Metabolic fate of pitavastatin, a new inhibitor of HMG-CoA reductase: similarities and difference in the metabolism of pitavastatin in monkeys and humans

Comparative Pharmacokinetics Between a Fixed-Dose Combination of Pitavastatin/Valsartan 4/160 mg and the Corresponding Individual Components Through a Partial Replicated Crossover Design in Healthy Male Subjects

Hypertension and hyperlipidemia are often comorbid, requiring combination therapies of antihypertensive drugs and antihyperlipidemia drugs. Taking 1 fixed-dose combination (FDC) may increase patient compliance rather than taking each of the drugs separately. This study aimed to evaluate the pharmacokinetic bioequivalence between an FDC of pitavastatin/valsartan 4/160 mg and the corresponding individual components. Considering that valsartan is a highly variable drug for maximum plasma concentration (C_max ), an open-label, randomized, partial replicated crossover study was conducted in 54 healthy subjects. The subjects received a single oral dose of the FDC of pitavastatin/valsartan 4/160 mg in 1 period or the corresponding individual components in the other 2 periods. The geometric mean ratios and their 90%CIs of the FDC to the corresponding individual components for C_max and area under the concentration-time curve from time 0 to the last measurable time point were 1.05 (90%CI, 0.96-1.15) and 0.10 (90%CI, 0.95-1.04) for pitavastatin and 1.15 (90%CI, 1.06-1.25) and 1.06 (0.99-1.14) for valsartan, respectively. The geometric mean ratios (90%CIs) for area under the concentration-time curve from time 0 to the last measurable time point and C_max of both drugs were included in the bioequivalence criteria. In conclusion, the FDC of pitavastatin/valsartan 4/160 mg showed pharmacokinetic equivalence with the corresponding individual components.

Pharmacokinetic herb-disease-drug interactions: Effect of ginkgo biloba extract on the pharmacokinetics of pitavastatin, a substrate of Oatp1b2, in rats with non-alcoholic fatty liver disease

ETHNOPHARMACOLOGICAL RELEVANCE

Ginkgo biloba L. is a traditional Chinese medicine for hyper lipaemia. Ginkgo flavonols and terpene lactones are responsible for the lipid-lowering effect in non-alcoholic fatty liver disease (NAFLD). However, the pharmacokinetics of ginkgo flavonols and terpene lactones in NAFLD was not clarified.

AIM OF THE STUDY

To investigate the effects of Ginkgo biloba L. leaves extracts (EGB) and NAFLD on hepatocyte organic anion transporting polypeptide (Oatp)1b2, and to assess the pharmacokinetics of EGB active ingredients in NAFLD rats.

MATERIALS AND METHODS

Male rats were fed with a high-fat diet to induce NAFLD models. The pharmacokinetic characteristics of EGB active ingredients were studied in NAFLD rats after two or four weeks of treatment with 3.6, 10.8, and 32.4 mg/kg EGB. The effects of NAFLD and EGB were investigated on the systemic exposure of pitavastatin, a probe substrate of Oatp1b2. The inhibitory effects of ginkgo flavonols and terpene lactones on OATP1B1-mediated uptake of ³H-ES were tested in hOATP1B1-HEK293 cells.

RESULTS

The plasma exposure of ginkgolides and flavonols in NAFLD rats increased in a dose-dependent manner following oral administration of EGB at 3.6-32.4 mg/kg. The half-lives of ginkgolides A, B, C, and bilobalide (2-3 h) were shorter than quercetin, kaempferol, and isorhamnetin (approximately 20 h). NAFLD reduced the plasma pitavastatin exposure by about 50 % due to the increased Oatp1b2 expression in rat liver. Increased EGB (from 3.6 to 32.4 mg/kg) substantially increased the C_max and AUC_0-t of pitavastatin by 1.8-3.2 and 1.3-3.0 folds, respectively. In hOATP1B1-HEK293 cells, kaempferol and isorhamnetin contributed to the inhibition of OATP1B1-mediated uptake of ³H-ES with IC₅₀ values of 3.28 ± 1.08 μM and 46.12 ± 5.25 μM, respectively.

