Simultaneous determination of oral antidiabetic drugs in human plasma using microextraction by packed sorbent and high-performance liquid chromatography.

In this study, a simple method using microextraction by packed sorbent and high-performance liquid chromatography with ultraviolet detection for simultaneous determination of chlorpropamide, gliclazide and glimepiride in human plasma was developed and validated. A fractional factorial design and a complete factorial design were applied to evaluate the parameters which could affect the extraction and desorption steps, respectively. All parameters in the extraction step (pH, sample volume, sample dilution and number of aspiration/ejection cycles) and in the desorption step (percentage of acetonitrile in the elution solvent and number of aspirations of elution solvent through the device) were statistically significant (p>0.05) when recovery was used as response. The developed method allowed the use of small volumes of sample and solvents and rapid separation by using a fused core column (only 2.2min were needed). This method was fully validated showing selectivity, precision, accuracy and linearity over the range 1.0-50.0µgmL(-1) for chlorpropamide, 1.0-10.0µgmL(-1) for gliclazide and 0.1-1.0µgmL(-1) for glimepiride. Finally, the validated method was applied in the analysis of samples from volunteers containing the three tested analytes.

The influence of lamivudine, stavudine and nevirapine on the pharmacokinetics of chlorpropamide in human subjects.

Diabetic patients tend to be prone to infections, and multiple drug therapy cannot be ruled out in the management of diabetes. The effect of three routinely prescribed antiretroviral (ARV) drugs on the pharmacokinetic profile of an antidiabetic drug, chlorpropamide, was investigated in 18 human subjects, who had recently been diagnosed positive for human immunodeficiency virus (HIV) infection. The volunteers, aged 22-44 years and weighing 59-66 kg, were randomized into three groups with six subjects in each group. The study was carried out in two phases; in the first phase, all the subjects received chlorpropamide (250 mg) in a fasting state. In the second phase, the subjects received 250 mg of chlorpropamide together with lamivudine (150 mg) or stavudine (40 mg) or nevirapine (200 mg) in a fasting state. Chlorpropamide concentrations in the plasma were determined using a high performance liquid chromatography (HPLC) method developed earlier in our laboratory, while plasma glucose levels were determined using the standard glucose oxidase method. Lamivudine and stavudine decreased significantly (P < 0.05) the mean maximum plasma concentrations (Cmax) and the area under the plasma concentration-time curve (AUC(0-168h)) of chlorpropamide, while both drugs significantly increased the absorption half-life (t(1/2ab)) and elimination half-life (t(1/2el). the apparent volume of distribution (Vd) and the plasma clearance rate (Cl) of chlorpropamide (P < 0.05). The plasma glucose levels were also significantly increased between 0.5 - 4 h post dose (P < 0.05). However, it was found that the pharmacokinetic parameters of chlorpropamide and the blood glucose levels were not significantly altered by the co-administration with nevirapine.

Effect of Nigerian meals on the pharmacokinetics of chlorpropamide in type II diabetic patients.

Food-drug interactions are best evaluated on an individual drug basis, in a group of subjects in a population at risk. This is due to their complex nature, which is a function of type and size of meal, the physical and chemical form of the drug and the time lapse between food intake and drug administration. This work was aimed at investigating the effect of three different Nigerian meals, which are regularly consumed by the three major tribes in Nigeria, on the pharmacokinetics of chlorpropamide, a drug commonly used to treat Type II diabetes in this country. Meal A (maize flour meal) was composed of 81% carbohydrate, 3% protein and 11% fat; meal B (cassava flour meal) was composed of 76% carbohydrate, 3% protein and 15% fat; while meal C (browned yam flour meal) was composed of 85% carbohydrate, 2% protein and 8% fat. The effects of the three meals were investigated by administering each of the meals alone, without the medicinal drug (Treatment I); in Treatment II each meal was administered 30 min following the administration of 250 mg chlorpropamide; in Treatment III the drug was administered together with each of the standard meals. Analysis of the plasma levels of chlorpropamide was performed by high performance liquid chromatography (HPLC). Ingestion of the meal alone (Treatment I) resulted in a significant difference in postprandial plasma glucose levels. The time to maximum plasma chlorpropamide concentration was significantly increased in Treatment III (P < 0.05), while all pharmacokinetic parameters and plasma glucose levels were not significantly altered in Treatment II. Analysis of the results demonstrated a better glycaemic response with meals A and C compared with meal B.

Comparative bioavailability study with two chlorpropamide tablet formulations in healthy volunteers.

