The application of microbore UPLC/oa-TOF-MS and 1H NMR spectroscopy to the metabonomic analysis of rat urine following the intravenous administration of pravastatin

The metabonomic effects of hepatotoxic doses of pravastatin on the urinary metabolic profiles of female rats have been investigated using ultra performance liquid chromatography (UPLC)-oa-TOF-MS and, independently, by (1)H NMR spectroscopy. UPLC was performed using a 1 mm microbore column packed with 1.7 microm particles. Examination of the data obtained from the individual animals, aided by statistical interpretation of the data, made it possible to identify potential markers for toxicological effects, with both NMR and UPLC-MS analysis highlighting distinct changes in the urinary metabolite profiles. These markers, which included elevated taurine and creatine, as well as bile acids, were consistent with hepatotoxicity in some animals, and this hypothesis was supported by histopathological and clinical chemistry findings. The analytical data from both techniques could be used to define a metabolic "trajectory" as toxicity developed and to provide an explanation for the lack of hepatotoxicity for one of the animals. The two analytical approaches (UPLC-MS and NMR) were found to be complementary whilst the use of a 1mm i.d. x 100 mm column reduced the amount of sample required for analysis to 2 microL, compared with 10 microL for a 2.1mm i.d. x 100 mm column. The 1mm i.d. column also provided increased signal-to-noise without loss of chromatographic efficiency.

Effects of organic anion transporting polypeptide 1B1 haplotype on pharmacokinetics of pravastatin, valsartan, and temocapril

OBJECTIVE

Recent reports have shown that genetic polymorphisms in organic anion transporting polypeptide (OATP) 1B1 have an effect on the pharmacokinetics of drugs. However, the impact of OATP1B1*1b alleles, the frequency of which is high in all ethnicities, on the pharmacokinetics of substrate drugs is not known after complete separation of subjects with OATP1B1*1a and *1b. Furthermore, the correlation between the clearances of OATP1B1 substrate drugs in individuals has not been characterized. We investigated the effect of genetic polymorphism of OATP1B1, particularly the *1b allele, on the pharmacokinetics of 3 anionic drugs, pravastatin, valsartan, and temocapril, in Japanese subjects.

METHODS

Twenty-three healthy Japanese volunteers were enrolled in a 3-period crossover study. In each period, after a single oral administration of pravastatin, valsartan, or temocapril, plasma and urine were collected for up to 24 hours.

RESULTS

The area under the plasma concentration-time curve (AUC) of pravastatin in *1b/*1b carriers (47.4 +/- 19.9 ng.h/mL) was 65% of that in *1a/*1a carriers (73.2 +/- 23.5 ng.h/mL) (P = .049). Carriers of *1b/*15 (38.2 +/- 15.9 ng.h/mL) exhibited a 45% lower AUC than *1a/*15 carriers (69.2 +/- 23.4 ng.h/mL) (P = .024). In the case of valsartan we observed a similar trend as with pravastatin, although the difference was not statistically significant (9.01 +/- 3.33 microg.h/mL for *1b/*1b carriers versus 12.3 +/- 4.6 microg.h/mL for *1a/*1a carriers [P = .171] and 6.31 +/- 3.64 microg.h/mL for *1b/*15 carriers versus 9.40 +/- 4.34 microg.h/mL for *1a/*15 carriers [P = .213]). The AUC of temocapril also showed a similar trend (12.4 +/- 4.1 ng.h/mL for *1b/*1b carriers versus 18.5 +/- 7.7 ng.h/mL for *1a/*1a carriers [P = .061] and 16.4 +/- 5.0 ng.h/mL for *1b/*15 carriers versus 19.0 +/- 4.1 ng.h/mL for *1a/*15 carriers [P = .425]), whereas that of temocaprilat (active form of temocapril) was not significantly affected by the haplotype of OATP1B1. Interestingly, the AUC of valsartan and temocapril in each subject was significantly correlated with that of pravastatin (R = 0.630 and 0.602, P < .01). The renal clearance remained unchanged for each haplotype for all drugs.

CONCLUSION

The major clearance mechanism of pravastatin, valsartan, and temocapril appears to be similar, and OATP1B1*1b is one of the determinant factors governing the interindividual variability in the pharmacokinetics of pravastatin and, possibly, valsartan and temocapril.