CONCLUSIONS

NAFLD and EGB can alter the activity of hepatic uptake transporter Oatp1b2 individually or in combination. The pharmacokinetic herb-disease-drug interaction found in this research will help inform the clinical administration of EGB or Oatp1b2 substrates.

Comparative Hepatic and Intestinal Metabolism and Pharmacodynamics of Statins

This study aimed to comprehensively investigate the in vitro metabolism of statins. The metabolism of clinically relevant concentrations of atorvastatin, fluvastatin, pitavastatin, pravastatin, rosuvastatin, simvastatin, and their metabolites were investigated using human liver microsomes (HLMs), human intestine microsomes (HIMs), liver cytosol, and recombinant cytochrome P450 enzymes. We also determined the inhibitory effects of statin acids on their pharmacological target, 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase. In HLMs, statin lactones were metabolized to a much higher extent than their acid forms. Atorvastatin lactone and simvastatin (lactone) showed extensive metabolism [intrinsic clearance (CL_int) values of 3700 and 7400 µl/min per milligram], whereas the metabolism of the lactones of 2-hydroxyatorvastatin, 4-hydroxyatorvastatin, and pitavastatin was slower (CL_int 20-840 µl/min per milligram). The acids had CL_int values in the range <0.1-80 µl/min per milligram. In HIMs, only atorvastatin lactone and simvastatin (lactone) exhibited notable metabolism, with CL_int values corresponding to 20% of those observed in HLMs. CYP3A4/5 and CYP2C9 were the main statin-metabolizing enzymes. The majority of the acids inhibited HMG-CoA reductase, with 50% inhibitory concentrations of 4-20 nM. The present comparison of the metabolism and pharmacodynamics of the various statins using identical methods provides a strong basis for further application, e.g., comparative systems pharmacology modeling. SIGNIFICANCE STATEMENT: The present comparison of the in vitro metabolic and pharmacodynamic properties of atorvastatin, fluvastatin, pitavastatin, pravastatin, rosuvastatin, and simvastatin and their metabolites using unified methodology provides a strong basis for further application. Together with in vitro drug transporter and clinical data, the present findings are applicable for use in comparative systems pharmacology modeling to predict the pharmacokinetics and pharmacological effects of statins at different dosages.

Pharmacokinetic Properties of Single- and Multiple-Dose Pitavastatin Calcium Tablets in Healthy Chinese Volunteers

BACKGROUND

Pitavastatin is a newly developed 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor approved for the treatment of hyperlipidemia. Pharmacokinetic properties of pitavastatin have been studied previously.

OBJECTIVE

To investigate the pharmacokinetic properties of pitavastatin in healthy Chinese volunteers after single-dose and multiple-dose administration.

METHODS

An open-label, randomized, single-dose and multiple-dose study was conducted in healthy Chinese volunteers. The study included 4 stages, each separated with a 5-day washout period. A randomized, 3-way crossover design was carried out in Stages 1 to 3 for the single-dose study. Eligible subjects were randomized to receive a single 1 mg, 2 mg, or 4 mg pitavastatin calcium tablet. Blood samples were obtained predose and up to 36 hours following dosing. In Stage 4 the subjects received a 2-mg pitavastatin calcium tablet once daily for 6 days. At the last day of multiple dosing, blood samples were collected predose and up to 48 hours following dosing. Plasma pitavastatin was quantified by a validated liquid chromatography tandem mass spectrometry method. Tolerability was assessed by the adverse events, physical examination, 12-lead ECG, and laboratory tests.

