Gas chromatographic determination of glibenclamide in plasma

A radioimmunoassay for determination of glibenclamide and other sulfonylureas

An antiserum was prepared for the determination of glibenclamide and for the estimation of other commercially available sulfonylureas. Rabbits were immunized with a glibenclamide-BSA conjugate. Tritiated glibenclamide was used as the tracer. The assay was performed in the presence of 8-anilinonaphthalenesulfonic acid to displace glibenclamide bound to serum protein, and free and antibody bound tracer were separated by dextran-coated charcoal. For glibenclamide determination in serum and plasma the limit of detection was 3 ng/ml. Sensitivity calculated for the whole determination range was 102 cpm for a 10 % concentration difference. Specificity studies showed a cross-reaction of less than 0.1 % for glibenclamide metabolite M1 and 9 % for metabolite M2. Other sulfonylurea drugs display cross-reactivities from 0.1% (chlorpropamide) to 190% (gliquidone). Both intra-assay and inter-assay imprecision were below 10 %. Accuracy was established by comparison of the present method with HPLC. The assay was applied to the specific determination of glibenclamide in clinical trials and for diagnosing factitious hypoglycemia caused by sulfonylureas.

Liquid chromatography tandem mass spectrometry method for simultaneous determination of antidiabetic drugs metformin and glyburide in human plasma

A simple and rapid liquid chromatography/tandem mass spectrometry (LC-MS/MS) method has been developed and validated for the simultaneous quantitation of antidiabetic drugs metformin and glyburide in human plasma using glimepiride as internal standard (IS). After acidic acetonitrile-induced protein precipitation of the plasma samples, metformin, glyburide and IS were chromatographed on reverse phase C18 (50 mm x 4.6 mm i.d., 5 microm) analytical column. Quantitation was performed on a triple quadrupole mass spectrometer employing electrospray ionization technique and operating in multiple reaction monitoring (MRM) and positive ion mode. The total chromatographic run time was 3.5 min and calibration curves were linear over the concentration range of 20-2500 ng/ml for metformin and 5-500 ng/ml for glyburide. The method was validated for selectivity, sensitivity, recovery, linearity, accuracy and precision, dilution integrity and stability studies. The recoveries obtained for the analytes and IS (>or=69%) were consistent and reproducible. Inter-batch and intra-batch coefficient of variation across four validation runs (LLOQ, LQC, MQC and HQC) was less than 8%. The accuracy determined at these levels was within +/-8% in terms of relative error (RE). The method was applied to a bioequivalence study of 500 mg metformin and 5mg of glyburide tablet after oral administration to 28 healthy human subjects under condition of fasting.

Diagnostic values of combined glucose and lactate values in cerebrospinal fluid and vitreous humour--our experiences

The final diagnosis of death in hypoglycaemic or diabetic coma should always be done as a synopsis of anamnestic response, morphology, biochemical (glucose, lactate, HBA1c, ketonic bodies, insulin, and C-peptide) and toxicological findings. High glucose levels in vitreous humour (more than 13 mmol/L, 234 mg/dL) or combined values of glucose and lactate in vitreous humour or in cerebrospinal fluid over threshold values of 23.7 mmol/L (427 mg/dL) and 23.4 mmol/L (422 mg/dL) respectively, can be an indicator of the pre-mortem hyperglycaemic state with fatal outcome. The determination of glycated haemoglobin, acetone and other ketone bodies improve the diagnostic values of the whole procedure. Diabetic ketoacidosis (blood acetone >0.3 g/L) is more often the cause of death of diabetic patients than the non-ketotic hyperosmolal state. Hypoglycaemia is deemed fatal if the combined values are lower than 5.5 mmol/L (100 mg/dL) and can not be excluded if they are lower than 8.9 mmol/L (160 mg/dL). Two cases of detected hypoglycaemia are described further. A psychiatric patient with diabetes (Hba1c 8.4%) committed suicide with an insulin overdose. The combined values of glucose and lactate in vitreous humour and in cerebrospinal fluid were 3.3 and 4.1 mmol/l, respectively. In another case a low combined glucose and lactate value (8.7 mmol/L) in vitreous humour indicated, besides the high concentration of glibenclamide (0.9 mg/L) in the blood of a driver with a poorly controlled diabetic condition (Hba1c = 10.6%), a state of decreasing blood glucose in the time before the accident causing the driver to feel un-well and behave inappropriately.

