- Impurity A and impurity B of midazolam or pharmaceutical composition thereof and application thereof
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The invention belongs to the field of medical chemistry, and particularly relates to an impurity A and an impurity B of midazolam or a pharmaceutical composition of midazolam and a preparation methodthereof, and application of the impurity A and the impur
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- Prediction of metabolic clearance using fresh human hepatocytes: Comparison with cryopreserved hepatocytes and hepatic microsomes for five benzodiazepines
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1. Predictions of in vivo intrinsic clearance from cryopreserved human hepatocytes may be systematically low. In the current study, the metabolite kinetics of a series of CYP3A4 substrates (benzodiazepines) in fresh human hepatocytes from five donors, via a major UK supplier, were investigated and compared with those previously reported (by the authors' laboratory) for cryopreserved human hepatocytes and hepatic microsomes. 2. A high incidence of autoactivation (up to tenfold) and heteroactivation (by testosterone, up to 14-fold) among the major pathways was observed. CYP capacity (Vmax) was marginally lower and 'affinity' constants (KM, S50) were marginally greater compared with cryopreserved hepatocytes. 3. Average intrinsic clearance (based on maximal clearance, CLmax) was sevenfold lower than in cryopreserved hepatocytes (reflecting sensitivity of intrinsic clearance estimation in vitro to mechanistic parameter values, particularly those involving atypical kinetics), but scaled intrinsic clearances for fresh (and cryopreserved) hepatocytes were within the range previously determined in hepatic microsomes. 4. There was no evidence from this series of studies that fresh hepatocytes provide quantitatively improved estimates of intrinsic clearance over cryopreserved hepatocytes.
- Hallifax,Galetin,Houston
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p. 353 - 367
(2008/12/21)
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- Differential induction of midazolam metabolism in the small intestine and liver by oral and intravenous dexamethasone pretreatment in rat
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1. Midazolam is metabolized in the rat by CYP3A enzymes to 4-OH-midazolam (4-OH-MDZ) and 1′-OH-midazolam (1′-OH-MDZ). The induction of midazolam metabolism was studied in male Wistar rats treated with dexamethasone (50mg kg-1 day-1) during 4 days via the oral or intravenous routes. Microsomes were prepared from the liver and the proximal small intestine and in vitro metabolism of midazolam was determined. In addition, CYP3A1- and CYP3A2-like protein levels were measured by gel electrophoresis and immunoblotting. 2. The Vmax's (mean SEM) for 4-OH-MDZ and 1′-OH-MDZ formation were much lower in intestinal (0.078 ± 0.002 and 0.074 ± 0.002 μM min-1 mg-1 protein, respectively) compared with hepatic microsomes prepared from the uninduced rat (0.870 ± 0.007 and 0.310 ± 0.020 μmin-1 mg-1 protein, respectively). Induction by oral or intravenous dexamethasone pretreatment led to significant increases in Vmax for 4-OH-MDZ and 1′-OH-MDZ by both intestinal and hepatic microsomes. Oral dexamethasone pretreatment via the oral route resulted in a more pronounced increase in Vmax compared with intravenous administration of the inducer. 3. CYP3A1 and CYP3A2 protein levels in liver microsomes were significantly increased following oral (3.7- and 3.2-fold, respectively) or intravenous (2.6- and 2.1-fold, respectively) pretreatment with dexamethasone. On the contrary, only oral dexamethasone pretreatment resulted in a significant change in intestinal CYP3A2-like protein (7.3-fold). A slight difference in the migration distance of the immunoreactive band for CYP3A2 was also observed for intestinal microsomes. 4. These results suggest that intestinal CYP3A enzymes in the rat differ from hepatic CYP3A1 and CYP3A2. They also demonstrate that systemic dexamethasone administration can induce intestinal microsome activity.