RESULTS

Twelve volunteers (6 male and 6 female) were enrolled in the study and 11 of them completed all 4 study stages. Following a single dose of 1 mg, 2 mg, and 4 mg, the mean (SD) Tmax values were 0.63 (0.17) hours, 0.65 (0.17) hours, and 0.79 (0.36) hours, respectively; the corresponding Cmax values were 66.80 (16.32) ng/mL, 106.09 (31.59) ng/mL, and 232.91 (66.42) ng/mL, respectively. AUC0-36 values were 190.04 (38.97) ng/mL/h, 307.87 (57.94) ng/mL/h, and 785.10 (166.08) ng/mL/h, respectively, whereas t1/2 values were 10.99 (2.70) hours, 9.52 (2.58) hours, and 10.38 (4.28) hours, respectively. The AUC and Cmax showed dose proportionality after single dosing according to linear-regression analysis. In the multiple-dose study, a rapid absorption (Tmax of 0.68 [0.20] hours) and marked peak concentration of 90.99 (36.88) ng/mL were observed. AUC0-48 and AUCss were 306.28 (130.02) ng/mL/h and 256.16 (116.34) ng/mL/h, respectively. The elimination half-life after multiple dosing was significantly prolonged, which amounted to 13.31 (2.58) hours. Comparison of the pharmacokinetic parameters between the male and female groups revealed no significant differences.

CONCLUSIONS

In healthy Chinese volunteers, single dosing of 1 mg, 2 mg, and 4 mg pitavastatin resulted in linear plasma pharmacokinetic properties. Compared with single dosing, multiple dosing of pitavastatin showed different distribution and elimination characteristics. Sex did not appear to affect the pharmacokinetic properties of pitavastatin. Chictr.org identifier: ChiCTR-OO-13004294.

Evaluation of the pharmacokinetics and drug interactions of the two recently developed statins, rosuvastatin and pitavastatin

INTRODUCTION

Statins are the cornerstone of lipid-lowering therapy to reduce the risk of coronary heart disease. Rosuvastatin and pitavastatin are the two recently developed statins with less potential for drug interaction resulting in improved safety profiles.

AREAS COVERED

This review summarizes the pharmacokinetics and drug interactions of rosuvastatin and pitavastatin. The materials reviewed were identified by searching PubMed for publications using 'rosuvastatin', 'pitavastatin', 'statins', 'pharmacokinetics' and 'drug interaction' as the search terms.

EXPERT OPINION

Rosuvastatin and pitavastatin have favorable pharmacokinetic and safety profiles as their disposition does not depend on or is only marginally influenced by cytochrome P450 (CYP) enzymes, thus potentially reducing the risk of drug-drug interactions of these two statins with other drugs known to inhibit CYP enzymes. However, drug transporters play a significant role in the disposition of rosuvastatin and pitavastatin and drug interactions may occur through these. Genetic polymorphisms in drug transporters may also affect the pharmacokinetics, drug interactions and/or the lipid-lowering effect of these statins to a different extent.

Simple LC-MS/MS methods for simultaneous determination of pitavastatin and its lactone metabolite in human plasma and urine involving a procedure for inhibiting the conversion of pitavastatin lactone to pitavastatin in plasma and its application to a pharmacokinetic study

