Rapid and sensitive UPLC-MS/MS method for the determination of etodolac in small-volume rat plasma: Application to rat real samples

Dual Delivery of Cyclosporin A and Etodolac Using Polymeric Nanocapsules in a Rabbit Eye Model: Ocular Biodistribution and Pharmacokinetic Study

Purpose: Commercially available eye drops are loaded only with a single drug. By using the polymeric nanocapsules, dual delivery of 0.05% w/w cyclosporin A (CsA) and 0.2% w/w etodolac (Edc) was achieved. An ultraperformance liquid chromatography/tandem mass spectrometry (UPLC-MS/MS) method was developed for determining simultaneously the biodistribution and pharmacokinetic profile of CsA and Edc in ocular tissues. Methods: After one single drop instillation of nanocapsules into healthy right eyes of rabbits, the eyeballs were enucleated at 5, 15, 30, 60, and 90 min time periods to separate the 5 different ocular tissues. A liquid/liquid extraction method was used for ocular sample extraction using darunavir as internal standard. Using 3 diverse conditions such as bench-top, autosampler, and freeze-thaw, the stability of the analytes at 3 quality control samples in ocular tissues was also checked. Results: Intra- and interday precisions for both CsA and Edc in multiple ocular tissues were <10.32%, and the accuracy was <11.98%. The % bias and % RSD values for CsA and Edc were found within the acceptable limit of ±15%. The highest C_max values were attained in cornea for both the drugs at 60 min postinstillation time point. Despite molecular size and structural differences, both CsA and Edc after liberation from nanocapsule drops can permeate into the tissues of the anterior as well as posterior segments of the eye. Conclusion: The biodistribution and pharmacokinetic data might help and strengthen our understanding of synergetic anti-inflammatory activity of CsA and Edc from nanocapsules after its ocular topical application for managing keratoconjunctivitis sicca.

Determination and pharmacokinetic study of riociguat by UPLC-MS/MS in human plasma

Pulmonary hypertension (PH) is frequent in the general population and is linked to an increased risk of death. Riociguat is a kind of endothelin receptor antagonist that is often used to treat PH. For pharmacokinetic studies and the determination of riociguat in PH patients, a new, quick, easy, and sensitive UPLC-MS/MS approach was designed and validated. Riociguat and irbesartan (IS) were detected using ESI in positive ion and multiple reaction monitoring mode, respectively, by monitoring the mass transitions m/z 423.0 → 391.0 and 429.1 → 206.9. A reverse-phase C18 column (5 μm, 4.6 × 150 mm) was used with an isocratic mobile phase of water containing 0.1 % formic acid-acetonitrile (25:75, v/v) at a flow rate of 1 ml/min for chromatographic separation. In the range of 5-400 ng/ml, the calibration curve was linear and had a good correlation coefficient (0.9972). This is the first UPLC-MS/MS technique that has been developed and validated for determining riociguat from human plasma. The developed analytical method was extensively validated for linearity, selectivity, specificity, accuracy, precision, sensitivity, stability, matrix effect and recovery, according to FDA criteria. The devised approach was successfully used for a pharmacokinetic research and riociguat determination in PH patients.

A Sensitive UPLC-MS/MS Method for the Determination of Flurbiprofen in Rat Plasma: Application to Real Sample

For the quantification of flurbiprofen in rat plasma, a simple UPLC-MS/MS method with high sensitivity and short retention time for flurbiprofen was developed and validated using specific parameters. Etodolac was used as internal standard. The transitions (precursor to the product) of flurbiprofen and internal standard were obtained using the electrospray ionization in the negative ion multiple reaction monitoring mode, 243.2 → 199.2, 286.2 → 212.1, respectively. For chromatographic separation, C18 column was used for the stationary phase and gradient elution was used for the mobile phase. This mobile phase consisted of a methanol (A) and a 5 mM ammonium formate solution (B), which varied at a flow rate of 0.4 mL/min. For flurbiprofen, LLOQ was determined as 5 ng/mL. Quantification of flurbiprofen in the rat plasma with a linear calibration curve of 5-5000 ng/mL (r > 0.9991 for plasma) is possible with a retention time of 1.89 min. The total analysis time of the method was 3 min. The proposed method was validated. The intraday and inter-day precision (RSD%) and accuracy (RE%) were within 10% in all cases for flurbiprofen. The stability of flurbiprofen was evaluated under conditions such as short-term, long-term, autosampler and freeze/thaw. After method validation, flurbiprofen was succesfully quantified in real rat plasma samples.