OBJECTIVE: The aim of this study was the assessment of the bioequivalence of two formulations (250 mg tablet) of chlorpropamide (CAS 94-20-2) in 36 healthy volunteers of both sexes. METHODS: The study was conducted using an open, randomized, two-period crossover design with a 3-week washout interval. Plasma samples were obtained over a 72-h period. Plasma chlorpropamide concentrations were analyzed by liquid chromatography coupled to tandem mass spectrometry (LC-MS-MS) with positive ion electrospray ionization using multiple reaction monitoring (MRM). From the chlorpropamide plasma concentration vs time curves, the following pharmacokinetic parameters were obtained: AUC(0-72h), AUC(inf) and C(max). RESULTS: The limit of quantification was 0.1 microg/mL for plasma chlorpropamide analysis. The geometric mean and respective 90 % confidence interval (CI) of Test/ Reference percent ratios were 93.99% (87.11%-101.41%) for C(max), 92.45% (85.96%-99.44%) for AUC(0-72h) and 90.30% (83.35%-97.82%) for AUC(0-inf). CONCLUSION: Since the 90 % CI for AUC(0-72h), AUC(0-inf) and C(max) ratios were within the 80-125%interval proposed by the US FDA, it was concluded that chlorpropamide 250 mg tablet (test formulation) was bioequivalent to the reference 250 mg tablet for of both the rate and extent of absorption.

Identification of sulfonylureas in serum by electrospray mass spectrometry.

Identification of sulfonylureas in serum is important in the diagnosis of hypoglycemic crisis of unknown origin. Methods based on HPLC with UV or fluorescence detection may give false positive results. Mass spectrometry may successfully avoid this problem. The described method allows the simultaneous identification and quantification of tolbutamide, chlorpropamide, glibenclamide, and glipizide in human serum using one of the tested sulfonylureas as the internal standard. Serum purification is carried out by solid-phase extraction with ENVI-C18 cartridges and samples are analyzed by liquid chromatography-electrospray mass spectrometry. For all drugs, the limit of detection and the limit of quantification are about 2 and 10 ng/ml, respectively.

Screening of chlorpropamide in horse plasma by high-performance liquid chromatography with ultraviolet absorbance detection, and confirmation by gas chromatography-mass spectrometry.

A chromatographic method was developed to detect and confirm the presence of chlorpropamide (I) in horse plasma samples, for antidoping control. The plasma sample (1 ml) was extracted with dichloromethane and screened by high-performance liquid chromatography, and confirmation of the drug's presence was accomplished by using gas chromatography-mass spectrometry (GC-MS). The limit of detection was found to be 3.5 ng/ml at a signal-to-noise ratio of three. Derivatization of I with N,O-bis-(trimethylsilyl)trifluoroacetamide with 1% trimethylchlorosilane allowed for highly stable, accurate and sensitive GC-MS analysis. Plasma samples collected after the administration of diabinese were positive for I (one-five days) in all samples analysed.

The effect of serum Ca2+ compensation on the efficacy of chlorpropamide in alloxan-diabetic rabbits.

A decrease in serum Ca2+ concentration was observed in alloxan-diabetic rabbits, with recovery of serum Ca2+ levels achieved following insulin therapy. This suggested that the diabetic condition directly relates to the decrease in serum Ca2+ levels. The efficacy of chlorpropamide in alloxan-diabetic rabbits after intravenous injection (150 mumol kg-1) was less than that in normal rabbits as measured by the serum insulin levels, and the efficacy did not change when the dose was increased. However, compensation of serum Ca2+ levels in alloxan-diabetic rabbits caused an increase in the efficacy of chlorpropamide observed as an increase in serum insulin and a decrease in serum glucose levels.

A screening test for detecting sulfonylureas in plasma.

Hypoglycemia induced by surreptitious sulfonylurea ingestion can be difficult to distinguish from an insulin-secreting tumor. We describe a technique for detecting most of the common sulfonylurea drugs in plasma. After preliminary acidification, and extraction in ether, the residue is reconstituted and injected onto a Versapack high-performance liquid chromatography column. Detection is at 230 nm. This procedure gives good separation of chlorpropamide, glibenclamide, gliclazide, glipizide, and tolbutamide. Results are semiquantitative but the sensitivity of the assay is sufficient to detect and identify clinically active concentrations of all five drugs. It is a rapid and reliable screening test. Four representative case histories are reported in which the screen proved to be of diagnostic value.

Comparative bioavailability of two brands of chlorpropamide in Kenyans.

The relative bioavailability of two brands of chlorpropamide, Dibonis, and Diabinese has been evaluated in four healthy male volunteers in a randomized, balanced, cross-over study. No statistically significant differences were observed in the absorption rate constant, ka, time to reach peak serum concentration, tp, maximum serum concentration, Cmax, the overall elimination rate constant, kel, and the area under the curve, AUC, at 95% confidence level.

Chlorpropamide overdose in renal failure: management with charcoal hemoperfusion.

A potentially lethal chlorpropamide overdose in a patient with chronic renal failure on long-term hemodialysis was treated by two courses of charcoal hemoperfusion. Hemoperfusion shortened the half-life clearance of the drug from a mean value of 93.6 to 3.4 hours. Calculation of the fractional extraction indicated that hemoperfusion reduced the body burden of the drug by 24% and 19% (mean values) during the first and second hours of treatment, respectively. We conclude that charcoal hemoperfusion should be considered a definitive therapeutic option in such cases.

Chlorpropamide alcohol flushing: a normal response?

