Sulfasalazine is a prodrug, that is, it is not active in its ingested form. It is broken down by bacteria in the colon into two products: 5-aminosalicylic acid (5ASA), and sulfapyridine. There is some controversy as to which of these two products are responsible for the activity of azulfidine. Whereas it is known that 5ASA has therapeutic benefit, it is not clear whether sulfapyridine adds any further benefit. In the colon, the products created by the breakdown of sulfasalazine work as anti-inflammatory agents for treating inflammation of the colon. The beneficial effect of sulfasalazine is believed to be due to a local effect on the bowel, although there may also be a beneficial systemic immune-suppressant effect as well. Following oral administration, 33% of the sulfasalazine is absorbed, all of the sulfapyridine is absorbed, and about 33% of the 5ASA is absorbed.
Sulfasalazine is an anti-inflammatory medication that belongs to a class of drugs called sulfa drugs. The active ingredients in sulfasalazine consist of salicylate (the main ingredient in aspirin) combined with a sulfa antibiotic. Sulfasalazine is also known as a disease modifying antirheumatic drug (DMARD) because it not only decreases the pain and swelling of arthritis but also may prevent damage to joints and reduce the risk of long term disability. Sulfasalazine was first used to treat rheumatoid arthritis, once thought to develop after an infection and thus responsive to antibiotics. Today sulfasalazine is often given for mild symptoms or used in combination with other drugs for more severe symptoms or rheumatoid arthritis. It is also used to treat other conditions, including juvenile rheumatoid arthritis, ankylosing spondylitis, psoriatic arthritis and ulcerative colitis.
The exact way that sulfasalazine works is unknown, but it is believed to reduce the actions of substances in the body that cause inflammation, tissue damage, and diarrhea. Sulfasalazine is used to treat ulcerative colitis and to maintain remission. The delayed-release tablets, Azulfidine (EN-tabs), are also used to treat rheumatoid arthritis and juvenile rheumatoid arthritis. The drug sulfasalazine is a 5-ASA compound, and is the combination of two substances: sulfapyridine and an aspirin-like compound. It works to reduce the inflammation in the colon caused by ulcerative colitis and then as a maintenance therapy to maintain remission. Sulfasalazine may also be used to treat Crohn's disease in some cases.
Sulfasalazine is indicated for the treatment of mild to moderate ulcerative colitis, as adjunctive therapy in severe ulcerative colitis, and for the prolongation of the remission period between acute attacks of ulcerative colitis. Sulfasalazine is a prodrug comprised of mesalamine and sulfapyridine joined by a diazo bond. About one-third of a given dose of sulfasalazine is absorbed in the small intestine, while the remainder reaches the colon without being absorbed. Bacterial enzymes in the colon split the diazo bond, liberating the two components. About one-third of the mesalamine released in the colon is absorbed and excreted in the urine while the unabsorbed portion remains in the colon and is excreted in the feces. Most of the sulfapyridine released in the colon is absorbed, acetylated in the liver, and excreted in the urine.
The efficacy of sulfasalazine is dose-dependent, as are many adverse events of the drug. Doses greater than 4.0 g/d and serum sulfapyridine concentrations above 50 µg/ml are associated with a greater risk of toxicity. The sulfapyridine moiety is absorbed from the colon into the bloodstream and is considered responsible for much of the intolerance to sulfasalazine. The rate at which patients acetylate (deactivate) sulfapyridine affects the frequency of certain dose-related adverse events, with "slow acetylators" having more adverse events than rapid acetylators.