Pharmacokinetics of ibuprofen enantiomers in rats after intravenous and oral administration of ibuprofen arginate / 药学学报

The pharmacokinetics of ibuprofen enantiomers were studied in rats after intravenous and oral administration of ibuprofen arginate by means of a chiral HPLC method. The pharmacokinetics of ibuprofen was stereoselective after intravenous and oral administration of ibuprofen arginate. The pharmacokinetic stereoselectivity was higher after oral administration than that after intravenous administration. The systematic (R)-(-)-to-(S)-(+) inversion might be more important than the presystematic one in the stereoselective pharmacokinetics after oral administration. Oral administration of ibuprofen arginate resulted in a very rapid absorption of (S)-(+)-ibuprofen (eutomer), and the absolute bioavailabilities of (S)-(+)-ibuprofen and (R)-(-)-ibuprofen were about 100% and 80%, respectively. Based on the systemic exposure of (S)-(+)-ibuprofen, it could be concluded that the pharmacological actions might be similar when ibuprofen arginate was given orally and intravenously, except some differences in the onset of action.

Metabolic pathways of dipfluzine in rats / 药学学报

<p><b>AIM</b>To investigate the metabolic pathways of dipfluzine in rats.</p><p><b>METHODS</b>After an oral dose of dipfluzine (80 mg x kg(-1)) to rats, urine was collected for 12 h. The metabolites of dipfluzine in urine were chromatographed and identified by LC/DAD/MS methods.</p><p><b>RESULTS</b>In the rat urine, there were 1-(4-fluorophenyl)-4-piperazinylbutanone and its glucuronide, 4-hydroxybenzophenone and its glucuronide, 4-fluoro-gamma-hydroxybenzenebutanoic acid and its glucuronide and sulfate, diphenylmethanol and its glucuronide, dipfluzine, and benzophenone.</p><p><b>CONCLUSION</b>In rats, dipfluzine was mainly metabolized in the pathways of N-desalkylation at 1- and 4-positions of piperazine ring. Some of metabolites were further conjugated with glucuronic acid and/or sulfuric acid.</p>

Gender-related differences in metabolism of the enantiomers of trans tramadol and trans O-demethyltramadol in rat liver microsomes / 药学学报

<p><b>AIM</b>To investigate the gender-related differences in the metabolism of trans tramadol (trans T) enantiomers and the glucuronidation of trans O-demethyltramadol (M1) enantiomers.</p><p><b>METHODS</b>In vitro, trans T or M1 were separately incubated with liver microsomes of male or female rats. The concentrations of the enantiomers of trans T and M1 were determined by an HPCE method.</p><p><b>RESULTS</b>Compared with (+)-enantiomers, (-)-trans T was preferentially metabolized, and (-)-M1 was produced faster in rat liver microsomes. (+)-M1 and (-)-M1 were preferentially glucuronidated in the liver microsomes of male and female rats, respectively. Compared with those in male rat liver microsomes, the enantiomeric ratios of CLint for M1 formation and M1 glucuronidation were more deviated from 1 in female rat liver microsomes.</p><p><b>CONCLUSION</b>In vitro, trans T metabolism, M1 formation and M1 glucuronidation were found to be stereoselective in rat liver microsomes. There were gender-related differences in the stereoselectivity in M1 formation and M1 glucuronidation, with a larger extent in female rat liver microsomes.</p>

Stereoselectivity in absorption of trans tramadol in rat intestine / 药学学报

<p><b>AIM</b>To investigate the stereoselectivity in absorption of trans tramadol (trans T) in rat intestine.</p><p><b>METHODS</b>The duodenum, jejunum and ileum were separately perfusated in situ with trans T dissolved in Krebs-Ringer buffer. Trans T enantiomers in the perfusate were analyzed with a high performance capillary electrophoresis (HPCE) method.</p><p><b>RESULTS</b>The absorbed fractions of trans T enantiomers were similar among the different segments of the rat intestine. The absorbed fraction of (+)-trans T was lower than that of (-)-trans T when the concentration of trans T was not higher than 40 mumol.L-1. As the concentration of trans T increased, the absorbed fractions of trans T enantiomers were reduced and the difference in absorbed fractions between trans T enantiomers became not significant.</p><p><b>CONCLUSION</b>Trans T enantiomers can be absorbed in different parts of the rat intestine. The intestinal absorption of trans T was stereoselective, (-)-trans T being preferentially absorbed.</p>

Stereoselectivity in biliary excretion of trans tramadol and trans O-demethyltramadol in rats / 药学学报

