5-Aminosalicylic acid dimer

Olsalazine Dipentum Dimer of 5-aminosalicylic acid 1.5-3 g Colon... 

Chemical modification is also used to a limited extent to facilitate a dnig reaching its desired target (sec Chapter 3). An example is olsalazine. used in the treatment of ulcerative colitis. This drag is a dimer of (he pharmacologically active mesalamine (3-aminosalicylic acid). The latter is not effective orally because it is metabolized to inactive forms... 

There are oral formulations that deliver drug to the lower intestine. In mesalazine 5-amino-salicylic acid is formulated in a polymer-coated oral preparation. Olsalazine is a dimer of 5-aminosalicylate linked by an azo bond. Balsalazide is delivered to the colon where it is cleaved by bacterial azoreduction to release equimolar quantities of mesalazine and 4-aminobenzoyl-/i-alanine. The newer 5-ASA preparations were shown to be superior to placebo and tended towards therapeutic benefit over sulfasalazine. However, considering their relative costs, a clinical advantage to using the newer 5-ASA preparations in place of sulfasalazine appears unlikely. 

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