The relationship between chlorpropamide alcohol flushing and non-insulin dependent diabetes remains uncertain. It is known, however, that the frequency of facial flushing with alcohol and the temperature response depend upon both the plasma level of chlorpropamide and the starting facial temperature [10]. We tested 23 young adult non-diabetic subjects with 8 g of ethanol after a dose of chlorpropamide 250 mg twice daily for 2 days or a placebo, in a double blind, cross-over manner. Previously, nine other subjects had participated in a pilot study to assess the safety of the chlorpropamide dose and to ensure that adequate plasma chlorpropamide levels were achieved. No subject was negative for chlorpropamide alcohol flushing, as defined by the following criteria: facial temperature rise of 35% or more of maximum possible rise, observer assessment or subject assessment. In 26 of the total 32 subjects, all three criteria were fulfilled. Thus, among young, healthy non-diabetic adults chlorpropamide alcohol flushing would appear to be a normal phenomenon.

Erythrocyte aldehyde dehydrogenase, plasma chlorpropamide concentrations and the chlorpropamide alcohol flush.

Erythrocyte aldehyde dehydrogenase activity (EALDH) was measured in 21 diabetics on long-term chlorpropamide therapy. Median EALDH was 0.362 units, range 0.108 to 0.750 units and correlated neither with previously assessed chlorpropamide alcohol flushing nor with coincident plasma or erythrocyte chlorpropamide concentration. The hypothesis that genetic or permanently acquired reduction in EALDH correlates with CPAF status was not supported. There was no concentration-related inhibition of the enzyme by prevailing plasma or erythrocyte chlorpropamide.

Enhancement by sodium salicylate of the blood glucose lowering effect of chlorpropamide-drug interaction or summation of similar effects?

The ability of sodium salicylate (3 g) to enhance the blood glucose lowering action of chlorpropamide (200 mg) has been confirmed in healthy male volunteers who received an oral test dose of 50 g glucose. Salicylate raised the plasma concentration of insulin and lowered that of cortisol but did not alter the concentration of chlorpropamide. The area under the blood glucose concentration-time curve was used as the measure of drug response and the significance of drug effects was assessed by analysis of variance. In one study on five volunteers the effect of combining salicylate and chlorpropamide was additive. In a second study on six volunteers 200 mg chlorpropamide, 3 g sodium salicylate and 100 mg chlorpropamide + 1.5 g salicylate were equi-effective. The enhancement of chlorpropamide action by salicylate in this single dose study is consistent with the summation of similar effects. It is not necessary to postulate an interaction.

Aldehyde dehydrogenase activity and large vessel disease in diabetes mellitus. A preliminary study.

Type II diabetic subjects, 26 with symptoms and/or signs of large vessel disease (LVD group) and 26 free from clinical vascular disease (FVD group), matched for sex, age, body weight, and duration of diabetes after diagnosis, together with 28 healthy controls participated in a preliminary study on new potential risk factors of large vessel disease. The activity of erythrocyte aldehyde dehydrogenase (ALDH) was significantly higher (P less than 0.005) in the LVD than in the FVD group and in the controls, as indicated by a shorter half-life of acetaldehyde in homogenates of erythrocytes and plasma (100 +/- 11, 203 +/- 28, and 180 +/- 21 min, respectively). The results were unaffected by antidiabetes therapy, blood glucose control, alcohol consumption, or by recognized risk factors of angiopathy, such as blood pressure, hyperlipidemia, or smoking. Whether ALDH activity is a primary factor in large vessel disease or is merely a secondary phenomenon is unknown. However, ALDH activity is a critical factor determining chlorpropamide alcohol flush (CPAF), which has been suggested to be an inherited trait in some type II diabetic subjects. In conclusion, high ALDH activity was shown to be associated with an increased risk of large vessel disease in diabetes.

Prevalence of chlorpropamide alcohol flush in Jewish Israeli diabetics. The role of serum chlorpropamide concentrations.

Among 53 patients with noninsulin-dependent diabetes (NIDD), chlorpropamide alcohol flushing (CPAF) was more prevalent than among 18 patients with insulin-dependent diabetes (64 vs. 28%, respectively). Among the former, chronic users of chlorpropamide (CP) had a higher prevalence of CPAF than those challenged once with the drug (86 vs. 56%, respectively). Serum CP concentrations were much higher in CP-treated patients, but levels were not different in CPAF-positive compared with CPAF-negative subjects, regardless of the length of their exposure to the drug. Our data confirm the association between CPAF and NIDD in a Jewish Israeli diabetic population and the effect of serum CP levels on the prevalence of this phenomenon.

On plasma chlorpropamide, body weight and sex difference in chlorpropamide alcohol flush (CPAF).

There is evidence that the plasma chlorpropamide (CP) concentration is an important determinant of the chlorpropamide alcohol flush (CPAF). In 74 type 2 diabetics a highly significant correlation (r = 0.51, p less than 0.001) was present between the levels of plasma CP and the appearance of CPAF, measured as an index (the sum of the increase of the skin temperature and one-fourth of plasma acetaldehyde increase). Lower or no correlations were found when different threshold levels were considered. Body weight was significantly (p less than 0.001) inversely correlated to plasma chlorpropamide levels, which resulted in higher CP levels in females (mean body weight 68.6 kg, CP concentration 34.4 mg/l) than in males (83.4 kg, 26.0 mg/l), which explains the female preponderance among flushers.