Disposition of quercetin in man after single oral and intravenous doses.
The pharmacokinetics of quercetin, a flavonoid, have been studied in 6 volunteers after single intravenous (100 mg) and oral (4 g) doses. The data after iv administration were analyzed according to a two compartment open model with half lives of 8.8 +/- 1.2 min for the alpha phase and 2.4 +/- 0.2 h for the beta phase (predominant half life), respectively. Protein binding was greater than 98%. The apparent volume of distribution was small at 0.34 +/- 0.03 1/kg. Of the intravenous dose 7.4 +/- 1.2% was excreted in urine as a conjugated metabolite, and 0.65 +/- 0.1% was excreted unchanged. After oral administration no measurable plasma concentrations could be detected, nor was any quercetin found in urine, either unchanged or in a metabolized form. These results exclude absorption of more than 1% of unchanged drug. Recovery in faeces after the oral dose was 53 +/- 5%, which suggests extensive degradation by microorganisms in the gut. The data obtained show that oral administration of flavonoids may be of questionable value.
D000284:Administration, Oral; D000328:Adult; D001798:Blood Proteins / Q000378:metabolism; D005260:Female; D005419:Flavonoids / Q000378:metabolism*; D006207:Half-Life; D006801:Humans; D007263:Infusions, Parenteral; D007700:Kinetics; D008297:Male; D008657:Metabolic Clearance Rate; D011485:Protein Binding; D011794:Quercetin / Q000008:administration & dosage / Q000378:metabolism*
D001798:Blood Proteins; D005419:Flavonoids; D011794:Quercetin