No significant effect of the SLCO1B1 polymorphism on the pharmacokinetics of ursodeoxycholic acid

Purpose To investigate possible effects of the SLCO1B1 polymorphism on the pharmacokinetics of ursodeoxycholic acid (UDCA) and its metabolites in healthy volunteers. Methods In a crossover study with two phases, 15 healthy volunteers with the SLCO1B1*1A/*1A genotype, seven with the *1B/*1B genotype, and five with the *15/*15 or *5/*15 genotype ingested placebo or a single 150-mg dose of UDCA. Plasma concentrations of bile acids and their biosynthesis marker were determined up to 24 h post-ingestion by liquid chromatography-tandem mass spectrometry. Results The SLCO1B1 genotype had no significant effect on the pharmacokinetics of UDCA. The geometric mean ratios (95% confidence interval) of UDCA area under the plasma concentration-time curve from 0 to 12 h (AUC(0-12)) in subjects with the SLCO1B1*1B/*1B genotype and in subjects with the SLCO1B1*15/*15 or *5/*15 genotype to the AUC(0-12) in subjects with the SLCO1B1*1A/*1A genotype were 1.07 (0.85, 1.35; P=0.459) and 0.93 (0.75, 1.15; P=0.563), respectively. In addition, following either placebo or UDCA administration, the SLCO1B1 polymorphism showed no association with the AUC(0-24) of the glycine and taurine conjugates of UDCA, with endogenous bile acids, or with the incremental AUC(0-24) of a bile acid synthesis marker. Compared with placebo, UDCA ingestion increased the AUC(0-24) of cholic acid, glycochenodeoxycholic acid, glycocholic acid, and glycodeoxycholic acid by 1.5-, 1.1-, 1.2-, and 1.2-fold (P<0.05), respectively. Conclusions Genetic polymorphism in SLCO1B1 does not affect pharmacokinetics of UDCA, suggesting that OATP1B1 is not rate-limiting to the hepatic uptake of therapeutic UDCA. Further studies are required to clarify the mechanisms by which UDCA increases the plasma concentrations of endogenous bile acids.