Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0023890 (cirrhosis)
 42,195 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Clopidogrel, a new platelet ADP receptor antagonist used for the prevention of vascular ischemic events, is converted to an active metabolite via the cytochrome P450 system. Patients with cirrhosis may not metabolize drugs normally and may, in addition, have a number of defects in the coagulation system. To assess the effect of cirrhosis on the pharmacokinetics and pharmacodynamics of clopidogrel, the authors performed an open-label, parallel-group study of 12 patients with Child-Pugh Class A or B cirrhosis and 12 matched controls. All 24 subjects received clopidogrel 75 mg PO QD for 10 days. Pharmacokinetics of clopidogrel and the major metabolite SR 26334 were analyzed on Days 1 and 10; pharmacodynamics were assessed by the inhibition of ADP-induced platelet aggregation and by bleeding time prolongation factor. Pharmacokinetic analysis of clopidogrel was limited due to low plasma concentrations arising from rapid hydrolysis to SR 26334. The Cmax at SS for clopidogrel was higher in cirrhotics than in normals. However, exposures to the metabolite SR 26334, as measured by AUC(tau), were comparable. At Day 10, there was not a statistically significant difference in mean inhibition of platelet aggregation (49.2% +/- 38.6% in cirrhotics vs. 66.7% +/- 7.5% in normals) or in bleeding time prolongation factor (1.64 +/- 0.49 in cirrhotics vs. 1.54 +/- 0.87 in normals) between groups. No significant adverse events, including bleeding events, were reported. In conclusion, there were no significant differences in the pharmacokinetics and pharmacodynamics of clopidogrel in this group of subjects with cirrhosis and matched normals. Therefore, no dosage adjustment of clopidogrel is required in patients with Child-Pugh Class A or B cirrhosis.
 ...
PMID:Cirrhosis does not affect the pharmacokinetics and pharmacodynamics of clopidogrel. 1076 Nov 67

Coumarin 7-hydroxylation is catalysed by a high-affinity CYP2A6 enzyme in human liver microsomes. CYP2A6 is the only enzyme catalysing this reaction and consequently the formation of 7-hydroxycoumarin can be used as 'an in vitro and in vivo probe' for CYP2A6. CYP2A6 is a major contributor to the oxidative metabolism of nicotine and cotinine, and it also contributes, to a larger or smaller extent, to the metabolism of a few pharmaceuticals (e.g. fadrozole), nitrosamines, other carcinogens (e.g. aflatoxin B1) and a number of coumarin-type alkaloids. CYP2A6 may be inducible by antiepileptic drugs and it is decreased in alcohol-induced severe liver cirrhosis. Several mutated or deleted CYP2A6 alleles have been characterized. Although CYP2A6 represent up to 15% of human microsomes P450 proteins, it is still one of the less well characterised cytochrome P450 enzymes.
 ...
PMID:CYP2A6: a human coumarin 7-hydroxylase. 1078 81

A 49-year old male patient with severe hemophilia A, coinfected with HIV and HCV, who underwent orthoptic liver transplantation because of hepatitis C cirrhosis is presented. We describe a strong interaction between nelfinavir and tacrolimus postoperatively, that caused a reduction of the dose of tacrolimus by a factor 70 compared with normal, to achieve therapeutic blood concentrations and to avoid toxic side effects. We suggest that nelfinavir inhibits the metabolism of tacrolimus because both compounds are well-known substrates for the cytochrome P450 isoenzyme CYP 3A4. The nelfinavir serum concentrations were not affected by the institution of tacrolimus. Although the interaction dramatically changed the tacrolimus dose-concentration relationship, the situation was manageable by frequent monitoring of blood concentrations of tacrolimus.
 ...
PMID:Interaction between nelfinavir and tacrolimus after orthoptic liver transplantation in a patient coinfected with HIV and hepatitis C virus (HCV). 1085 23

