Leaching of antioxidants and vulcanization accelerators from rubber closures into drug preparations.

A thin-layer chromatographic method was used to highlight the leaching into drug preparations of several constituents of elastomeric closures. Among the 150 preparations analysed, the twenty-eight local anaesthetics presented in single-dose delivery syringe-cartridges, one Epinephrine injection in prefilled syringes, eight insulin preparations and two Prednisolone acetate suspensions in the form of small volume flasks (less than or equal to 20 ml) were contaminated by one or more of the following: 2-mercaptobenzothiazole (MBT), 2-mercaptobenzothiazole disulphide and 2-mercaptobenzimidazole (MBI). Prednisolone acetate suspensions also contained 2,2'-methylene-bis(4-methyl-6-alpha-methylcyclohexylphenol). No contamination was found in drug preparations presented in large volume flasks (250-1000 ml). 2-(2-Hydroxyethylthio)-benzothiazole was not present, which indicated that the rubbers had not been sterilized with ethylene oxide. Elastomeric parts of drug closures analysed in the same way contained the same compounds as those found in drugs, one case excepted, which confirms the origin of the contamination. The lowest and the highest concentrations were found in syringe-cartridges; they ranged from 8.3 to 13.8 micrograms ml-1 for MBT, from 2.9 to 9.3 micrograms ml-1 for MBTS and from 2.8 to 11.1 micrograms ml-1 for MBI. Variable results were obtained, for a same preparation, depending upon the batches analysed, which indicates that rubber formulations and/or vulcanization conditions differed. The allergenic, toxic, embryotoxic and mutagenic properties of the compounds leached are discussed.

Influence of time and chloride ions on the interaction of cisplatin with human albumin in-vitro.

The interaction of cis-dichlorodiammineplatinum (II) (cisplatin) with human serum albumin (HSA), dissolved in phosphate buffer with or without sodium chloride (0.1 M) has been examined at pH 7.4 and mu = 0.154. Equal volumes of cisplatin and HSA solutions were incubated at 37 degrees C for various times and filterable platinum concentrations versus time measured by flameless atomic absorption spectrophotometry. Binding kinetics differed depending on the buffer solutions used and on the time elapsing between cisplatin dissolution and outset of incubation with HSA. Experimental data were fitted to a theoretical equation used to calculate the number of nucleophilic sites per HSA molecule. Titrations of the HSA sulphydryl group content before and after incubation with a cisplatin solution were made, from which it was shown that the lone SH-group of the HSA macromolecule is involved in cisplatin binding. We also studied HSA's sensitivity towards denaturing agents when it was complexed with cisplatin. This sensitivity was decreased upon cisplatin binding. Also, the binding capacities of HSA and the HSA-Pt(II) complex to both tryptophan and warfarin were compared to determine the possible influence of cisplatin upon the binding to HSA of other drugs; this influence was negligible.

[Characterization by thin layer chromatography of benzothiazole derivatives and beta-sitosterol leached by disposable syringes]. / Caractérisation par chromatographie sur couche mince des composés benzothiazoliques et du beta-sitostérol cédés par les seringues non réutilisables.

A thin-layer chromatographic study of 2-mercaptobenzothiazole, 2-(methylthio)benzothiazole, 2-(2-hydroxy-ethylthio)benzothiazole, 2-hydroxybenzothiazole, zinc 2-mercaptobenzothiazolate, mercaptobenzothiazole disulfide, and beta-sitosterol with three developing solvents and eleven spray reagents is reported. A simple method is described which highlights the leaching of 2-mercaptobenzothiazole and 2-(2-hydroxy-ethylthio)benzothiazole from the rubber plunger-seals of disposable syringes: contact of rubber with bidistilled water, extraction of this liquid with chloroform, chromatography on silica gel with the solvents previously studied and spraying with N-chloro-2,6-dichloro-p-benzoquinone monoimine. The method may also be used to discriminate those syringes sterilized with ethylene oxide, the only ones able to leach 2-(2-hydroxy-ethylthio)benzothiazole, from those sterilized by irradiation. Owing to the beta-sitosterol traces leached, it may also be used to investigate whether the plunger-seals are made of natural rubber. The toxic effects of the compounds leached are briefly reported.

In vitro mechanism study of microtubule assembly inhibition by cis-dichlorodiammine-platinum(II).

The inhibitions of microtubule protein (MTP) and tubulin 6S polymerizations by cis-dichlorodiammine-platinum(II) (CDDP) have been investigated by turbidity measurements and electron microscopy. For 2.5 X 10(-4) M CDDP after 40 min contact time at 27 degrees, the inhibition was 60% for MTP (1.2 mg/ml) and nearly 90% for tubulin 6S (1.2 mg/ml). Microtubules were not present after a 1 hr contact time at 27 degrees with 2.5 X 10(-4) M CDDP. Free sulfhydryl group determinations with 5,5'-dithio-bis-(2-nitrobenzoate) (DTNB) showed that 20.10 (+/- 0.05) sulfhydryl groups were found per tubulin dimer. In the presence of excess CDDP, this number was reduced to 17.74 (+/- 0.05) after a 1 hr contact time at 27 degrees. By using CDDP-tubulin dialysis assays, the CDDP-tubulin complex formation was found to be an irreversible reaction through a covalent binding at the sulfhydryl group sites. By the DEAE filter paper method, CDDP was shown to slightly decrease vinca-alkaloid and colchicine bindings to tubulin likely by inducing a conformational change of the protein.

In vitro plasma binding of some second generation antitumor platinum complexes.

The kinetics of five cisplatin analogs binding to human plasma fractions possessing a molecular weight greater than 50,000 daltons were studied. Each drug solution in plasma ultrafiltrate or phosphate buffer (pH = 7.4, mu = 0.154) was mixed with human plasma and filterable platinum concentrations were measured versus time by atomic absorption spectrophotometry. The only Pt IV compound studied did not bind. All the other Pt II complexes bound, but their binding kinetics were quite different. The experimental data were fitted to a theoretical equation based on the hypothesis that plasma nucleophilic agents possessing a molecular weight greater than 50,000 daltons are able to react with Pt compounds with an apparent second order rate constant. The apparent reaction rate constants and initial concentrations of these nucleophilic agents were calculated. The difference between the respective values obtained for each cisplatin analog could be explained by differences in their chemical formulas. Therefore our result should contribute towards a better understanding of the pharmacokinetics of the cisplatin analogs studied.