Sometimes, drugs and their metabolites in plasma may convert to each other. This phenomenon is called interconversion, which may result in the instability problem of the plasma samples. The instability problem caused by interconversion of the co-existing metabolites may often be ignored, since there is no drug metabolite in the quality control samples prepared for method validation. Pitavastatin lactone (Pi-LAC), a main metabolite of pitavastatin (Pi), is very unstable and easily converted to Pi in plasma. In this paper, simple and rapid LC-ESI-MS/MS methods were developed for the simultaneous determination of Pi and Pi-LAC in human plasma and urine. The sample stability was examined under different conditions. The interconversion of Pi and Pi-LAC was prevented by adding a pH 4.2 buffer solution to the freshly collected plasma samples. Detection was performed using an electrospray ionization (ESI) operating in positive ion multiple reaction monitoring mode by monitoring the ion transitions from m/z 422.2→290.3 (Pi), 404.2→290.3 (Pi-LAC) and m/z 611.3→423.2 (candesartan cilextetil, the internal standard), respectively. The calibration curve of Pi and Pi-LAC in both human plasma and urine showed good linearity over the concentration range of 0.1-200 ng/mL. The established methods were successfully applied to a pharmacokinetic study of pitavastatin calcium tablets in healthy Chinese volunteers after oral administration of 1, 2 and 4 mg single and multiple doses of pitavastatin calcium. The pharmacokinetic parameters of Pi and Pi-LAC in Chinese volunteers were given respectively. The urinary excretion profiles of Pi and Pi-LAC in Chinese volunteers were also presented. After receiving a single 4 mg oral dose of pitavastatin calcium, the average cumulative urinary excretion percentages of Pi and Pi-LAC in Chinese volunteers were (0.41 ± 0.16)% and (6.1 ± 5.0)%, respectively.

Intestinal absorption of HMG-CoA reductase inhibitor pitavastatin mediated by organic anion transporting polypeptide and P-glycoprotein/multidrug resistance 1

The purpose of this study was to investigate the involvement of organic anion transporting polypeptide (OATP/Oatp) and P-glycoprotein (P-gp)/multidrug resistance 1 (MDR1/Mdr1) in intestinal absorption of pitavastatin. Pitavastatin was found to be a substrate for human OATP1A2, OATP2B1, and MDR1 and rat Oatp1a5, Oatp2b1, and Mdr1a in experiments using transporter-expressing Xenopus oocytes and LLC-PK1 cell systems. Naringin inhibited Oatp1a5- and Mdr1a-mediated transport of pitavastatin with IC(50) values of 18.5 and 541 µM, respectively. The difference in the IC(50) values of naringin for Oatp1a5 and Mdr1a-mediated pitavastatin transport may account for the complex concentration-dependent effect of naringin on the intestinal absorption of pitavastatin. Rat intestinal permeability of pitavastatin measured by the in situ closed-loop perfusion method was indeed significantly reduced by 200 µM naringin, but was significantly increased by 1000 µM naringin. Furthermore, the permeability was significantly increased by elacridar, a potent inhibitor of Mdr1, while the permeability was significantly decreased in the presence of both elacridar and naringin, suggesting that Oatp1a5 and Mdr1a are both involved in intestinal absorption of pitavastatin. Our present results indicate that OATP/Oatp and MDR1/Mdr1 play roles in the intestinal absorption of pitavastatin as influx and efflux transporters, respectively.

Lack of effect of genetic polymorphisms of SLCO1B1 on the lipid-lowering response to pitavastatin in Chinese patients

AIM

To investigate the SLCO1B1 388A>G and 521T>C polymorphisms in hyperlipidemia patients and evaluate the effect of the two polymorphisms on the lipid-lowering efficacy of pitavastatin.

METHODS

The functional polymorphisms of SLCO1B1 (388A>G and 521T>C) were genotyped in 140 Chinese patients with essential hyperlipidemia using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and one-step tetra-primers ARMS-PCR. Eighty-five patients were enrolled in the clinical trial and given 2 mg of pitavastatin daily for 8 weeks. Total cholesterol (TC), triglyceride (TG), high-density lipoprotein (HDL), and low-density lipoprotein (LDL) serum levels were measured at baseline, after 4 weeks and after 8 weeks of treatment.

RESULTS

The allele frequencies of SLCO1B1 388A>G and 521T>C in essential hyperlipidemia patients were 71.1% and 11.1%, respectively. The 4- and 8-week treatment with pitavastatin significantly reduced TC, TG, and LDL levels, but there was no statistical difference among patients with wild type, SLCO1B1 388A>G or SLCO1B1 521T>C in the lipid-lowering efficacy of pitavastatin.