Liver diseases are associated with a decrease in hepatic drug elimination, but there is evidence that cirrhosis does not result in uniform changes of cytochrome P450 (CYP) isoenzymes. The objective of this study was to determine the content and activity of four CYP isoenzymes in the bile duct ligation and carbon tetrachloride (CCl4)-induced models of cirrhosis. The hepatic content of CYP1A, CYP2C, CYP2E1, and CYP3A was measured by Western blot analysis. CYP activity in vivo was evaluated with breath tests using substrates specific for different isoenzymes: caffeine (CYP1A2), aminopyrine (CYP2C11), nitrosodimethylamine (CYP2E1), and erythromycin (CYP3A). Bile duct ligation resulted in biliary cirrhosis; CYP1A, CYP2C and CYP3A content was decreased and the caffeine, aminopyrine, and erythromycin breath tests were reduced whereas CYP2E1 content and the nitrosodimethylamine breath test were unchanged compared with controls. CCl4 treatment resulted in cirrhosis of varying severity as assessed from the decrease in liver weight and serum albumin. In rats with mild cirrhosis, CYP content was comparable with controls except for a decrease in CYP2C. The activity of CYPs was also unchanged except for an increase in CYP2E1 activity. In rats with more severe cirrhosis, the content of all four CYP isoenzymes and the caffeine, aminopyrine, and erythromycin breath tests were reduced whereas the nitrosodimethylamine breath test was unchanged. In both models of cirrhosis, there was a significant correlation between the breath tests results and the severity of cirrhosis as assessed from serum albumin levels. These results indicate that content and the catalytic activity of individual CYP enzymes are differentially altered by cirrhosis in the rat and also suggest that drug probes could be useful to assess hepatic functional reserve.
 ...
PMID:Differential alteration of cytochrome P450 isoenzymes in two experimental models of cirrhosis. 1110 Sep 40

Deficiency of the fifth enzyme in haem synthesis, uroporphyrinogen decarboxylase (UPGD), may give rise to accumulation and excretion of poly-carboxylated porphyrins, as well as to clinical manifestations in the form of a phototoxic skin reaction and liver engagement leading to cirrhosis and hepatocellular cancer. The cutaneous reaction, presenting as skin fragility and blisters on areas exposed to sun--porphyria cutanea tarda (PCT)--develops only in individuals with a remaining hepatic UPGD activity less than 20% of normal. Experimental results and clinical observation give evidence that PCT is a multifactorial disease. In some individuals a 50%, decrease in UPGD activity is a consequence of inheritance of an allele with a mutation in the gene programming for the enzyme, but in these gene carriers, as well as in the other patients with overt PCT, the activity of the hepatic enzyme is reduced below the critical level by the action of specific inhibitors. In the generation of the enzyme inhibitors, iron plays a central role by promoting the formation of reactive oxygen species, a process where a specific class of cytochrome enzymes; cytochrome P450 1A (CYP4501A), participates. The varying individual susceptibility to development of the disease can be discussed in terms of differences in a spectrum of factors that affect the availability of the free form of this element in the liver, or its pathogenic action. In the article the roles of chronic viral infection, alcohol abuse and exposition to polyhalogenated cyclic hydrocarbons are considered in the light of effects on the availability of iron in the liver. Some genetic prerequisites for susceptibility to PCT-inducing agents are included in a tentative model for the disease, i.e. mutations in the UPGD gene and in the HFE gene affected in haemochromatosis, as well as genetically steered inducibilities of the genes programming for CYP4501A and the rate-limiting enzyme in haem synthesis, 5-aminolevulinate synthase. With the pathogenic model as a basis the different therapeutic strategies that can be applied are discussed, and suggestions for a handling programme for the patient presenting with PCT put forward.
 ...
PMID:Porphyrins, porphyrin metabolism, porphyrias. III. Diagnosis, care and monitoring in porphyria cutanea tarda--suggestions for a handling programme. 1120 50