DISPOSITION OF ORAL AND INTRAVENOUS PRAVASTATIN IN MRP2-DEFICIENT TR–RATS

The aim of this study was to characterize the role of the efflux transporter Mrp2 (Abcc2) in the pharmacokinetics of orally and intravenously administered pravastatin in rats. Eight Mrp2-deficient TR- rats and eight wild-type rats were given an oral dose of 20 mg/kg pravastatin. Four TR- animals and four wild-type animals were studied after intravenous administration of pravastatin (5 mg/kg). The TR(-) rats showed a 6.1-fold higher mean area under the plasma concentration-time curve (AUC) of pravastatin (p < 0.001) after oral administration and a 4.7-fold higher AUC (p < 0.01) after intravenous administration of pravastatin as compared with the wild-type animals. The mean systemic (total) clearance of pravastatin was 4.6-fold higher (39.2 versus 8.50 l/h/kg, p < 0.001) and the mean V 4.3-fold higher (14.1 versus 3.29 l/kg, p < 0.01) in the wild-type rats. The mean renal clearance of pravastatin in the TR(-) rats was 16.5-fold increased as compared with the wild-type animals (0.695 versus 0.042 l/h/kg, p < 0.05). The increased systemic exposure to oral pravastatin in the TR- rats was associated with a greater inhibitory effect on 3-hydroxy-3-methylglutaryl CoA reductase, as shown by smaller lathosterol to cholesterol concentration ratios. These results suggest that the reduced biliary pravastatin excretion in the Mrp2-deficient TR- rats is partly compensated for by increased urinary excretion of pravastatin. Furthermore, intestinal Mrp2 does not appear to play a major role in the oral absorption of pravastatin in normal rats.

Quantification of pravastatin in human plasma and urine after solid phase extraction using high performance liquid chromatography with ultraviolet detection

A high performance liquid chromatography (HPLC) method for the estimation of pravastatin in human plasma and urine samples has been developed. The preparation of the samples was performed by automated solid phase extraction using clonazepam as internal standard. The compounds were separated by isocratic reversed-phase HPLC (C(18)) and detected at 239 nm. The method was linear up to concentrations of 200 ng/ml in plasma and 2000 ng/ml in urine. The intra-assay variability for pravastatin in plasma ranged from 0.9% to 3.5% and from 2.5% to 5.3% in urine. The inter-assay variability ranged from 9.1% to 10.2% in plasma and from 3.9% to 7.5% in urine. The validated limits of quantification were 1.9 ng/ml for plasma and 125 ng/ml for urine estimation. These method characteristics allowed the determination of the pharmacokinetic parameters of pravastatin after administration of therapeutic doses.

Evidence for inverse effects of OATP-C (SLC21A6) 5 and 1b haplotypes on pravastatin kinetics

OBJECTIVE

We compared the pharmacogenetic effects of OATP-C (organic anion transporting polypeptide C) *1a, *1b (A388G), and *5 (T521C) haplotypes on single-dose pharmacokinetics of pravastatin in white subjects.

METHODS

Thirty healthy white male subjects were grouped according to their OATP-C haplotype. Each group contained 10 individuals who were either homozygous or heterozygous carriers of the *1a, *1b, or *5 haplotype. After a single oral dose of 40 mg pravastatin, we analyzed kinetic parameters of pravastatin disposition.

RESULTS

Values for the area under the plasma concentration-time curve from time 0 to 6 hours [AUC(0-6)] in *1a/*1a, *1a/*1b or *1b/*1b, and *1a/*5 individuals were 114.5 +/- 68.6 microg. L(-1). h, 74.8 +/- 35.6 microg. L(-1). h, and 163.0 +/- 64.6 microg. L(-1). h, respectively, with highly significant differences across all 3 study groups (P =.006) and between subjects carrying the *1b and *5 haplotype (P =.002). Strikingly, values of AUC(0-6) from the OATP-C *1b group were more than 60% lower than those derived from carriers of the wild-type OATP-C *1a haplotype, although this difference failed to reach statistical significance. However, the amount of pravastatin excreted into the urine from time 0 to 12 hours [Ae(0-12)] was significantly diminished in the OATP-C *1b haplotype group (1729 +/- 907 microg) compared with *1a wild-type control subjects (2974 +/- 1590 microg) (P =.049).

CONCLUSION

There was a significant effect of tested OATP-C variant haplotypes on pravastatin disposition. Whereas *5 expression delayed the hepatocellular uptake of pravastatin, *1b expression seemed to accelerate OATP-C-dependent uptake of the drug.

Comparison of urinary excretion of pravastatin and temocapril in bile duct-ligated rats and Eisai hyperbilirubinemic rats (EHBR)

BACKGROUND/PURPOSE

In patients with complete bile duct obstruction, the only pathway for the elimination of cholephilic compounds is through the urine. Although changes in various transporters in the liver and kidney in cholestasis have been elucidated, little is known about how effectively the elimination of these compounds is compensated for by urinary excretion.

