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Letter to the Editor

Editor, – The New drug comment about balsalazide sodium (Aust Prescr 2005;28:104-6) described the use of this product by citing two 1998 studies which compared it to mesalazine in double-blind trials with ulcerative colitis patients.1,2

I wish to bring to your attention that the conclusions of these studies are not generalisable to the mesalazine products available in Australia, since the mesalazine product used in these studies (Asacol) is not marketed in this country. Asacol has a different coating from the mesalazine products marketed in Australia.

There are several mesalazine formulations available globally, which have different coatings and therefore different release mechanisms3,4,5 which may lead to different therapeutic efficacy. These different formulations are also supplied in different strengths. The only two oral formulations of mesalazine available in Australia are Salofalk and Mesasal which are delayed-release preparations of mesalazine coated with a resin that dissolves at a pH greater than six (the approximate pH of the ileum/colon). In contrast, Asacol consists of 400 mg of mesalazine destined for release in the terminal ileum or colon as its resin coating dissolves at a pH greater than seven.

Mesalazine products with different coatings are not therapeutically equivalent and are not interchangeable. The results of the Abacus Investigator Group studies therefore cannot be generalised to all mesalazine preparations, including the oral preparations available in Australia. Such generalisations would be misleading.

The comment also claims that 'mesalazine is absorbed, but is rapidly metabolised and excreted in the urine'. However, like balsalazide, very little mesalazine is systemically absorbed after being orally administered. The active drug is believed to act topically on the intestine and the main route of elimination is the faeces.6

Tim Bownas
Medical Affairs Associate
Orphan Australia Pty Ltd
Berwick, Vic.


Tim Bownas

Medical Affairs Associate, Orphan Australia Pty Ltd Berwick, Vic.