<p><b>AIM</b>To investigate the stereoselectivity in biliary excretion of trans tramadol (trans T) and trans O-demethyltramadol (M1) in rats.</p><p><b>METHODS</b>After a single intravenous dose of trans T hydrochloride (10 mg.kg-1) or M1 (2.5 mg.kg-1) to rats, the bile was collected for 30 min, then, blood was obtained from the heart. The enantiomers of trans T, M1 and M1 conjugated with glucuronic acid (M1c) in the bile and plasma were analyzed by high performance capillary electrophoresis (HPCE).</p><p><b>RESULTS</b>After the rats were given trans T, the bile concentrations of (+)-trans T were higher than those of (-)-trans T, and the (+)/(-)-trans T ratios were lower compared with those in the plasma. After the rats were given M1, the bile concentrations of (+)-M1 were higher than those of (-)-M1, and the bile concentrations of (+)-M1c were lower than those of (-)-M1c. The glucuronidation rate of (+)-M1 was lower than that of (-)-M1 in the bile.</p><p><b>CONCLUSION</b>The biliary excretion of trans T and M1 was stereoselective, (+)-trans T and (-)-M1 being preferentially excreted.</p>

Stereoselectivity in O-demethylation of trans tramadol in rat liver microsomes in vitro / 药学学报

<p><b>AIM</b>To study the stereoselectivity in O-demethylation of trans tramadol.</p><p><b>METHODS</b>With or without quinine and quinidine as inhibitors, rat liver microsomes were incubated in vitro with the enantiomers or the racemate of trans tramadol. The concentrations of the enantiomers of trans tramadol and O-demethyltramadol in the incubates were determined by high performance capillary electrophoresis. The O-demethylation processes were assayed by using the enzyme kinetic analysis method.</p><p><b>RESULTS</b>After incubation, the concentrations of (-)-O-demethyltramadol were higher than those of (+)-enantiomer in all rat liver microsomal incubates. Enzyme kinetic analysis showed that the Km of the formation of the enantiomers of O-demethyltramadol were similar; The Vmax and Clint of the formation of (-)-O-demethyltramadol were significantly higher than those of the formation of (+)-enantiomer. When the racemate of trans tramadol was used as the substrate, there was interaction between the two enantiomers. The Km of the formation of the enantiomers of O-demethyltramadol increased, the Vmax of the formation of (+)-O-demethyltramadol decreased, the Vmax of the formation of (-)-O-demethyltramadol increased slightly. The O-demethylation of the enantiomers of trans tramadol was shown to be inhibited competitively by quinine and quinidine. The Ki of quinine and quinidine were 1.6 and 10.8 mumol.L-1 to the formation of (-)-O-demethyltramadol, 0.8 and 3.4 mumol.L-1 to the formation of (+)-O-demethyltramadol, respectively. Furthermore, quinine and quinidine were found to have stereoselective inhibition on the formation of O-demethyltramadol, both mainly inhibited the formation of (+)-O-demethyltramadol.</p><p><b>CONCLUSION</b>The O-demethylation of trans tramadol was found to be stereoselective in rat liver microsomes in vitro, preferentially metabolized (-)-enantiomer. The stereoselectivity could be influenced by the interaction between the two enantiomers and the enzyme selective inhibitors.</p>

Mornitoring of the enantiomers of (?) -trans tramadol andits active metabolite in the serum of postoperative patients afterdifferent intravenous doses of (?)-trans tramadol hydrochloride injection / 中国临床药理学与治疗学

Aim To investigate the relationship between the clinical actions and the serum concentrations of the enantiomers of (?)-trans tramadol and its active metabolite. Methods 20 postoperative patients were divided into two groups and given multiple intravenous doses of (?)-trans tramadol hydrochloride injection, 400 mg?d-1 (group A) or 300 mg?d-1 (group B). The blood samples were taken at 38 h after the initial dose. The concentrations of the enantiomers of (?)-trans tramadol and its active metabolite, (?)-trans O-demethyltramadal were determined with high performance capillary electrophoresis(HPCE). Results The concentrations of the enantiomers of (?)-trans tramadol, the frequency and serious level of adverse reactions were higher in group A than in group B. The concentrations of the enantiomers of (?)-trans O-demethyltramadal, the analgesic effect were similar between group A and group B. Conclusion There is much closer relation between the analgesic effect and the concentration of (+)-O-demethyltramadal. The frequency and serious level of adverse reactions may be attributed to the higher concentrations of the enantiomers of (?)-trans tramadol, which are caused by the saturated metabolism.