<!-- Definition and medical uses -->
Sulfamethoxazole (SMZ or SMX) is an antibiotic. It is used for bacterial infections such as urinary tract infections, bronchitis, and prostatitis and is effective against both gram negative and positive bacteria such as Escherichia coli and Listeria monocytogenes.
<!-- Side effect and mechanism -->
Common side effects include nausea, vomiting, loss of appetite, and skin rashes. It is a sulfonamide and bacteriostatic. It resembles a component of folic acid. It prevents folic acid synthesis in the bacteria that must synthesize their own folic acid. Mammalian cells, and some bacteria, do not synthesize but require preformed folic acid (vitamin B9); they are therefore insensitive to sulfamethoxazole.
<!-- History, society and culture -->
It was introduced to the United States in 1961. It is now mostly used in combination with trimethoprim (abbreviated SMX-TMP). The SMX-TMP combination is on the WHO Model List of Essential medicines as a first-choice treatment for urinary tract infections. Other names include: sulfamethalazole and sulfisomezole.
Side effects
The most common side effects of sulfamethoxazole are gastrointestinal disturbances (nausea, vomiting, anorexia) and allergic skin reactions (such as rash and urticaria). There have been rare instances where severe adverse reactions have resulted in fatalities. These include Stevens–Johnson syndrome (SJS), toxic epidermal necrolysis, fulminant hepatic necrosis, agranulocytosis, aplastic anemia, and other blood dyscrasias. Type 1 reactions include immunoglobulin E (IgE)-mediated reactions such as urticaria, angioedema, and anaphylaxis. In contrast, non-type 1 hypersensitivities are believed to be caused by metabolites of sulfonamides. Therefore, the liver and kidney are the determining factors of these other hypersensitivity reactions; Of the allergic reactions, skin rashes, eosinophilia and drug fever were the most common, while serious reactions were less common.
Sulfamethoxazole is contraindicated in people with a known hypersensitivity to trimethoprim or sulfonamides. Hence, blockage of folate production inhibits the folate-dependent metabolic processes for bacterial growth. Since it inhibits bacterial growth, sulfamethoxazole is considered a bacteriostatic antibiotic.
Pharmacokinetics
Absorption
Sulfamethoxazole is well-absorbed when administered topically. It is rapidly absorbed when it is orally administered.
Distribution
Sulfamethoxazole distributes into most body tissues as well as into sputum, vaginal fluid, and middle ear fluid.