Core shell stationary phase for a novel separation of some COVID-19 used drugs by UPLC-MS/MS Method: Study of grapefruit consumption impact on their pharmacokinetics in rats

A sensitive and selective UPLC-MS/MS method was developed for the synchronized determination of four drugs used in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), namely, azithromycin, apixaban, dexamethasone, and favipiravir in rat plasma. using a Poroshell 120 EC-C18 column (50 mm × 4.6 mm, 2.7 m) with a high-resolution ESI tandem mass spectrometer detection with multiple reaction monitoring. We used an Agilent Poroshell column, which is characterized by a stationary phase based on non-porous core particles. With a remarkable improvement in the number of theoretical plates and low column backpressure. In addition, the developed method was employed in studying the potential food-drug interaction of grapefruit juice (GFJ) with the selected drugs which affects their pharmacokinetics in rats. The LC-MS/MS operated in positive and negative ionization mode using two internal standards: moxifloxacin and chlorthalidone, respectively. Liquid- liquid extraction of the cited drugs from rat plasma was accomplished using diethyl ether: dichloromethane (70:30, v/v). The analytes were separated using methanol: 0.1 % formic acid in water (95: 5, v/v) as a mobile phase in isocratic mode of elution pumped at a flow rate of 0.3 mL/min. A detailed validation of the bio-analytical method was performed in accordance with US-FDA and EMA guidelines.

Concerning the in vivo pharmacokinetic study, the statistical significance between the results of the test groups receiving GFJ along with the cited drugs and the control group was assessed demonstrating that GFJ increased the plasma concentration of azithromycin, apixaban, and dexamethasone. Accordingly, this food–drug interaction requires cautious ingestion of GFJ in patients using (SARS-CoV-2) medications as it can produce negative effects in the safety of the drug therapy. A potential drug–drug interaction is also suggested between those medications requiring a suitable dose adjustment.

Simultaneous Determination of Thalidomide and Dexamethasone in Rat Plasma by Validated HPLC and HPTLC With Pharmacokinetic Study

Two validated chromatographic methods have been developed for the simultaneous determination of thalidomide (THD) and dexamethasone (DEX) in rat plasma using paracetamol (PAR) as an internal standard (IS). Chromatographic analysis was achieved firstly by HPLC method on C18 column (150 × 4.6 mm2 i.d., 5 μm) and a mobile phase composed of ethanol:water (containing 0.1% acetic acid) (70:30, v/v) at the flow rate of 0.6 mL min-1. The second method was HPTLC method which depended on using a developing system of methylene chloride:acetone:ethyl acetate (7:4:1, by volume). In both methods, PAR was used as an IS. The developed methods have been validated as per FDA guidelines. All parameters were tested using quality control samples (LQC, MQC and HQC). All the obtained parameters were within the acceptance criteria. In the same way, the two methods were successfully used to study the pharmacokinetic parameters of both THD and DEX after their intra-peritoneal administration. Moreover, results obtained after administration of each drug alone were compared to those obtained after their administration together. The drugs showed drug-drug interactions when administered in combination, meaning that monitoring of such combination is very important.