Rapid and simple method for the analysis of nateglinide in human plasma using HPLC analysis with UV detection

Hydrophilic interaction liquid chromatography-electrospray ionization mass spectrometry combined with fabric phase sorptive extraction for therapeutic drug monitoring of pioglitazone, repaglinide, and nateglinide in human plasma

Polypharmacy in type 2 diabetes is an issue of major concern as the prescription of multiple medi-cations for the management of diabetes-associated comorbidities can lead to drug-to-drug interactions, which can pose serious risks to patients' health. Within this context, the development of bioanalytical methods for monitoring the therapeutic levels of antidiabetic drugs is notably useful to ensure patients' safety. In the present work, a liquid chromatography-mass spectrometry method for the quantitation of pioglitazone, repaglinide, and nateglinide in human plasma is described. Sample preparation was performed by fabric phase sorptive extraction (FPSE), and hydrophilic interaction liquid chromatography (HILIC) was implemented for the chromatographic separation of the analytes, using a ZIC®-cHILIC analytical column (150 × 2.1 mm, 3 µm) under isocratic elution. The mobile phase consisted of 10 mM ammonium formate aqueous solution (pH = 6.5)/ acetonitrile, 10/90 v/v, and was pumped at a flow rate of 0.2 mL min^-1. Design of Experiments was used during the development of the sample preparation method to gain deeper insight into the effect of various experimental parameters on extraction efficiency, their potential interactions and to optimize the recovery rates of the analytes. The linearity of the assay was assessed over the ranges of 25 to 2000, 6.25 to 500, and 125 to 10000 ng mL^-1 for pioglitazone, repaglinide, and nateglinide, respectively. The presented method was fully validated and can be used for the therapeutic monitoring of the targeted analytes in human plasma samples.

Carbamazepine

This chapter includes the aspects of carbamazepine. The drug is synthesized by the use of 5H-dibenz[b,f]azepine and phosgene followed by subsequent reaction with ammonia. Carbamazepine is generally used for the treatment of seizure disorders and neuropathic pain, it is also important as off-label for a second-line treatment for bipolar disorder and in combination with an antipsychotic in some cases of schizophrenia when treatment with a conventional antipsychotic alone has failed. Other uses may include attention deficit hyperactivity disorder, schizophrenia, phantom limb syndrome, complex regional pain syndrome, borderline personality disorder, and posttraumatic stress disorder. The chapter discusses the drug metabolism and pharmacokinetics and presents various methods of analysis of this drug such electrochemical analysis, spectroscopic analysis, and chromatographic techniques of separation. It also discusses its physical properties such as solubility characteristics, X-ray powder diffraction pattern, and thermal methods of analysis. The chapter is concluded with a discussion on its biological properties such as activity, toxicity, and safety.

Stability-indicating HPTLC method for simultaneous determination of nateglinide and metformin hydrochloride in pharmaceutical dosage form

A stability indicating high performance thin layer chromatography (HPTLC) method was developed and validated for determination of two anti-diabetic drugs, nateglinide and metformin hydrochloride in co-formulations. Study was performed on pre-coated silica gel HPTLC plates using chloroform:ethyl acetate:acetic acid (4:6:0.1 v/v/v) as the mobile phase. A TLC scanner set at 216 nm was used for direct evaluation of the chromatograms in the reflectance/absorbance mode. Method was validated according to ICH guidelines. The correlation coefficients of calibration curves were found to be 0.996 and 0.995 in the concentration range of 200-2400 and 500-3000 ng band(-1) for nateglinide and metformin, respectively. The method had an accuracy of 99.72% for nateglinide and 100.08% for metformin hydrochloride. The method had the potential to determine these drugs simultaneously from dosage forms without any interference of the tablets excipients. Nateglinide and metformin hydrochloride were also subjected to acid, base, oxidation, wet, heat and photo-degradation studies. The degradation products obtained were well resolved from the pure drugs with significantly different Rf values. As the method could effectively separate the drugs from its degradation products, it can be used for stability-indicating analysis.