CONCLUSION

The present study found that the allele frequencies of SLCO1B1 388A>G and 521T>C in Chinese patients with essential hyperlipidemia are comparable to those in healthy Chinese population. SLCO1B1 388A>G and 521T>C do not affect the lipid-lowering efficacy of pitavastatin.

Metabolic properties of the acid and lactone forms of HMG-CoA reductase inhibitors

To gain a better understanding of the metabolic properties between the open acid and lactone form of HMG-CoA reductase inhibitors (statins), the paper focused primarily on characterizing the metabolic properties of statins. We compared the metabolism of the acid and lactone forms of several statins, including atrovastatin, simvastatin, cerivastatin fluvastatin, pitavastatin and rosuvastatin with respect to metabolic clearance, CYP enzymes involved and drug-drug interactions. A remarkable increase in metabolic clearance was noted for all lactones compared with all acids except for pitavastatin lactone. The metabolic clearances of the atrovastatin, simvastatin, cerivastatin, fluvastatin and rosuvastatin lactones were 73-, 70-, 30-, 7- and 64-fold higher, respectively, than those of the corresponding acids. CYP2Cs were critically involved in the metabolism of cerivastatin, fluvastatin and pitavastatin acids. In contrast, CYP2Cs were not involved in the metabolism of the corresponding lactones and CYP3A4 was mainly involved. Moreover, a substantial difference in the metabolic inhibition of statins was found between acids and lactones. Overall, the study demonstrates that CYP-mediated metabolism of lactones is also a common metabolic pathway for statins and that the CYP3A4-mediated metabolism of the lactone forms clearly will need to be taken into account in assessing mechanistic aspects of drug-drug interaction involving statins.

CYP2C76-mediated species difference in drug metabolism: A comparison of pitavastatin metabolism between monkeys and humans

The monkey is often used to predict metabolism of drugs in humans since it generally shows a metabolic pattern similar to humans. However, metabolic profiles different from humans are occasionally seen in monkeys for some drugs including pitavastatin. Recently, we have successfully identified a monkey-specific cytochrome P450 (CYP) 2C76, which possibly accounts for a species difference between monkeys and humans because of its sequence and functional uniqueness. The present study on the role of CYP2C76 and other monkey CYP2Cs in pitavastatin metabolism, as an example, has revealed that CYP2C76 is important for the metabolism of the lactone form, indicating a major role of CYP2C76 for the difference in the metabolism of pitavastatin and possibly other drugs between monkeys and humans. The current investigation on the involvement of CYP2C76 in the metabolism of other drugs is expected to reveal further the further importance of this monkey-specific drug-metabolizing enzyme.

The effect of SLCO1B1*15 on the disposition of pravastatin and pitavastatin is substrate dependent: the contribution of transporting activity changes by SLCO1B1*15

OBJECTIVE

This study was addressed to understand the underlying mechanism of the substrate-dependent effect of genetic variation in SLCO1B1, which encodes OATP1B1 (organic anion transporting polypeptide) transporter, on the disposition of two OATP1B1 substrates, pravastatin and pitavastatin, in relation to their transport activities.

METHODS

The uptake of pravastatin, pitavastatin, and fluvastatin was measured in oocytes overexpressing SLCO1B1*1a and SLCO1B1*15 to compare the alterations of in-vitro transporting activity. After 40-mg pravastatin or 4-mg pitavastatin was administered to 11 healthy volunteers with homozygous genotypes of SLCO1B1*1a/*1a and SLCO1B1*15/*15, the pharmacokinetic parameters of pravastatin and pitavastatin were compared among participants with SLCO1B1*1a/*1a and SLCO1B1*15/*15 genotypes.

