"To a colitic it's freedom," announces Smith Klein and French about Asacol, its answer to sulphasalazine, as the drug for colitis with fewer side effects. This anti-inflammatory, which goes by the generic name of mesalazine, is the latest offering f

Sulphasalazine, a salicylate chemically related to aspirin, has two components: mesalazine and sulphapyridine. As the latter is supposedly responsible for the majority of serious side effects associated with sulphasalazine acute intolerance syndrome, characterized by cramping, acute abdominal pain and bloody diarrhea, as well as lowered sperm count and function, S K & F have chemically split the drug and retained the supposedly safer half.

Nevertheless, mesalazine lists as potential side effects many of those of its parent drug, including headaches and, for a drug supposed to treat gastrointestinal problems, a surprising number of gut problems: nausea, abdominal pain and, yes, diarrhea. If it doesn't make you feel better, it may, incidentally, exacerbate colitis in patients who have had similar problems with sulphasalazine.

Reports have also come through of lowered blood cell count, pancreatitis, and hepatitis. The main worry, however, is potential kidney problems, such as interstitial nephritis (inflammation), nephrotic syndrome (low blood protein and fluid in the tissues) and even kidney failure with oral treatment, which is "usually reversible on withdrawal," says SK & F. This has particular relevance for patients on "maintenance" therapy with an open-ended prescription.

Mesalazine should be avoided by patients with a known sensitivity to salicylates or severe kidney impairment, children under two, nursing mothers and, unless essential, pregnant women.