Determination of the L-enantiomer of nateglinide in pharmaceutical formulations by micellar electrokinetic chromatography

An analytical micellar electrokinetic chromatographic method was developed and validated for the determination of the L-enantiomer of nateglinide. Separations were carried out in a 50 μm, 64.5/56 fused-silica capillary. The optimized conditions included 75 mM borate buffer, pH 9.2, containing 50 mM of sodium dodecyl sulfate and 25 mg/mL of methyl-β-cyclodextrin as background electrolyte, an applied voltage of 20 kV and a temperature of 15, UV detector at 210 nm. The assay was validated for the L-enantiomer of nateglinide. The limit of detection and quantification were 0.07 and 0.2% respectively. Intraday precision was ranged between 0.12 and 1.7%. Interday precision ranged between 0.73 and 1.73%. The assay was applied to the determination of the L-enantiomer of nateglinide in pharmaceutical formulations.

A Validated Stability Indicating LC Method for Nateglinide

A simple, isocratic, rapid and accurate reverse phase high-performance liquid chromatography (RP-HPLC) method was developed for the quantitative determination of Nateglinide. The developed method is also applicable for determination of related substance in bulk drugs. The chromatographic separation was achieved on a Hypersil C18 (250x4.6 mm 5 microm) column using aqueous mixture of 0.025 M potassium hydrogen phosphate and 0.1% triethyl amine, v/v (pH 3.0 with dilute phosphoric acid)-methanol (25:75, v/v) as a mobile phase. Solution concentrations were measured on a weight basis to avoid the use of an internal standard. The chromatographic resolutions between Nateglinide and its potential impurities A and B were found to be greater than four. Forced degradation studies were performed for Nateglinide using acid (0.5 N hydrochloric acid), base (0.5 N sodium hydroxide), oxidation (3% hydrogen peroxide) heat (60 degrees C) and UV light (254 nm). The limit of detection and limit of quantification of Nateglinide, impurities A and B were found to be 0.05 and 0.15 microg /mL, respectively for 20 microL injection volume. The percentage recovery of Nateglinide was ranged from 98.4 to 100.9. The percentage recovery of impurities in Nateglinide sample was ranged from 96.8 to 103.5. The developed RP-HPLC method was validated with respect to linearity, accuracy, precision, robustness, and forced degradation studies prove the stability indicating power of the method.

Determination of nateglinide in human plasma by high-performance liquid chromatography with pre-column derivatization using a coumarin-type fluorescent reagent

A sensitive and selective high-performance liquid chromatographic method has been developed and validated for the determination of nateglinide in human plasma. Nateglinide and the internal standard, undecylenic acid, were extracted from plasma by liquid-liquid extraction using a mixture of ethyl acetate-diethyl ether, 50:50 (v/v). Pre-column derivatization reaction was performed using a coumarin-type fluorescent reagent, N-(7-methoxy-4-methyl-2-oxo-2H-6-chromenyl)-2-bromoacetamide. The derivatization proceeded in acetone in the presence of potassium carbonate and catalyzed by 18-crown-6 ether. The fluorescent derivatives were separated under isocratic conditions on a Hypersil BDS-C8 analytical column (250.0 mm x 2.1 mm i.d., particle size 5 microm) with a mobile phase that consisted of 65% acetonitrile in water and pumped at a flow rate of 0.50 mL min(-1). The excitation and emission wavelengths were set at 345 and 435 nm, respectively. The assay was linear over a concentration range of 0.05-16.00 microg mL(-1) for nateglinide with a limit of quantitation of 0.05 microg mL(-1). Quality control samples (0.05, 4.50 and 16.00 microg mL(-1)) in five replicates from five different runs of analysis demonstrated intra-assay precision (%coefficient of variation <6.8%), inter-assay precision (%coefficient of variation <1.6%) and an overall accuracy (%relative error) less than -3.4%. The method can be used to quantify nateglinide in human plasma covering a variety of pharmacokinetic or bioequivalence studies.

