Dissociation between vascular and metabolic effects of nicotinic acid in Gilbert's syndrome.

The relationship between the vasodilating and the hyperbilirubinaemic effect of low and high doses (50 and 300 mg i.v.) of nicotinic acid was studied in baseline conditions and after indomethacin pretreatment in healthy controls and patients with Gilbert's syndrome (a condition characterized by fluctuating, nonhaemolytic unconjugated hyperbilirubinaemia). The hyperbilirubinaemic effect of nicotinic acid was confirmed to be more pronounced in Gilbert's syndrome patients than in controls. The magnitude of hyperbilirubinaemia in the two groups was not dependent on the dose of nicotinic acid or indomethacin pretreatment. A dose-dependent vasodilation which was inhibited by indomethacin could be demonstrated in both controls and Gilbert's syndrome subjects. Vasodilating properties of nicotinic acid were therefore found to be dissociated from the effect on bilirubin.