RESULTS

The uptake of pravastatin and pitavastatin in SLCO1B1*15 overexpressing oocytes was decreased compared with that in SLCO1B1*15, but no change occurred with fluvastatin. The fold change of in-vitro intrinsic clearance (Clint) for pitavastatin in SLCO1B1*15 compared with SLCO1B1*1a was larger than that of pravastatin (P<0.0001). The clearance (Cl/F) of pitavastatin was decreased to a greater degree in participant with SLCO1B1*15/*15 compared with that of pravastatin in vivo (P<0.01), consistent with in-vitro study. As a result, Cmax and area under the plasma concentration-time curve of these nonmetabolized substrates were increased by SLCO1B1*15 variant. The greater decrease in the transport activity for pitavastatin in SLCO1B1*15 variant compared with SLCO1B1*1a was, however, associated with the greater effect on the pharmacokinetics of pitavastatin compared with pravastatin in relation to the SLCO1B1 genetic polymorphism.

CONCLUSION

This study suggests that substrate dependency in the consequences of the SLCO1B1*15 variant could modulate the effect of SLCO1B1 polymorphism on the disposition of pitavastatin and pravastatin.

SLCO1B1 (OATP1B1, an uptake transporter) and ABCG2 (BCRP, an efflux transporter) variant alleles and pharmacokinetics of pitavastatin in healthy volunteers

To investigate the contribution of genetic polymorphisms of SLCO1B1 and ABCG2 to the pharmacokinetics of a dual substrate, pitavastatin, 2 mg of pitavastatin was administered to 38 healthy volunteers and pharmacokinetic parameters were compared among the following groups: 421C/C(*)1b/(*)1b (group 1), 421C/C(*)1b/(*)15 (group 2), 421C/C(*)15/(*)15 and 421C/A(*)15/(*)15 (group 3), 421C/A(*)1b/(*)1b (group 4), 421A/A(*)1b/(*)1b (group 5), and 421C/A(*)1b/(*)15 (group 6). In SLCO1B1, pitavastatin area under plasma concentration-time curve from 0 to 24 h (AUC(0-24)) for groups 1, 2, and 3 was 81.1+/-18.1, 144+/-32, and 250+/-57 ng h/ml, respectively, with significant differences among all three groups. In contrast to SLCO1B1, AUC(0-24) in groups 1, 4, and 5 was 81.1+/-18.1, 96.7+/-35.4, and 78.2+/-8.2 ng h/ml, respectively. Although the SLCO1B1 polymorphism was found to have a significant effect on the pharmacokinetics of pitavastatin, a nonsynonymous ABCG2 variant, 421C>A, did not appear to be associated with the altered pharmacokinetics of pitavastatin.

Transporter-mediated influx and efflux mechanisms of pitavastatin, a new inhibitor of HMG-CoA reductase

The purpose of this study was to gain a better understanding of the transport mechanism of pitavastatin, a novel synthetic HMG-CoA reductase inhibitor. Experiments were performed using oocytes of Xenopus laevis expressing several solute carrier (SLC) transporters and recombinant membrane vesicles expressing several human ABC transporters. The acid form of pitavastatin was shown to be a substrate for human OATP1, OATP2, OATP8, OAT3 and NTCP, and for rat Oatp1 and Oatp4 with relatively low K(m) values. In contrast, these SLC transporters were not involved in the uptake of the lactone form. A significant stimulatory effect was exhibited by pitavastatin lactone, while the acid form did not exhibit ATPase hydrolysis of P-glycoprotein. In the case of breast cancer resistant protein (BCRP), the acid form of pitavastatin is a substrate, whereas the lactone form is not. Taking these results into consideration, several SLC and ABC transporters were identified as critical to the distribution and excretion of pitavastatin in the body. This study showed, for the first time, that acid and lactone forms of pitavastatin differ in substrate activity towards uptake and efflux transporters. These results will potentially contribute to the differences in the pharmacokinetic profiles of pitavastatin.

