Improvement of the nicotinic acid test in the diagnosis of Gilbert's syndrome by pretreatment with indomethacin.

The hyperbilirubinemia induced by nicotinic acid (NA) is well correlated to 14C-bilirubin clearance, and is utilized to diagnose Gilbert's syndrome (GS). However, NA produces a number of vascular prostaglandin-mediated side effects. In an attempt to improve the NA test we evaluated the influence of pretreatment with Indomethacin, a PG-synthetase inhibitor, both on side effects and hyperbilirubinemia. NA (5.9 mumoles/kg of body weight i.v.) was administered on two separate occasions, before and one hour after i.m. injection of 100 mg Indomethacin in 11 GS males and 11 controls matched for sex and age (age range 18.34 years). The hyperbilirubinemic effect of NA was not modified by Indomethacin in any subject; the side effects were either significantly reduced or completely abolished. We suggest that patients undergoing the NA test for the diagnosis of GS be pretreated with Indomethacin.