HPLC Determination of Fexofenadine in Human Plasma For Therapeutic Drug Monitoring and Pharmacokinetic Studies.

A simple and sensitive method was developed for fexofenadine determination in human plasma by liquid chromatography with ultraviolet detection. Satisfactory separation was achieved on a Hypersil® BDS C18 column (250 × 4.6 mm, 5µm) using a mobile phase comprising 20 mm sodium dihydrogen phosphate-2 hydrate (pH adjusted to 3 with phosphoric acid)-acetonitrile at a ratio of 52:48, v/v. The elution was isocratic at ambient temperature with a flow rate of 1.0 mL/min. The UV detector was set at 215 nm for the drug and 330 nm for the internal standared (tinidazole). The total time for a chromatographic separation was ~6.5 min. Linearity was demonstrated over the concentration range 0.01-4 µg/mL. The observed within- and between-day assay precision ranged from 0.346 to 13.6%; accuracy varied between 100.4 and 111.2%. This method was successfully applied for therapeutic drug monitoring in patients treated with clinical doses of fexofenadine and for pharmacokinetic studies. Copyright © 2015 John Wiley & Sons, Ltd.

Simultaneous determination of paracetamol and methocarbamol in human plasma By HPLC using UV detection with time programming: application to pharmacokinetic study.

BACKGROUND: A combination of methocarbamol (MET) and paracetamol (PAR) is a widely used treatment approach. It provides complementary modes of action for treatment of pain associated with muscle spasm. The aim of this work was to develop and validate a new sensitive and reproducible isocratic reversed phase HPLC-UV detection method for simultaneous determination of MET and PAR in human plasma for the routine use in a therapeutic drug monitoring and pharmacokinetic laboratories. METHODS: A simple HPLC assay was developed and validated for the simultaneous determination of the above-mentioned drugs in small samples of human plasma (0.25 mL). After protein precipitation with methanol, satisfactory separation was achieved on a Hypersil® BDS C18 column (250 mm × 4.6 mm, 5 µm) using a mobile phase comprising 20 mM sodium dihydrogen phosphate buffer (pH=3) and methanol at a ratio of 80:20, v/v; the elution was isocratic at ambient temperature with a flow rate of 1.2 ml/min. The UV detector was programmed at 254 nm for 7.0 min to measure PAR and IS and at 272 nm for the subsequent 3 min to measure MET. RESULTS: Linearity was demonstrated over the concentration range from 0.02 to 20 µg/ml (mean R(2) = 0.9998, n = 10). The observed within- and between-day assay precision ranged from 1.11 to 9.4 and 2.46 to 10.0% for PAR and MET, respectively; whereas, accuracy varied between 95.2-101% and 93.9-102.2% for PAR and MET, respectively. Mean drug recovery was 99.8 for PAR and 99.0% for MET. PAR and MET were stable in frozen plasma over a period of 3 months at -80 °C. CONCLUSIONS: The validated method was applied successfully to a bioequivalence study of PAR/MET (500/400 mg) fixed dose combination tablet in healthy volunteers (n=24).

Effect of the formulation on the bioequivalence of meloxicam: tablet and suspension.

Meloxicam is a non-steroidal anti-inflammatory drug of the enolic acid class that preferentially inhibits cyclooxygenase-2 imparting analgesic, antipyretic and anti-inflammatory effects. This study was conducted to evaluate the effect of formulation on the pharmacokinetics (PK) and comparative bioavailability of suspension (reference) and tablet (test) formulations of meloxicam. In this in vivo study was established according to a single-center, randomized, single-dose, laboratory-blinded, 2 way, cross-over study with a washout period of 2 weeks. Under fasting conditions, 24 healthy Egyptian male volunteers were randomly allocated to receive a single oral dose of 15 mg meloxicam either as 10 mL of a marketed suspension or one tablet. Plasma samples were obtained over a 96-h interval and analyzed for meloxicam by reversed phase liquid chromatography with ultraviolet detection. A non-compartmental model was used to determine the PK parameters of meloxicam. The 90% confidence intervals for the ratio of log transformed values of Cmax, AUC0-t, and AUCt-∞ of the 2 treatments were within the acceptable range (0.8-1.25) for bioequivalence. From PK perspectives, in this small study in healthy Egyptian adult male volunteers, a single 15 mg dose of the tablet formulation was bioequivalent to a single 15 mg dose of the suspension formulation with no significant effect of formulation based on the US FDA's regulatory definition. No adverse events occurred or were reported during the study and both formulations were well tolerated.

Comparative in vitro dissolution and in vivo bioavailability of diflunisal/naproxen fixed-dose combination tablets and concomitant administration of diflunisal and naproxen in healthy adult subjects.

A simple validated high-performance liquid chromatography (HPLC) assay was developed for determination of diflunisal and naproxen in human plasma samples. This is to compare the bioavailability of diflunisal-naproxen fixed-dose combination (FDC) with their separate dosage forms. The in vitro dissolution study was adopted to compare the dissolution behavior of FDC with respect to separate marketed tablets. In vivo study was conducted according to a single-center, randomized, single-dose, laboratory-blinded, 2 Way, Cross-Over Study with a washout period of 10 days. Under fasting conditions, 24 healthy Egyptian male volunteers were randomly allocated to receive a single oral dose of either one FDC tablet or co-administration of two separate diflunisal and naproxen marketed tablets. Plasma samples were obtained over a 72-h interval and analyzed for diflunisal and naproxen by reversed phase liquid chromatography with UV detection. The pharmacokinetic parameters Cmax, AUC0-t, AUC0-∞, tmax, and t1/2 were determined from plasma concentration-time profiles. The 90% confidence intervals for the ratio of log transformed values of Cmax, AUC0-t, and AUCt-∞ of the 2 treatments were within the acceptable range (0.8-1.25) for bioequivalence. From pharmacokinetic and in vitro studies perspectives, 1 FDC tablet demonstrated similar relative bioavailability with the 2 individual -reference tablets.