Nateglinide quantification in rabbit plasma by HPLC: Optimization and application to pharmacokinetic study

A rapid, simple, and sensitive HPLC method with UV detection was developed and validated for the determination of nateglinide (NTG) from rabbit plasma. The retention behavior of NTG and gliclazide (GLZ, internal standard-IS) as a function of mobile phase pH, composition and flow rate was investigated. Separation was developed on a reverse-phase C(18) column (250 mm x 4.6mm i.d., 5 microm particle size), using a mixture of acetonitrile (ACN):10mM phosphate buffer (PBS, pH 3.0) in the ratio of 70:30(%v/v) at a flow rate of 1.0 ml/min with UV detection at 203 nm within 8 min, and quantified based on drug/IS peak area ratios. The plasma samples were prepared by a simple deproteinization with a mixture of methanol and acetonitrile, yielding more than 97.86% extraction efficiencies. The calibration curve was linear (correlation coefficient of 0.9984) in the concentration range of 10-2500 ng/ml. The limit of detection (LoD) and limit of quantitation (LoQ) were found to be 2.91 and 9.70 ng/ml, respectively. Both the intra-day and inter-day precisions at four tested concentrations were below 1.32% R.S.D. The present method was selective enough to analyze NTG in rabbit plasma without any tedious sample clean-up procedure and was successfully applied for estimating the pharmacokinetic parameters of NTG following oral administration of a single 15 mg NTG to white albino rabbits.

Determination of nateglinide in animal plasma by micellar electrokinetic chromatography and on-line sweeping technique

A micellar electrokinetic chromatography (MEKC) method was developed for the determination of nateglinide in animal plasma by on-line sweeping technique, in which plasma samples were simply deproteinized with acetonitrile, and analyzed with 16 mmol/L NaH2PO4 + 6 mmol/L Na2B4O7 + 60 mmol/L sodium dodecyl sulfate (SDS) (pH 7.14) as the running buffer, a fused-silica capillary as the separation tube, 21 kV as the running voltage and UV detection at 214 nm. Under these conditions, more than 100-fold enrichment of nateglinide was obtained with the good linear relation in the range of nateglinide plasma concentration 0.2-7 mg/L (R = 0.998). The method could be applied successfully to determine trace drugs in clinical analysis.

Influence of CYP2C9 and CYP2D6 Polymorphisms on the Pharmacokinetics of Nateglinide in Genotyped Healthy Volunteers

BACKGROUND

The oral hypoglycaemic drug nateglinide is eliminated from the human body via hepatic biotransformation and renal tubular secretion. According to in vitro data, about 70% of nateglinide intrinsic clearance may be mediated by cytochrome P450 (CYP) 2C9 and a smaller fraction by CYP3A4 and CYP2D6.

OBJECTIVE

To assess the impact of CYP2C9 polymorphisms and of the CYP2D6 poor metaboliser genotype on the pharmacokinetics of nateglinide and its effects on insulin, glucose and glucagon in plasma.

DESIGN AND PARTICIPANTS

A prospective clinical study in 26 healthy volunteers chosen for their CYP2C9 and CYP2D6 genotype was conducted with individuals carrying wild-type genotype as reference group.

METHODS

Serial plasma nateglinide, glucose, insulin and glucagon concentrations were measured over 34 hours after a 180 mg dose of nateglinide under challenge with 75 g of oral glucose at 0, 4 and 8 hours after nateglinide intake. Kinetics were evaluated by nonparametric methods and by population pharmacokinetic-pharmacodynamic modelling.

RESULTS

Significantly reduced oral nateglinide clearance was found in carriers of CYP2C9*3 alleles, (p < 0.01), whereas carriers of CYP2C9*2 alleles had kinetic parameters similar to those of carriers of the wild-type allele (p = nonsignificant). Median total clearances were 7.9, 8.4, 6.5, 6.9, 5.8 and 4.1 L/h in carriers of the CYP2C9 genotypes *1/*1, *1/*2, *2/*2, *1/*3, *2/*3 and *3/*3. Median clearance in three carriers of two deficient CYP2D6 alleles was 9.4 L/h. These differences in nateglinide kinetics due to CYP2C9 genotypes did not result in statistically significant differences in plasma glucose, insulin and glucagon. Pharmacokinetic-pharmacodynamic modelling revealed a minor effect of CYP2C9 genotype on insulin and glucose, and extrapolations indicated that carriers of the CYP2C9*3/*3 genotype may be at a slightly higher risk of hypoglycaemia compared with carriers of CYP2C9*1, particularly when taking nateglinide doses above 120 mg.

CONCLUSION

The effect of CYP2C9 polymorphisms on nateglinide kinetics may cause a slightly increased risk for hypoglycaemia, which may become relevant in diabetic patients.