Pitavastatin has been studied for its effects on hepatic microsomal drug metabolism in rats, and the activities of several drug-metabolizing enzymes have been measured. No induction of the drug metabolizing enzymes (aniline hydroxylase, aminopyrine N-demethylase, 7-ethoxycoumarin O-deethylase and UDP-glucuronic acid transferase) was found in the pitavastatin group compared to the control after the multiple administrations of pitavastatin at the dosage of 1-10 mg/kg per day for 7 days. Based on several different in vitro approaches, it is concluded that CYP2C9 is the enzyme responsible for the metabolism of pitavastatin and no metabolite is present in renal and intestinal microsomes. The CYP2C9 polymorphism was not involved in the pitavastatin metabolism. No inhibitory effect in CYP-mediated metabolism was detected on the tolbutamide 4-hydroxylation (CYP2C9) and testosterone 6 beta-hydroxylation (CYP3A4) in the presence of pitavastatin. The results suggested that pitavastatin did not affect the drug-metabolizing systems.
Pitavastatin is marginally metabolized by CYP2C9 and to a lesser extent by CYP2C8. The major metabolite in human plasma is the lactone which is formed via an ester-type pitavastatin glucuronide conjugate by uridine 5'-diphosphate (UDP) glucuronosyltransferase (UGT1A3 and UGT2B7).
To elucidate any potential species differences, the in vitro metabolism of pitavastatin and its lactone was studied with hepatic and renal microsomes from rats, dogs, rabbits, monkeys and humans. With the addition of UDP-glucuronic acid to hepatic microsomes, pitavastatin lactone was identified as the main metabolite in several animals, including humans. Metabolic clearances of pitavastatin and its lactone in monkey hepatic microsome were much greater than in humans. M4, a metabolite of pitavastatin with a 3-dehydroxy structure, was converted to its lactone form in monkey hepatic microsomes in the presence of UDP-glucuronic acid as well as to pitavastatin. These results implied that lactonization is a common pathway for drugs such as 5-hydroxy pentanoic acid derivatives. The acid forms were metabolized to their lactone forms because of their structural characteristics. UDP-glucuronosyltransferase is the key enzyme responsible for the lactonization of pitavastatin, and overall metabolism is different compared with humans owing to the extensive oxidative metabolism of pitavastatin and its lactone in monkey.
Because pitavastatin is a relatively new agent, less information is available on its potential hepatotoxicity. In large clinical trials, pitavastatin therapy was associated with mild, asymptomatic and usually transient serum aminotransferase elevations in approximately 1% of patients, but levels above 3 times the upper limit of normal (ULN) were infrequent and no cases of clinically apparent hepatitis were reported from the preregistration clinical trials. Since marketing of pitavastatin, however, the sponsor has received reports of jaundice, hepatitis and hepatic failure including fatal cases. There has been only a single published report of liver injury due to pitavastatin, so that the clinical signature of hepatic injury associated with its use has not been defined. On the other hand, the other statins have all been implicated in cases of clinically apparent acute liver injury that typically arise after 1 to 6 months of therapy with either a cholestatic or hepatocellular pattern of serum enzyme elevations. Rash, fever and eosinophilia are uncommon, but some cases have been marked by autoimmune features including autoantibodies, chronic hepatitis on liver biopsy and a clinical response to corticosteroid therapy. This pattern has yet to be shown to apply to pitavastatin.
Pitavastatin is a substrate of organic anionic transport polypeptide (OATP) 1B1 (OATP2). Drugs that inhibit OATP1B1 (e.g., cyclosporine, erythromycin, rifampin) can increase bioavailability of pitavastatin.
Concomitant use of pitavastatin (2 mg once daily) and ezetimibe (10 mg for 7 days) decreased pitavastatin peak plasma concentration and AUC by 2 and 0.2%, respectively, and increased ezetimibe peak plasma concentration and AUC by 9 and 2%, respectively.
