit. There is a high risk of infection since there are large open wounds. In some cases there is permanent skin damage, blindness, or organ damage.
Other serious sulfamethoxazole side effects include hepatitis, bloody diarrhea, seizures, and an enlarged thyroid. Patients experiencing these side effects should seek immediate medical attention. Most of these side effects can be treated and do not cause lasting damage.
Certain sulfamethoxazole side effects are associated with long-term use of the drug. This drug may cause a decrease in blood platelets, which leads to excessive bruising or bleeding. Patients who are taking this drug should contact his or her doctor immediately if this side effect is noticed. This drug may also cause hemolytic anemia, which is caused by the premature destruction of red blood cells or megaloblastic anemia, which is caused by enlarged red blood cells. Some patients may need to have periodic blood tests to monitor their platelet levels.