Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.6.3.44 (P-glycoprotein)
 13,344 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Grapefruit juice, a beverage consumed in large quantities by the general population, is an inhibitor of the intestinal cytochrome P-450 3A4 system, which is responsible for the first-pass metabolism of many medications. Through the inhibition of this enzyme system, grapefruit juice interacts with a variety of medications, leading to elevation of their serum concentrations. Most notable are its effects on cyclosporine, some 1,4-dihydropyridine calcium antagonists, and some 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors. In the case of some drugs, these increased drug concentrations have been associated with an increased frequency of dose-dependent adverse effects. The P-glycoprotein pump, located in the brush border of the intestinal wall, also transports many cytochrome P-450 3A4 substrates, and this transporter also may be affected by grapefruit juice. This review discusses the proposed mechanisms of action and the medications involved in drug-grapefruit juice interactions and addresses the clinical implications of these interactions.
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PMID:Drug-grapefruit juice interactions. 1099 29

The present study examined the interaction of four 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors (atorvastatin, lovastatin, and simvastatin in acid and lactone forms, and pravastatin in acid form only) with multidrug resistance gene 1 (MDR1, ABCB1) P-glycoprotein, multidrug resistance-associated protein 2 (MRP2, ABCC2), and organic anion-transporting polypeptide 1B1 (OATP1B1, SLCO21A6). P-glycoprotein substrate assays were performed using Madin-Darby canine kidney (MDCK) cells expressing MDR1, and the efflux ratios [the ratio of the ratio of basolateral-to-apical apparent permeability and apical-to-basolateral permeability between MDR1 and MDCK] were 1.87, 2.32/4.46, 2.17/3.17, and 0.93/2.00 for pravastatin, atorvastatin (lactone/acid), lovastatin (lactone/acid), and simvastatin (lactone/acid), respectively, indicating that these compounds are weak or moderate substrates of P-glycoprotein. In the inhibition assays (MDR1, MRP2, Mrp2, and OATP1B1), the IC50 values for efflux transporters (MDR1, MRP2, and Mrp2) were >100 microM for all statins in acid form except lovastatin acid (>33 microM), and the IC50 values were up to 10-fold lower for the corresponding lactone forms. In contrast, the IC50 values for the uptake transporter OATP1B1 were 3- to 7-fold lower for statins in the acid form compared with the corresponding lactone form. These data demonstrate that lactone and acid forms of statins exhibit differential substrate and inhibitor activities toward efflux and uptake transporters. The interconversion between the lactone and acid forms of most statins exists in the body and will potentially influence drug-transporter interactions, and may ultimately contribute to the differences in pharmacokinetic profiles observed between statins.
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PMID:Differential interaction of 3-hydroxy-3-methylglutaryl-coa reductase inhibitors with ABCB1, ABCC2, and OATP1B1. 1561 50

Understanding the mechanisms of drug interactions with 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors (statins) has become increasingly important because of the potential for serious adverse effects, most notably myopathy. Most of the evidence supports the role of cytochrome P450 (CYP) isoenzymes in many of these drug interactions. However, P-glycoprotein (P-gp), an efflux protein located in the gastrointestinal tract, placenta, kidneys, brain, and liver, may also play a role. Results of several studies with in vitro models have shown that lovastatin, simvastatin, and atorvastatin are inhibitors for P-gp and may be substrates for this transporter as well. Pravastatin and fluvastatin consistently demonstrate no significant inhibition of P-gp. Drug interaction studies involving statins and digoxin support a role for P-gp. Many additional drugs such as diltiazem, verapamil, itraconazole, ketoconazole, and cyclosporine, as well as dietary supplements such as St. John's wort and grapefruit juice, interact with statins and are modulators of both CYP3A4 and P-gp. However, the role of P-gp in these specific drug interactions remains unclear.
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PMID:Role of P-glycoprotein in statin drug interactions. 1706 5

In the present study, the ability of inhibitors of 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGCR), also known as statins, to regulate the gene expression and function of multidrug resistance protein 1 (MDR1/P-glycoprotein) and differences between their acid and lactone forms were examined in human intestinal epithelial LS180 cells. Some statins had the potential to induce the expression of mRNAs for MDR1 and/or CYP3A in either form. The change in the mRNA expression of MDR1 was accompanied by a change in the CsA-dependent intracellular accumulation of rhodamine 123. Simvastatin lactone, but not the acid form, exhibited a strong inductive effect on the mRNA expression of MDR1 and CYP3A in a dose-dependent manner. Sulforaphane significantly suppressed the expression of MDR1 and CYP3A mRNAs induced by atorvastatin lactone, lovastatin acid, and lovastatin lactone, comparable to the control level, and moderately inhibited that by cerivastatin acid, fluvastatin acid and simvastatin lactone. In the case of pitavastatin acid, sulforaphane had no significant effect on the expression of MDR1 mRNA.These results suggested that some statins could induce MDR1 and CYP3A gene expression and these inductive effects differed between the lactone and active hydroxy acid forms, and that PXR-mediated regulation was rarely associated with the mRNA inducibility by pitavastatin acid, unlike that by other statins.
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PMID:Effects of acid and lactone forms of 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors on the induction of MDR1 expression and function in LS180 cells. 1942 19

Pitavastatin has been designed as a synthetic 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor with a novel cyclopropyl moiety that results in several differences compared to other statins. These include effective inhibition of cholesterol synthesis and increased lipoprotein lipase expression at lower doses than other statins, and significant high-density lipoprotein-cholesterol and apolipoprotein A1-elevating activity that persists with time. The safety, tolerability and pharmacokinetics of pitavastatin and its major metabolite, pitavastatin lactone, have been investigated in a variety of patient groups with similar results, which suggests dosage adjustments are not required for gender, age or race. In healthy subjects, pitavastatin is well tolerated at the approved doses with no serious adverse events. The bioavailability of pitavastatin is, at 60%, higher than that of any other statin and the majority of the bioavailable fraction of an oral dose is excreted unchanged in the bile. The entero-hepatic circulation of unchanged drug contributes to the prolonged duration of action and allows once-daily, any-time dosing. Pitavastatin is only slightly metabolised by cytochrome P450 (CYP) 2C9 and not at all by CYP3A4. Neither pitavastatin nor its lactone form, have inhibitory effects on CYP, and CYP3A4 inhibitors have no effect on pitavastatin concentrations. Moreover, P-glycoprotein-mediated transport does not play a major role in the drug's disposition and pitavastatin does not inhibit P-glycoprotein activity. Pitavastatin is transported into the liver by several hepatic transporters but OATP1B1 inhibitors have relatively little effect on plasma concentrations compared with other statins. In general, interactions, except with multi-transporter inhibitors like ciclosporin, are not clinically significant. Consequently, pitavastatin has minimal drug-food and drug-drug interactions making it a treatment option in the large group of dyslipidaemic people that require multidrug therapy.
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PMID:Pitavastatin - pharmacological profile from early phase studies. 2119 52