Fluvastatin, the first fully synthetic HMG-CoA reductase inhibitor, has been shown to reduce cholesterol in patients with hyperlipidaemia, to prevent subsequent coronary events in patients with established coronary heart disease, and to alter endothelial function and plaque stability in animal models. Fluvastatin is relatively hydrophilic, compared with the semisynthetic HMG-CoA reductase inhibitors, and, therefore, it is extensively absorbed from the gastrointestinal tract. After absorption, it is nearly completely extracted and metabolised in the liver to 2 hydroxylated metabolites and an N-desisopropyl metabolite, which are excreted in the bile. Approximately 95% of a dose is recovered in the faeces, with 60% of a dose recovered as the 3 metabolites. The 6-hydroxy and N-desisopropyl fluvastatin metabolites are exclusively generated by cytochrome P450 (CYP) 2C9 and do not accumulate in the blood. CYP2C9, CYP3A4, CYP2C8 and CYP2D6 form the 5-hydroxy fluvastatin metabolite. Because of its hydrophilic nature and extensive plasma protein binding, fluvastatin has a small volume of distribution with minimal concentrations in extrahepatic tissues. The pharmacokinetics of fluvastatin are not influenced by renal function, due to its extensive metabolism and biliary excretion; limited data in patients with cirrhosis suggest a 30% reduction in oral clearance. Age and gender do not appear to affect the disposition of fluvastatin. CYP3A4 inhibitors (erythromycin, ketoconazole and itraconazole) have no effect on fluvastatin pharmacokinetics, in contrast to other HMG-CoA reductase inhibitors which are primarily metabolised by CYP3A and are subject to potential drug interactions with CYP3A inhibitors. Coadministration of fluvastatin with gastrointestinal agents such as cholestyramine, and gastric acid regulating agents (H2 receptor antagonists and proton pump inhibitors), significantly alters fluvastatin disposition by decreasing and increasing bioavailability, respectively. The nonspecific CYP inducer rifampicin (rifampin) significantly increases fluvastatin oral clearance. In addition to being a CYP2C9 substrate, fluvastatin demonstrates inhibitory effects on this isoenzyme in vitro and in vivo. In human liver microsomes, fluvastatin significantly inhibits the hydroxylation of 2 CYP2C9 substrates, tolbutamide and diclofenac. The oral clearances of the CYP2C9 substrates diclofenac, tolbutamide, glibenclamide (glyburide) and losartan are reduced by 15 to 25% when coadministered with fluvastatin. These alterations have not been shown to be clinically significant. There are inadequate data evaluating the potential interaction of fluvastatin with warfarin and phenytoin, 2 CYP2C9 substrates with a narrow therapeutic index, and caution is recommended when using fluvastatin with these agents. Fluvastatin does not appear to have a significant effect on other CYP isoenzymes or P-glycoprotein-mediated transport in vivo.
 ...
PMID:Clinical pharmacokinetics of fluvastatin. 1136 92

The aim of the present study was to investigate the time-course of changes in hepatic lipid peroxidation, cytochrome P450 and metallothionein concentrations, and superoxide dismutase and catalase activities in relation to the onset and development of cirrhosis in CCl4-treated rats. Further, the effects of oral zinc administration on these parameters were assessed. Cirrhosis was induced in 120 rats by intraperitoneal injections of CCl4 twice weekly over 9 weeks. Controls were 120 additional animals. Both groups were further subdivided to receive either a standard diet or one supplemented with zinc. Subsets of 10 animals each were euthanized at weeks 1, 2, 3, 5, 7 and 9 from the start of the study. Results indicated that zinc administration delayed the cirrhotic process and the increase in lipid peroxidation. These changes, consistently maintained during the first 5 weeks of the study, were associated with a significant decrease in the hepatic concentration of cytochrome P450 and an increase in the hepatic concentration of metallothioneins. Zinc supplementation did not produce any significant change in superoxide dismutase and catalase activities. These results suggest that cytochrome P450 and metallothioneins may play an important role in the hepato-protective effects of zinc against lipid peroxidation in experimental cirrhosis.
 ...
PMID:The antioxidant and hepatoprotective effects of zinc are related to hepatic cytochrome P450 depression and metallothionein induction in rats with experimental cirrhosis. 1158 58

