Selective determination of tolbutamide in pharmaceutical dosage forms by reaction with ninhydrin

Effect of food and tablet age on relative bioavailability and pharmacodynamics of two tolbutamide products

Relative bioavailability and pharmacodynamics of tolbutamide from two different commercially available tablet products have been evaluated in healthy subjects in a single-dose crossover study. "Fresh" tablets and tablets aged by exposure to 98% relative humidity for 3 d at ambient temperature were studied. Aging was found to differentially affect both the rate and extent of absorption for the two products. Differences were reflected by log AUC (generic product AUC 10% lower than the product of the innovator, p = 0.047), peak concentration (generic product 27% lower than the product of the innovator, p = 0.0001), mean absorption time (generic product 119% longer than the product of the innovator, p = 0.0008), and mean residence time (generic product 17% longer than the product of the innovator, p = 0.011). Aged product from the innovator produced statistically significantly higher serum tolbutamide concentrations for the first 8 h postdose and a greater glucose depression than aged generic product. Administration of unaged tablets with food produced differences in the rate of absorption, manifested in time-to-peak (generic product 69% later than the product of the innovator, p = 0.006), peak concentration (generic product 18% lower than the product of the innovator, p = 0.001), and mean absorption time (generic product 104% greater than the product of the innovator, p = 0.007), which resulted in statistically significantly higher tolbutamide concentrations for the product of the innovator than for the generic product for the first 3 h postdose.(ABSTRACT TRUNCATED AT 250 WORDS)

Determination of gliclazide in human serum by high-performance liquid chromatography using an anion-exchange resin

A method for the routine clinical examination of serum gliclazide by high-performance liquid chromatography (HPLC) on a column packed with a macroporous anion-exchange resin, Diaion CDR-10, was developed. The elution was performed with acetonitrile-methyl alcohol-1.2 M ammonium perchlorate (4:3:7, v/v/v) at a flow-rate of 0.4 ml/min. The retention time of gliclazide was 15 min. It seems that the retention mechanism of gliclazide under the HPLC conditions described is not only ion-exchange mode but reversed-phase mode between the anion-exchange resin and the mobile phase. The detection limit of gliclazide was 0.2 microgram/ml in plasma. The coefficient of variation for the within-day assay was 5.0% (0.2 microgram/ml, n = 8). The decay curve of serum gliclazide in diabetic patients was determined.

Stability-indicating high-performance liquid chromatographic determination of chlorpropamide, tolbutamide, and their respective sulfonamide degradates

A quantitative high-performance liquid chromatographic method for the determination of chlorpropamide, tolbutamide, and their respective hydrolysis products, p-chlorobenzenesulfonamide and p-toluenesulfonamide, in solid dosage forms was developed. The method is stability indicating and can be used to determine the sulfonamide hydrolysis product and the intact drug in the presence of minor degradates. Method reproducibility, demonstrated by repeated injections of a calibration standard, was 1.21%. The lower limit of quantitation of the hydrolysis products, p-chlorobenzenesulfonamide and p-toluenesulfonamide, was 0.2 microgram/5-microliter injection. The accuracy of the method for intact drugs was determined by comparison of the HPLC results to those obtained by the appropriate USP or BP assays. The mean of the results obtained by the two methods differed by 0.7% for chlorpropamide and 0.3% for tolbutamide. Pure drug samples were spiked with amounts of the hydrolysis products ranging from 20 to 120% of the intact content. The mean percent recovery for p-chlorobenzenesulfonamide was 98.6%; for p-toluenesulfonamide, it was 100.6%. A qualitative TLC procedure for the detection of chlorpropamide, p-chlorobenzenesulfonamide, dipropylurea, propylurea, n-propylamine, tolbutamide, p-toluenesulfonamide, dibutylurea, butylurea, and n-butylamine is also described.

Determination of oral anti-diabetic agents in human body fluids using high-performance liquid chromatography

Two widely prescribed anti-diabetic agents for which no simple assay method was previously available can now be determined by high-performance liquid chromatography using a UV detection system. The two drugs investigated were tolbutamide (a sulphonylurea) and phenformin (a biguanide). Tolbutamide can be assayed directly, after a single extraction step, on a reversed-phase system, illustrating the simplicity of the technique for carrying out analyses on underivatised drug compared with gas chromatography. Phenformin was not so easily chromatographhed using straightforward partition systems; however, by the choice of a suitable ion-pair agent it was possible to chromatograph the underivatised drug in a relatively simple reversed-phase system.

Gas chromatographic and mass spectrometric analysis of the products of methylation of sulfonylurea drugs

Gas chromatographic analysis of the products of reaction of diazomethane with tolbutamide and chlorpropamide indicates the formation of three compounds in both cases. As expected, N-methylation (at sulfonamide nitrogen) is the predominant reaction; minor amounts of O-methylated product are also observed. The third product in both cases is the N-methylsulfonamide formed by decomposition of the N-methylated sulfonylurea during gas chromatography. Electron impact and chemulfonylurea during gas chromatography. Electron impact and chemical ionization mass spectrometric analysis, as well as 1H nuclear magnetic resonance examination of samples collected from gas chromatography, confirm the structural assignments. Additionally, proton magnetic resonance analysis of the crude reaction products established that N-methylsulfonamides are not formed in the course of the diazomethane reaction and that the O-methylated derivatives are true products of the reaction. The use of a paramagnetic shift reagent allowed direct estimation of the ratios of N- to O-methylation, and the demonstration that these ratios are not vitiated during gas chromatographic analysis.