- Eeckhoudt,Horsmans,Verbeeck
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p. 975 - 984
(2007/10/03)
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- In vitro hepatic metabolism of CYP3A-mediated drugs quinine and midazolam in the common brush-tailed possum (Trichosurus vulpecula)
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This report characterizes the P450 isoenzymes involved in quinine metabolism in liver microsomes of the common brush-tailed possum (Trichosurus vulpecula). The mean maximal velocity (V(max)) for 3-hydroxyquinine formation in possum livers was 1,512 ± 510 pmol/mg protein/min (males) and 1,680 ± 690 pmol/mg protein/min (females). The mean V(max) value for 3-hydroxyquinine formation in possums was approximately threefold higher than that found in human livers. The mean apparent Michaelis constant (K(m)) for 3- hydroxyquinine formation in possum livers was 31.9 ± 16 μM in males and 16.1 ± 5 μM in females. At low concentrations of quinine (40 μM), the quinine 3-hydroxylation was inhibited more than 90% by midazolam, 60% by troleandomycin, 40% by erythromycin, and 47% by nifedipine, all of which are CYP3A inhibitors. Other inhibitors for CYP2C9/10, CYP2D6, CYP2E1, and CYP1A1/2 showed little or no inhibition effect on 3-hydroxylation of quinine. Xenobiotic inhibition studies suggest that the liver CYP3A enzyme family or one similar to human liver CYP3A is responsible for 3-hydroxylation of quinine in possum livers. The metabolism of midazolam to 1'-hydroxy and 4- hydroxy metabolites was also studied. The in vitro metabolism of midazolam was found to be much lower in possum liver microsomes as compared to that observed in human liver microsomes. The mean V(max) values for 4-hydroxy- and 1'-hydroxymidazolam in male possums were 179 ± 53 and 479 ± 333 pmol/mg protein/min, respectively. For female possums, the mean V(max) values were 235 ± 31 and 671 ± 143 pmol/mg protein/min, respectively. These V(max) values for male possums were 23 and 8 times less (17 and 6 times less for female possums), respectively, than those observed with human liver microsomes. The present study has demonstrated that, although possums are able to metabolize both midazolam and quinine, the capacity to metabolize midazolam is considerably lower in possum livers than in human livers. This finding could be useful for the selection of alternative poisons to control populations of possums.
- Ho, Ping-Chuen,Luo, Xiao-Xing,Macauley, Jackie S.,Grigor, Murray R.,Wanwimolruk, Sompon
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p. 317 - 324
(2007/10/03)
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- Imidazodiazepines and processes therefor
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Novel Imidazobenzodiazepines and their analogs are useful as anticonvulsants, muscle relaxant, anxiolytic and sedative agents. Preferred compounds of this class belong to the imidazo[1,5-a][1,4]diazepine series which may have a very wide variety of organic substituents. An especially preferred genus included within the purview of the invention encompasses a compound of the formula STR1 wherein R1 is hydrogen and lower alkyl preferably methyl; R3 and R5 are hydrogen; R4 is hydrogen, nitro and halogen, most preferably, chlorine, and in a most preferred embodiment when positioned on the fused benzo portion of the imidazobenzodiazepine is in the 8-position thereof, R6 is phenyl or halo, nitro, or lower alkyl-substituted phenyl, preferably, halo, with fluorine being the preferred halogen, the substituted fluoro being positioned in the 2-position of the phenyl moiety and R2 is hydrogen and lower alkyl.
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- Simultaneous determination and pharmacokinetics of midazolam and its hydroxymetabolites in plasma and urine of man and dog by means of high-performance liquid chromatography
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A HPLC (high performance liquid chromatography) method for the determination of 8-chloro-6-(2-fluorophenyl)-1-methyl-4H-imidazo[1,5-a][1,4]benzodiazepine (midazolam, Ro 21-3981, Dormicum) and its hydroxy metabolites has been developed. The half-life of elimination of midazolam and the glucuronides of the metabolites 1-hydroxymethyl-midazolam, 4-hydroxy-midazolam and 1-hydroxymethyl-4-hydroxy-midazolam are identical, 53 min in dogs and 90 min in man.
- Vree,Baars,Booij,Driessen
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p. 2215 - 2219
(2007/10/02)
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