Transjugular intrahepatic portosystemic shunt (TIPS) is performed to treat some complications of cirrhosis. This study investigated the effects of cirrhosis and TIPS on intestinal and hepatic cytochrome P450 3A (CYP3A) activity. Nine volunteers were cirrhotic patients with TIPS, 9 were cirrhotic controls (matched for sex, age, etiology, and Child-Pugh class), and 9 were sex- and age-matched healthy volunteers. Simultaneous doses of midazolam were given intravenously (0.05 mg/kg) and orally (3 mg of [15N3]midazolam). Peripheral and portal venous blood samples were assayed for midazolam and [15N3]midazolam. The systemic clearance of midazolam was significantly greater (P <.05) in healthy volunteers (0.42 +/- 0.10 L x h(-1) x kg(-1)) compared with cirrhotic controls (0.20 +/- 0.05) and with cirrhotic patients with TIPS (0.21 +/- 0.09). Hepatic availability followed the same trend. The bioavailability of midazolam was significantly higher (P <.05) in cirrhotic patients with TIPS (0.76 +/- 0.20) compared with cirrhotic controls (0.27 +/- 0.14) and with healthy volunteers (0.30 +/- 0.10). The intestinal availability was significantly greater (P <.05) in cirrhotic patients with TIPS (0.83 +/- 0.17) compared with cirrhotic controls (0.32 +/- 0.16) and with healthy volunteers (0.42+/-0.15). As expected, hepatic CYP3A activity was reduced in cirrhosis. However, in cirrhotic patients with TIPS, there was a marked loss in first-pass metabolism of midazolam as a result of diminished intestinal CYP3A activity.
 ...
PMID:Hepatic and intestinal cytochrome P450 3A activity in cirrhosis: effects of transjugular intrahepatic portosystemic shunts. 1202 46

Herbal hepatotoxicity is increasingly recognized as herbal medicines become more popular in industrialized societies. Some herbal products may potentially benefit people with liver disease; however, these benefits remain generally unproved in humans, and a greater awareness of potential adverse effects is required. Herbal use is often not disclosed, and this may result in a diagnostic delay and perpetuation or exacerbation of liver injury. Female gender may predispose to hepatotoxicity, and concomitant agents that induce cytochrome P450 enzymes may also increase individual susceptibility. The range of liver injury includes minor transaminase elevations, acute and chronic hepatitis, steatosis, cholestasis, zonal or diffuse hepatic necrosis, hepatic fibrosis and cirrhosis, veno-occlusive disease, and acute liver failure requiring transplantation. In addition to the potential for hepatotoxicity, drug-drug interactions between herbal medicines and conventional agents may affect the efficacy and safety of concurrent medical therapy. This review focuses on emerging hepatotoxins and patterns of liver injury, potential risk factors for herbal hepatotoxicity, and herb-drug interactions. Appropriate reporting and regulatory systems to monitor herbal toxicity are required, in conjunction with ongoing scientific evaluation of the potential benefits of phytotherapy.
 ...
PMID:Herbal hepatotoxicity. 1201 50

Genetic alterations associated with human hepatocellular carcinoma (HCC) have been reported previously, but are not sufficient to specify differences of HCCs from precancerous diseases of the liver, such as hepatitis, hepatic fibrosis, and cirrhosis. In the present study, we performed differential gene display analysis (DGDA) to clarify the specific genetic alterations associated with gene expression changes in the course of development of HCC from chronic viral hepatitis. Four pairs of surgically resected HCCs and hepatitis tissues were investigated. We found 1,028 expression sequence tags (ESTs) that were decreased or increased in HCC tissues compared with hepatitis tissues in the same patient. Nucleotide sequencing showed that they included 55 EST clones in the GenBank database, which were considered candidates for specific messenger RNA (mRNA) expression alterations in HCCs. After excluding 9 ESTs that code mitochondrial DNA, we performed quantitative real-time reverse-transcription polymerase chain reaction (RT-PCR) for the 46 remaining EST clones. We found 8 mRNAs underexpressed in primary HCC tissues in 20 patients in higher percentages than found in previous studies, including 18 cases (90%) for aldolase B (ALDOB), 15 cases (75%) for carbamyl phosphate synthetase 1 (CPS1), albumin (ALB), plasminogen (PLG), and EST 51549, 13 cases (65%) for cytochrome P450 subfamily 2E1 (CYP2E1), 12 cases (60%) for human retinol-binding protein 4 (RBP4), and 11 cases (55%) for human organic anion transporter C (OATP-C) gene. In conclusion, underexpression of key gene products may be important in the development and/or progression of HCC.
 ...
PMID:Underexpression of mRNA in human hepatocellular carcinoma focusing on eight loci. 1214 53


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>