It is usually not given to children under 2 years of age.
Sulfasalazine metabolizes to sulfapyridine. Serum levels should be monitored every three months, and more frequently at the outset. Serum levels above 50 ?g/l are associated with side effects.
In rare cases, Sulfasalazine can cause severe depression in young males. It can also cause oligospermia and temporary infertility. Immune thrombocytopenia has been reported.
Sulfasalazine may cause stomach upset, nausea, vomiting, loss of appetite, headache, dizziness, or unusual tiredness. Skin and urine can become orange, with occasional allergic reactions.
Around 90% of a dose of sulfasalazine reaches the colon, where most of it is metabolized by bacteria into sulfapyridine and mesalazine (also known as 5-aminosalicylic acid or 5-ASA). Both metabolites are active; most of the sulfapyridine is absorbed and then further metabolized, but most mesalazine is not, and remains in the colon.
A mix of unchanged, hydroxylated, and glucuronidated sulfapyridine is eliminated in urine, as is acetylated mesalazine and unmetabolized sulfasalazine.
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