Pharmacokinetic and pharmacodynamic studies of glibenclamide in non-insulin dependent diabetes mellitus

1. The pharmacokinetic and pharmacodynamic properties of oral glibenclamide have been studied in 31 hospitalised in-patients and 79 ambulant out-patients with diabetes mellitus. 2. Breakfast was found to have no significant influence on the kinetic behaviour of glibenclamide or on the effect of this drug on blood glucose utilisation. 3. The time course of glibenclamide kinetics after 20 mg dosing was adequately described by a two-compartment open model, yielding mean half-lives of 3.3 +/- 1.5 h (t1/2, lambda 1) and 9.7 +/- 1.2 (t1/2, z) for the initial and terminal elimination phases respectively. 4. No significant accumulation or change in kinetic profile occurred in patients who had normal renal and hepatic function, were treated continuously with glibenclamide, and then rechallenged after 8-12 weeks. 5. Despite inter-individual variations in drug absorption, peak plasma concentrations (Cmax) and the area under the plasma concentration-time curve (AUC(0-24] were dose-dependent over the dose range 5-20 mg. No significant dose-response behaviour was observed in respect of glucose utilisation, suggesting that there is little clinical benefit in using doses of glibenclamide above 5 mg day-1. 6. Comparison of plasma glibenclamide concentrations at different time-bands following doses of 5 and 10 mg showed a wider range in ambulant out-patients than in age-, sex-matched in-patients treated with the same dosages of drug. Mean plasma drug concentrations attained at all time bands up to 8 h after dosing were higher in out-patients than in in-patients, suggesting a tendency to 'over-compliance' by patients in anticipation of attendance at clinic.

Simultaneous determination of the sulphonylurea glimepiride and its metabolites in human serum and urine by high-performance liquid chromatography after pre-column derivatization

A sensitive and selective high-performance liquid chromatographic method has been developed for a new sulphonylurea, glimepiride, and its metabolites. The assay involves extraction with diethyl ether, thermolysis of the sulphonylureas at 100 degrees C and trapping of the resulting amines with 2,4-dinitrofluorobenzene. The derivatives were quantitated on a reversed-phase column by absorbance at 350 nm using a step gradient for the three compounds in serum and an isocratic run for the metabolites in urine. Analogous compounds were used as internal standards. The detection limit was 5 ng/ml for glimepiride and metabolite II and 10 ng/ml for metabolite I using 1 ml of serum. The method has been applied to the analysis of serum and urine samples from pharmacokinetic studies in humans.

A rapid high-performance liquid chromatography assay of glibenclamide in serum

A rapid high-performance liquid chromatography (HPLC) determination of glibenclamide in human serum is described. Serum samples to which flufenamic acid has been added as internal standard were treated with acetonitrile as a protein precipitant. After centrifugation, separation and reconstitution, the redissolved residue was eluted from 5 mu Spherisorb C-8 reversed phase column at ambient temperature using a mobile phase consisting of acetonitrile-water (45:55 v/v) at pH 3.7-3.8 and pumped at a flow rate 2 ml/min. The effluent was monitored at 230 nm. The analysis time was no longer than 12 min. A linear relationship between the peak height ratio (glibenclamide/flufenamic acid) and concentration was obtained in the range 20-400 ng/ml. A typical calibration curve has a regression equation y = 0.0035x + 0.015 (r = 0.9999). The detection limit of glibenclamide in serum was 20 ng/ml. The mean recovery of drug from serum samples spiked with known amounts of glibenclamide was 96.77%. Within-day and between-day coefficients of variation were 1.6-4.0% and 1.4-3.5%, respectively. Stability testing indicated that glibenclamide was stable for at least 10 days in serum -20 degrees C. The method developed was applied to determine some pharmacokinetic parameters after the oral administration of 5 mg glibenclamide tablets to a human volunteer.

