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S Rudaz

Publications and source records attributed to S Rudaz.

30 records · Page 2Linked to original sources
PubMed1998

Use of cyclodextrins in capillary electrophoresis: resolution of tramadol enantiomers.

Capillary zone electrophoresis was successfully applied to the enantiomeric resolution of racemic tramadol. Both uncoated and polyacrylamide-coated capillaries were tested for method optimization using either negatively charged or native cyclodextrins (CD) added to the background electrolyte (BGE). The resolution was strongly influenced by the CD type and concentration as well as by the pH and the concentration of the BGE. Among the CDs tested, carboxymethylated-beta-cyclodextrin allowed the baseline separation of tramadol enantiomers. After the method was optimized, it was validated in a coated capillary for enantiomeric analysis of tramadol enantiomers in pharmaceutical formulation, including specificity and elution order, linearity, accuracy and precision, determination of limit of detection (LOD) and quantification (LOQ), enantiomeric purity linearity, freedom from interference, and stability of sample solutions. Precision at the target concentration was less than 2%, with an accuracy higher than 99%. Furthermore, the method was able to detect 0.3% and to quantify 1% of the minor enantiomer in the presence of the major one at the target value.

Analgesics, Opioid↗
PubMed1996

Stereoselective determination of methadone in serum by HPLC following solid-phase extraction on disk.

A solid-phase extraction (SPE) technique for methadone has been developed using a mixed-mode solid-phase extraction disk which contains both hydrophobic and cation-exchange functional groups. The SPE technique was used to isolate the drug from the biological matrix and to prepare a cleaner sample prior to stereoselective analysis by HPLC on a silica column with covalently bound alpha 1-acid glycoprotein (Chiral-AGP) followed by ultraviolet detection at 205 mm. The within-run precision was less than 5% for the complete method over the therapeutic range. The quantification limit was 25 ng ml-1. The between-run precision was less than 15% at the quantification limit. The between-run precision at other concentrations was less than 8.5% with an accuracy of more than 95%. The mean recovery for R-methadone was 78.5% and the mean recovery for S-methadone was 73.4%. The complete procedure has been validated. This method was successfully used for the analysis of 15 clinical cases.

Analgesics, Opioid↗
PubMed1996

Stereoselective interaction between piroxicam and acenocoumarol.

1. An open-label study was performed to assess the effect of piroxicam on the pharmacokinetics of acenocoumarol enantiomers. 2. Eight healthy male volunteers received an oral dose of 4 mg rac-acenocoumarol on days 1 and 8, plus 40 mg piroxicam orally 2 h before the anticoagulant on day 8. R- and S-acenocoumarol, piroxicam and their metabolites were measured in plasma over a 24 h interval. 3. The pharmacokinetics of R-acenocoumarol were markedly modified by piroxicam: Cmax+28.0% (s.d.23.8), P < 0.05; AUC(0, 24 h)+47.2% (21.5), P < 0.005; and t1/2 +38.0% (34.5), P < 0.01. A concomitant decrease of CL/F was observed: -30.8% (10.0), P < 0.0001. A similar, but statistically non-significant trend, was observed on the S-enantiomer: Cmax: +9.5% (s.d.36.6), AUC(0, 24 h): + 15.4% (23.4), t1/2: +19.9% (42.0), and CL/F: -9.8% (20.5). V/F remained unchanged for both enantiomers. 4. Piroxicam plasma AUC(0, 24 h) correlated closely with R- and S-acenocoumarol AUCs on day 1 (r = 0.901, P < 0.005 and r = 0.797, P < 0.05, respectively), as well as with the difference of AUC between days 1 and 8 for R-acenocoumarol (r = 0.903, P < 0.001) and S-acenocoumarol (r = 0.711, P < 0.05). 5. Piroxicam markedly reduced acenocoumarol enantiomer clearance, with a greater effect on the more active R-isomer. This interaction, which occurs in addition to the well documented pharmacodynamic one (effect on platelets), is expected to result in increased anticoagulant effect.

Acenocoumarol↗