A polarographic method for the determination of the N-oxide, N-oxide-sulphoxide and sulphoxide metabolites of chlorpromazine

Synthesis of the N-oxides of phenothiazine antipsychotic agents

Chlorpromazine N-oxide, fluphenazine N4'-oxide, prochlorperazine N4'-oxide, sulforidazine N-oxide, and trifluoperazine N4'-oxide were synthesized by oxidation of the designated nitrogen atom in the N-10 side chain of the respective parent drug with 3-chloroperoxybenzoic acid. In the case of trifluoperazine, a stepwise increase in the amount of oxidant yielded the N1',N4'-dioxide and N1',N4',S-trioxide. The N',S-dioxides of chlorpromazine and sulforidazine were obtained by hydrogen peroxide oxidation of the appropriate parent drug.

Determination of plasma nefopam by liquid chromatography and electrochemical detection

A liquid chromatographic method for the determination of plasma nefopam is presented. A combination of liquid- and solid-phase extraction and electrochemical detection gave clean extracts and, hence, a low limit of detection. Calibration curves were linear over at least two orders of magnitude (1-100 ng/ml) making the method suitable for pharmacokinetic studies.

Ionization constants, octanol partition coefficients and cholinesterase inhibitor constants for chlorpromazine and its metabolites

The relationship between the lipophilic character of chlorpromazine and seven of its metabolites and their ability to inhibit horse serum cholinesterase (Ki) has been investigated. Log(1/Ki) values were correlated with log P octanol partition coefficients (r = 0.88, P less than 0.01, n = 8). The inhibitor values ranged from 2.7 x 10(-6) M for chlorpromazine to 48.6 x 10(-6) M for monodesmethylchlorpromazine sulphoxide. Ionization constants were determined by limiting solubility, spectrophotometry and pH-partition characteristics. Demethylated metabolites were more basic than the tertiary amines and the sulphoxides were slightly less basic than the corresponding sulphides.

Chromatographic separation of thioridazine sulphoxide and N-oxide diastereoisomers: identification as metabolites in the rat

(+/-)-Thioridazine and (+/-)-desmethylthioridazine have been oxidized to produce a number of chiral sulphoxide and amine oxide compounds. Diastereoisomeric isomers were separated by thin-layer and high performance liquid chromatography. Thioridazine-5-sulphoxide, N-desmethylthioridazine-5-sulphoxide and thioridazine-N-oxide diastereoisomers were found to be thioridazine metabolites following dosing in rats or after in-vitro incubation with rat liver homogenate.

Metronidazole-induced myocardial depression: chemical and pharmacological studies on the role of calcium in-vitro

The interaction of metronidazole with calcium to form a water-soluble complex has been studied by titration with ethylenediaminetetraacetate (EDTA), direct current and pulse polarographic reduction steps of the nitro-group at pH 5 and 7, and by ultraviolet absorption. Stoichiometric calculations, X-ray powder diffraction pattern of the synthesized metronidazole-calcium complex, and molecular ion peak at m/z 381 in the mass spectrum of this product, showed that a 2:1 complex is formed. The interaction of metronidazole with calcium on myocardial contractile performance of guinea-pig electrically-driven isolated left atria in physiological solution was also examined. Metronidazole induced a sustained, concentration-dependent depression of the tension that was reversed by changing the bathing fluid to physiological solution, and/or by adding excess calcium ion. The drug-induced negative inotropic response was antagonized competitively by increasing calcium ion in the bath, whereas noradrenaline antagonized metronidazole-induced negative inotropic responses non-competitively. Addition of the metronidazole-calcium complex to the bath did not affect normal myocardial contractile performance. The results show that metronidazole produces a direct negative inotropic effect on isolated atrial muscles by interfering with Ca2+, and by preventing Ca2+ function in the events leading to contractile activity of atrial muscles.

A TLC fluorescence derivatization assay for chlorpromazine and its non-conjugated hepatic microsomal metabolites

Procedures for the assay of chlorpromazine (CPZ) and its metabolites were compared. An improved assay, involving organic extraction, thin-layer chromatography and fluorescence derivatization, was developed. The compounds were extracted from microsomal protein suspensions into 15% n-propanol in dichloromethane by successive extractions at pH 2 and pH 12. CPZ and its mono- and di-desmethyl, 7-hydroxy, N-oxide, sulphoxide and N-oxide-sulphoxide metabolites were separated using TLC on silica gel developed with methanol-acetone-ammonia (50:50:1 v/v/v). The compounds were extracted from the TLC plate with chloroform-methanol (2:1 v/v) and subjected to oxidation with hydrogen peroxide. The highly fluorescent oxidized derivatives were identified as sulphoxides by their fluorescence characteristics. Amounts of derivatized CPZ and metabolites were measured using derivatized promazine as the internal standard.

Quantitation of the antineoplastic agent indicine-N-oxide in human plasma by differential pulse polarography

A sensitive and reproducible differential pulse polarographic method of analysis was developed for indicine-N-oxide (NSC 132319) in human plasma. Lyophilized plasma is extracted with methanol, and the extract is chromatographed over partially deactivated aluminum oxide and reversed-phase silica gel columns. Indicine-N-oxide is eluted from the silica gel column with 25% aqueous methanol and quantitated by differential pulse polarography by measurement of the peak current at -0.72 +/- 0.03 v (versus the saturated calomel electrode). Recovery of indicine-N-oxide from plasma was 88 +/- 7% (SD) in the 1-20-microgram/ml range. The method was linear over the range of 0.5-10 microgram/ml of pH 4.6 buffer.