METHODS

In the present study, the urinary excretion of pravastatin and temocapril was studied in bile-duct-ligated rats (BDLR) for 3 days and in Eisai hyperbilirubinemic rats (EHBR). After urinary bladder cannulation, radiolabeled pravastatin and temocapril were injected intravenously. Urine samples were collected every 1 h for 4 h, and the radioactivity was counted.

RESULTS

Urinary excretion of pravastatin was markedly increased in BDLR (85.9% of the dose after 4 h) and moderately increased in EHBR (35.9% of the dose after 4 h) compared with that in control rats (5.5% of the dose after 4 h). Similar but less prominent differences were observed with temocapril after it was administered (50.7%, 38.2%, and 22.0% of the dose after 4 h in BDLR, EHBR, and the controls, respectively).

CONCLUSIONS

The absence of biliary excretion of anionic drugs was compensated for by urinary excretion in BDLR and EHBR, and the compensation was more efficient with pravastatin than with temocapril. In patients with complete bile duct obstruction, the only pathway for the elimination of cholephilic compounds is through the urine. Although changes in various transporters in the liver and kidney in cholestasis have been elucidated, little is known about how effectively the elimination of these compounds is compensated for by urinary excretion.

Gemfibrozil increases plasma pravastatin concentrations and reduces pravastatin renal clearance

BACKGROUND

Gemfibrozil increases the plasma concentrations of active acid forms of cerivastatin, lovastatin, and simvastatin. Pravastatin pharmacokinetics differs from those of these 3 statins, which are extensively metabolized. Our aim was to study the effects of gemfibrozil on the pharmacokinetics of pravastatin.

METHODS

A randomized, placebo-controlled, 2-phase crossover study was carried out. Ten healthy volunteers took gemfibrozil (1200 mg/d) or placebo for 3 days. On day 3, each subject ingested a single 40-mg dose of pravastatin. The concentrations of pravastatin and gemfibrozil in plasma and the cumulative excretion of pravastatin into urine were measured up to 24 hours.

RESULTS

During the gemfibrozil phase, the mean total area under the plasma concentration-time curve (AUC) of pravastatin from 0 hours to infinity was 202% (range, 40%-412%) of the corresponding value during the placebo phase (P <.05), but there was no difference in the half-life between the phases. The renal clearance of pravastatin was reduced from 25 L/h to 14 L/h by gemfibrozil (P <.0001), but the cumulative excretion of pravastatin into urine did not change significantly. The increase in the AUC of pravastatin from 0 to 24 hours correlated significantly with the decrease in the renal clearance of pravastatin (r = 0.72, P =.02). However, the change in renal clearance was only a minor contributor to the increase in pravastatin AUC.

CONCLUSIONS

Gemfibrozil increases plasma concentrations of pravastatin. This is partly but not solely the result of the reduced renal clearance of pravastatin. The increase in pravastatin AUC from 0 hours to infinity by gemfibrozil may represent an interference with a transport protein.

Biotransformation of pravastatin sodium in humans

Pravastatin sodium (PV) is a potent cholesterol-lowering agent that acts by inhibiting 3-hydroxy-3-methylglutaryl-coenzyme A reductase. Biotransformation profiles of PV in pooled human urine, plasma, and feces from healthy male volunteers given single 19.2-mg oral or 9.9-mg iv doses of [14C]PV were determined by HPLC. The predominant drug-related component in urine, plasma, and feces corresponded to intact PV; in the pooled urine samples, PV constituted 29 and 69% of the radioactivity after the po and iv doses, respectively. The delta 4.5-3 alpha-hydroxy isomer of PV constituted 10% (po) and 2% (iv), and 6-epi-PV constituted 3% (po) and 1% (iv) of the urinary radioactivity. Negligible amounts of the lactones of PV or its isomers were detected in urine, plasma, or feces. At least 15 other metabolites were also present; none of these accounted for more than 6% of the total urinary radioactivity. For metabolite isolation, an aliquot of pooled urine samples, obtained after administration of the radioactive dose, was added as a tracer to urine samples obtained from healthy subjects after administration of single nonradiolabeled 40-mg oral doses of PV. Urinary metabolites were concentrated on an XAD-2 column, extracted with ethyl acetate, and purified by extensive preparative HPLC. In addition to isolation and identification of unchanged drug and the two isomeric metabolites described above, eight other metabolites were isolated and structural assignments were made based on HPLC, UV spectra, mass spectral analysis, and proton NMR.(ABSTRACT TRUNCATED AT 250 WORDS)