Drugs online research references
Br J Clin Pharmacol. 1996 Feb;41(2):149-56.
Venlafaxine oxidation in vitro is catalysed by CYP2D6.
Otton SV, Ball SE, Cheung SW, Inaba T, Rudolph RL, Sellers EM.
Clinical Research and Treatment Institute, Addiction Research Foundation, Toronto, Ontario, Canada.
1. Several selective 5-HT reuptake inhibitors (SSRIs) are inhibitors of the genetically polymorphic drug metabolizing enzyme, CYP2D6. We studied the interaction of venlafaxine, a new SSRI, with CYP2D6 in human liver microsomes. 2. Venlafaxine was a less potent inhibitor of this enzyme activity in vitro than other SSRIs tested. The average apparent Ki values determined using CYP2D6-dependent dextromethorphan O-demethylation were: 33, 52 and 22 microM for rac-venlafaxine, R(+)-venlafaxine and S(-)-venlafaxine, respectively, vs 0.065 to 1.8 microM for paroxetine, fluoxetine, norfluoxetine, fluvoxamine and sertraline. 3. Microsomes from human livers (n = 3) and from yeast transformed with an expression plasmid containing human CYP2D6 cDNA catalyzed the O-demethylation of venlafaxine, which is the major metabolic pathway in vivo. Intrinsic metabolic clearance values (Vmax/Km) indicated that S(-)-venlafaxine was cleared preferentially via this pathway. 4. In microsomes from CYP2D6-deficient livers (n = 2), Vmax/Km of O-demethylation of venlafaxine was one to two orders of magnitude lower and was similar to the rate of N-demethylation. 5. Studies with chemical probes which preferentially inhibit P450 isoforms suggested that CYP3A3/4 is involved in venlafaxine N-demethylation. 6. These in vitro findings predict phenotypic differences in the kinetics of venlafaxine in vivo, although the clinical importance of this is unclear as O-demethylvenlafaxine is pharmacologically similar to the parent drug. The findings also predict relatively limited pharmacokinetic interaction between venlafaxine and other CYP2D6 substrates.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8838442&dopt=Abstract
kwd match effexor online literature
J Chromatogr B Biomed Sci Appl. 1998 Feb 13;705(2):303-8.
Simultaneous measurement of venlafaxine and its major metabolite, oxydesmethylvenlafaxine, in human plasma by high-performance liquid chromatography with coulometric detection and utilisation of solid-phase extraction.
Clement EM, Odontiadis J, Franklin M.
University of Oxford, Department of Psychiatry, Warneford Hospital, UK.
Venlafaxine, oxydesmethylvenlafaxine and an internal standard (paroxetine) were extracted from plasma by a solid-phase extraction technique. Chromatography was performed using isocratic reversed-phase high-performance liquid chromatography (HPLC) with coulometric endpoint detection. The standard curves were linear over the range 0-200 ng/ml for both venlafaxine and oxydesmethylvenlafaxine in plasma. The mean inter- and intra-assay coefficients of variation over the range of the standard curves were less than 10%. The absolute recovery averaged 74% for venlafaxine and 67% for oxydesmethylvenlafaxine. The sensitivity was 0.5 ng for both the analytes. Plasma profiles of the analytes following oral administration of venlafaxine, are presented.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9521568&dopt=Abstract
kwd match effexor online literature
J Anal Toxicol. 1997 Mar-Apr;21(2):166-9.
Comparison of analytical methods in the determination of two venlafaxine fatalities.
Long C, Crifasi J, Maginn D, Graham M, Teas S.
Saint Louis University School of Medicine, Department of Pathology, Berkeley, Missouri 63134, USA.
Two venlafaxine (Effexor)-related deaths are reported with comparison of results from the analysis of specimens using capillary gas chromatography with a nitrogen-phosphorous detector (GC-NPD) and high-performance liquid chromatography (HPLC) using a UV-vis detector. Blood concentrations in Case 1 were 7.27 micrograms/mL venlafaxine and 5.03 micrograms/mL O-desmethylvenlafaxine, and Case 2 had 89.67 micrograms/mL venlafaxine with 3.44 micrograms/mL of the desmethyl metabolite. A comparison of analytical methods and specimen concentration is presented.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9083836&dopt=Abstract
kwd match effexor online literature
online pharmacies ||
Hair Million herbal formula for hair loss and hair growth ||
Tramadol ||
Antibiotics and prescription medications online literature ||
Antibiotics