Effects of Acid and Lactone Forms of Eight HMG-CoA Reductase Inhibitors on CYP-Mediated Metabolism and MDR1-Mediated Transport

PURPOSE

With the growing clinical usage of 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors (statins), the number of reports concerning serious drug-drug interaction has been increasing. Because recent studies have shown that conversion between acid and lactone forms occurs in the body, drug-drug interaction should be considered on both acid and lactone forms. Thus, we investigated the inhibitory effects of acid and lactone forms of eight statins, including one recently withdrawn, cerivastatin, and two recently developed, pitavastatin and rosuvastatin, on cytochrome P450 (CYP) 2C8, CYP2C9, and CYP3A4/5 metabolic activities and multidrug resistance protein 1 (MDR1) transporting activity.

METHODS

The inhibitory effects of statins on CYP metabolic activities and MDR1 transporting activity were investigated using human liver microsomes and MDR1-overexpressing LLC-GA5-COL150 cells, respectively.

RESULTS

The acid forms had minimal inhibitory effects on all CYP activities tested, except for fluvastatin on CYP2C9-mediated tolbutamide 4-hydroxylation (IC50 = 1.7 microM) and simvastatin on CYP3A4/5-mediated paclitaxel 3-hydroxylation (12.0 microM). Lactone forms showed no or minimal inhibitory effects on CYP2C8, CYP2C9, and CYP2C19 activities, except for rosuvastatin on the CYP2C9 activity (20.5 microM), whereas they showed stronger inhibitory effects on the CYP3A4/5 activity with the rank order of atorvastatin (5.6 microM), cerivastatin (8.1 microM), fluvastatin (14.9 microM), simvastatin (15.2 microM), rosuvastatin (20.7 microM), and lovastatin (24.1 microM). Pitavastatin and pravastatin had little inhibitory effect, and a similar order was found also for testosterone 6beta-hydroxylation. MDR1-mediated transport of [3H]digoxin was inhibited only by lactone forms, and the rank order correlated with that of inhibitory effects on both CYP3A4/5 activities. Inhibitory effects on MDR1 activity, and on both CYP3A4/5 activities, could be explained by the lipophilicity; however, a significant correlation was found between the lipophilicity and inhibitory effects on CYP2C8-mediated paclitaxel 6alpha-hydroxylation.

CONCLUSIONS

We showed the difference between the acid and lactone forms in terms of drug interaction. The lipophilicity could be one of the important factors for inhibitory effects. In the case of statins, it is important to examine the effects of both forms to understand the events found in clinical settings, including the pleiotropic effects.

Pitavastatin

The growing number of trials that have highlighted the benefit of intensive lowering of total- and low density lipoprotein (LDL)-cholesterol levels especially with statins has created a need for more efficacious agents. Pitavastatin is a new synthetic 3-hydroxy-3-methyl glutaryl coenzyme A reductase inhibitor, which was developed, and has been available in Japan since July 2003. Metabolism of pitavastatin by the cytochrome P450 (CYP) system is minimal, principally through CYP 2C9, with little involvement of the CYP 3A4 isoenzyme, potentially reducing the risk of drug-drug interactions between pitavastatin and other drugs known to inhibit CYP enzymes. To date, human and animal studies have shown pitavastatin to be potentially as effective in lowering LDL-cholesterol levels as rosuvastatin; although, head-to-head studies are yet to be conducted.

Effect of Gemfibrozil on the Metabolism of Pitavastatin - Determining the Best Animal Model for Human CYP And UGT Activities

A series of studies was conducted to determine the best animal model for human CYP and UGT activities. The investigation focused primarily on the interactions occurring in the CYP- or UGT-mediated metabolism of pitavastatin, and involved in vitro and in vivo experiments. We found that the best animal models for human CYP-mediated hydroxylation and UGT-mediated lactonization of pitavastatin were rats and dogs, respectively. In addition, a large difference in the metabolic properties of pitavastatin was found between monkeys and humans. In the presence of gemfibrozil, the CYP- or UGT-mediated metabolism of pitavastatin was inhibited in vitro. However, gemfibrozil treatment had no inhibitory effect on the AUC of pitavastatin and its lactone form in rats and dogs. We conclude that the plasma level of pitavastatin would not be increased by co-administration of gemfibrozil in humans.