The tricyclic antidepressants can delay absorption of phenylbutazone and oxyphenbutazone from gut, but their antirheumatic effects are probably not affected.
Clinical evidence,mechanism, importance and management
The absorption of a single 400mg dose of phenylbutazone in 4 depressed women was considerably delayed (time to maximum level, 4 to 10 hrs compared with 2 hours), but total amount absorbed (measured by urinary excretion of oxyphenbutazone) remained unchanged when they were pretreated with desipramine 75mg daily for 7 days (See reference number 1). In another 5 depressed women half-life of oxyphenbutazone was found to be unaltered by 75mg of desipramine or nortriptyline daily (See reference number 2). Animal studies have confirmed that absorption of phenylbutazone and oxyphenbutazone are delayed by tricyclic antidepressants, probably because their antimuscarinic effects reduce motility of gut,(See reference number 3,4) but there seems to be no direct clinical evidence that antirheumatic effects of either drug are reduced by this interaction. No particular precautions appear to be needed.
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