High-performance liquid chromatographic determination of glibenclamide in human plasma and urine

A selective and sensitive high-performance liquid chromatographic method for determination of intact glibenclamide in human plasma or urine has been developed. With glibornuride as internal standard, acid-buffered plasma or urine was extracted with benzene. The organic layer was evaporated and the residue was dissolved in equilibrated mobile phase (acetonitrile-phosphate buffer 0.01 M pH 3.5, 50:50). An aliquot of 20 microliters was chromatographed on a Spherisorb ODS reversed-phase column, and quantitation was achieved by monitoring the ultraviolet absorbance at 225 nm. The response was linear (0-1000 ng/ml) and the detection limit was 5-10 ng/ml in plasma or urine. The within-assay variation was less than or equal to 10%. No interferences from metabolites or endogenous constituents could be noted. The utility of the method was demonstrated by analysing glibenclamide in samples from diabetic subjects on therapeutic doses of the drug.

Pharmacokinetics of glyburide

The pharmacokinetics of glyburide can be described by a two-compartment open model. Terminal-phase descriptions are formulation-dependent and are complicated by apparent food-associated mobilization of drug from the stomach. Some researchers indicate a possible third (or deep) compartment, but this appears to be an artifact of a nonspecific drug assay. Although no accumulation has been observed in short-term studies, further investigation of the possibility of drug accumulation with long-term therapy is needed. Distribution of glyburide is affected by high affinity for serum albumin (99 percent bound), and elimination of the drug appears to be evenly divided between biliary and renal routes. The biologic half-life of glyburide is not significantly correlated with renal function in subjects with creatinine clearances of 30 ml/minute/1.7 m2 or more. Gradations in disease state, multiple sites of sulfonylurea action, and inter-patient variability have made it difficult to relate biologic response to glyburide serum levels.

Drug level monitoring: chromatography of some minor groups of drugs

Some important facts about the chromatographic separation of a number of selected categories of drugs are summarized. The data refer to the chromatographic method of choice, stationary phase, mobile phase (carrier gas), detection procedure and (where available) method sensitivity. Also, fundamental instrumental parameters, namely injector, column and detector temperature, carrier gas and mobile phase flow-rate and gradient set-up are reported here. In all cases also the source material used for analysis is specified. The data are presented in table form, each table dealing with a particular category of drugs. The following categories of drugs are being dealt with: anthelmintics, antiarteriosclerotics, antibacterials, anticholinergics and cholinergics, anticoagulants, antidiabetics, antiemetics, antimycotics, antihistamines, antimalarials, antiparasitics, antiparkinsonics, antitussives, antiulcer drugs, antiviral compounds, appetite depressants and immunosuppressives.

The identification, assay and purity determination of chlorpropamide, glibenclamide and tolbutamide and their tablet preparations by thin-layer chromatography

A thin-layer chromatographic procedure is described for the identification and quantitative determination of chlorpropamide, glibenclamide and tolbutamide in both powder and tablet form. The coefficient of variation of the method is 0.6-0.7%, and results show good agreement with those obtained by the B.P. methods of assay. The TLC procedure has the advantage of greater specificity, and can also be used to identify and limit degradation products that may be present.

High-performance liquid column and thin-layer chromatographic determination of human serum glibenclamide at therapeutic levels

For glibenclamide bioavailability studies in serum, high-performance liquid column and thin-layer chromatographic methods were introduced. Both methods are specific, accurate and sensitive with detection limits of at least 5 ng of glibenclamide per ml of serum. Detection is performed in the ultraviolet at wavelengths of 200 nm for liquid chromatography or 300 nm for thin-layer chromatography. Serum levels determined by either method correlated well with those determined by an already existing radioimmunoassay. Some pharmacokinetic data were computed using a one-compartment open model.