Identification of Finasteride Metabolites in Human Bile and Urine by High-Performance Liquid Chromatography/Tandem Mass Spectrometry

Abstract

ABSTRACT:The objective of this study was to further investigate the metabolism of the 5␣-reductase inhibitor, finasteride, and to identify previously unknown phase I and phase II metabolites in vitro and in vivo in human bile and urine. Healthy volunteers were given 5 mg of finasteride, directly to the intestine, and bile and urine were collected for 3 and 24 h, respectively. A single-pass perfusion technique, Loc-I-Gut, was used for drug administration and bile collection from the proximal jejunum, distal to papilla of Vater. Incubations with human liver microsomes/S9 fractions and different cofactors were performed with finasteride and the previously known metabolites, -hydroxy finasteride (M1) and finasteride--oic acid (M3). Liquid chromatography coupled to triple quadrupole mass spectrometry (MS) with positive/negative electrospray ionization and ion trap with MS n measurements were used for structural investigations and identification of metabolites. Two hydroxy metabolites of finasteride, other than M1, and one intact hydroxy finasteride glucuronide were identified in vitro and in bile and urine. The glucuronide and at least one of the hydroxy metabolites were previously unidentified. M1 and M3 were glucuronidated in vitro by specific human UDP-glucuronosyltransferases, UGT1A4 and UGT1A3, respectively. M1 glucuronide was not identified in vivo, and M3 glucuronide, an acyl glucuronide, was present in low amounts in bile from a few individuals. In conclusion, previously undescribed metabolites were identified, in vitro and in human urine and bile. Bile collection using the Loc-I-Gut technique followed by sensitive mass spectrometry analysis led to the discovery of novel, both phase I and phase II, finasteride metabolites in human bile.

Metabolically Stable tert-Butyl Replacement

“…14 In this case, at least the 6-position can still be metabolically labile. 12,13 In conclusion, we have demonstrated an approach of removing all the fully sp 3 C−Hs from a tert-butyl group: replacing some H with F and increasing the s-character of the remaining C−Hs. This approach gave a trifluoromethylcyclopropyl group that consistently increased metabolic stability in vitro and in vivo compared to tert-butyl.…”

“…Finasteride ( 23) is known to be metabolized in humans predominantly on the tert-butyl (ω) but also at the 6-position (Figure 1). 12,13 Replacing the tert-butyl with Cp-CF 3 increased the t 1/2 in HLM from 63 min (23) to 114 min (24). This moderate increase is consistent with a caveat of the approach: replacing tert-butyl with Cp-CF 3 is not expected to substantially reduce metabolism at distal soft-spots.…”

In Vivo Investigation in Pigs of Intestinal Absorption, Hepatobiliary Disposition, and Metabolism of the 5α-Reductase Inhibitor Finasteride and the Effects of Coadministered Ketoconazole

“…Unfortunately, M1 was detected but was not present in quantifiable concentrations. Instead of M1, two other hydroxy metabolites were detected in urine and bile from the pigs (Lundahl et al, 2009b). The novel data from this pig study indicate that not only urinary excretion but also biliary excretion can be of importance for M3.…”

“…We were surprised to find that M1 was not present in quantifiable concentrations in the healthy volunteers administered finasteride before and after St. John's wort treatment, either in the normal or in the induced state (Lundahl et al, 2009a). Instead, two other hydroxy metabolites were isolated in human bile and urine (Lundahl et al, 2009b). Finasteride can be classified as a biopharmaceutical classification system class I compound (Amidon et al, 1995).…”

Evidence for the efficacy and safety of tadalafil and finasteride in combination for the treatment of lower urinary tract symptoms and erectile dysfunction in men with benign prostatic hyperplasia

“…In vitro studies have shown that finasteride is metabolized through an oxidative process by CYP450, specifically by the 3A4 and 2C19 isoenzymes [Chen et al 2009]. Finasteride is extensively metabolized in the liver to essentially inactive metabolites, including ω-hydroxyfinasteride and fineasteride-ω-oic acid [Lundahl et al 2009]. The majority of an oral dose is excreted through feces and bile (75%) compared with the urine (25%) and its half life is reported to be approximately 9 h [Wilde and Goa, 1999; Carlin et al 1992].…”