Erythromycin substantially increases pitavastatin exposure.1 Following concomitant use of pitavastatin (4 mg as a single dose on day 4) and erythromycin (500 mg 4 times daily for 6 days), pitavastatin peak plasma concentration and AUC were increased by 3.6- and 2.8-fold, respectively; such effects were considered clinically important. The interaction between pitavastatin and erythromycin probably resulted partly from erythromycin-induced inhibition of organic anionic transport polypeptide (OATP)1B1-mediated hepatic uptake of pitavastatin. If used concomitantly with erythromycin, dosage of pitavastatin should not exceed 1 mg once daily.
Concomitant use of pitavastatin (4 mg once daily on days 1-5 and 11-15) and extended-release diltiazem hydrochloride (240 mg on days 6-15) increased pitavastatin peak plasma concentration and AUC by 15 and 10%, respectively, and decreased diltiazem peak plasma concentration and AUC by 7 and 2%, respectively.
/MILK/ It is not known whether pitavastatin is excreted in human milk, however, it has been shown that a small amount of another drug in this class passes into human milk. Rat studies have shown that pitavastatin is excreted into breast milk.
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. 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. 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. 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.
A pharmacokinetics study was conducted in 12 Chinese volunteers following a single dose of 1 mg, 2 mg and 4 mg of pitavastatin calcium in an open-label, randomized, three-period crossover design. Plasma concentrations of pitavastatin acid and pitavastatin lactone were determined by a HPLC method. Single-nucleotide polymorphisms (SNPs) in ABCB1, ABCG2, SLCO1B1, CYP2C9 and CYP3A5 were determined by TaqMan (MGB) genotyping assay. An analysis was performed on the relationship between the aforementioned SNPs and dose-normalized (based on 1 mg) area under the plasma concentration-time curve extrapolated to infinity [AUC(0-infinity)] and peak plasma concentration (Cmax) values of the acid and lactone forms of pitavastatin. Pitavastatin exhibited linear pharmacokinetics and great inter-subject variability. Compared to CYP2C9*1/*1 carriers, CYP2C9*1/*3 carriers had higher AUC(0-infinity) and Cmax of pitavastatin acid and AUC(0-infinity) of pitavastatin lactone (P<0.05). With respect to ABCB1 G2677T/A, non-G carriers had higher Cmax and AUC(0-infinity) of pitavastatin acid, and Cmax of pitavastatin lactone compared to GT, GA or GG genotype carriers (P<0.05). Gene-dose effects of SLCO1B1 c.521T> C and g.11187G > A on pharmacokinetics of the acid and lactone forms were observed. Compared to non-SLCO1B1*17 carriers, SLCO1B1*17 carriers had higher Cmax and AUC(0-infinity) of the acid and lactone forms (P<0.05). Significant sex difference was observed for pharmacokinetics of the lactone. Female SLCO1B1 521TT subjects had higher Cmax and AUC(0-infinity) of pitavastatin lactone compared to male 521TT subjects, however, such gender difference disappeared in 521 TC and 521CC subjects. Pitavastatin pharmacokinetics was not significantly affected by ABCB1 C1236T, ABCB1C3435T, CYP3A5*3, ABCG2 c.34G > A, c.421C > A, SLCO1B1 c.388A>G, c.571T>C and c.597C>T. We conclude that CYP2C9*3, ABCB1 G2677T/A, SLCO1B1 c.521T>C, SLCO1B1 g.11187G > A, SLCO1B1*17 and gender contribute to inter-subject variability in pitavastatin pharmacokinetics. Personalized medicine should be necessary for hypercholesterolemic patients receiving pitavastatin.
Pitavastatin is more than 99% protein bound in human plasma, mainly to albumin and alpha 1-acid glycoprotein, and the mean volume of distribution is approximately 148 L. Association of pitavastatin and/or its metabolites with the blood cells is minimal.
