Replicates Number for Drug Stability Testing during Bioanalytical Method Validation—An Experimental and Retrospective Approach

Background: The stability of a drug or metabolites in biological matrices is an essential part of bioanalytical method validation, but the justification of its sample size (replicates number) is insufficient. The international guidelines differ in recommended sample size to study stability from no recommendation to at least three quality control samples. Testing of three samples may lead to results biased by a single outlier. We aimed to evaluate the optimal sample size for stability testing based on 90% confidence intervals. Methods: We conducted the experimental, retrospective (264 confidence intervals for the stability of nine drugs during regulatory bioanalytical method validation), and theoretical (mathematical) studies. We generated experimental stability data (40 confidence intervals) for two analytes—tramadol and its major metabolite (O-desmethyl-tramadol)—in two concentrations, two storage conditions, and in five sample sizes (n = 3, 4, 5, 6, or 8). Results: The 90% confidence intervals were wider for low than for high concentrations in 18 out of 20 cases. For n = 5 each stability test passed, and the width of the confidence intervals was below 20%. The results of the retrospective study and the theoretical analysis supported the experimental observations that five or six repetitions ensure that confidence intervals fall within 85–115% acceptance criteria. Conclusions: Five repetitions are optimal for the assessment of analyte stability. We hope to initiate discussion and stimulate further research on the sample size for stability testing.

Tandem Mass Spectrometry (MS/MS) in the Preclinical Pharmacokinetic Study of a Highly Prescribed SNRI Drug for Depression and Its Application to Oral Extended Release Solid Dosage Formulations in Rabbits

Preclinical pharmacokinetic (pK) studies in animal models during the formulation development phase give preliminary evidence and near clear picture of the pK behavior of drug and/or its dosage forms prior to clinical studies on humans and help in tailoring of the dosage form according to the expected and requisite clinical behavior. The present work reports first of its kind preclinical pK study on oral extended release (ER) solid dosage formulations of venlafaxine (VEN) in New Zealand White rabbits. The VEN is a highly prescribed and one of the safest and most effective therapeutic agents used in the treatment different types of depression disorders worldwide. The LC-MS/MS bioanalytical method developed for this purpose demonstrated enough reliability in simultaneously quantitating VEN and its equipotent metabolite O-desmethylvenlafaxine (ODV) in rabbit plasma. The method described uses solid phase extraction for sample preparation followed by an ultra-fast LC-MS/MS analysis. The chromatographic separation was achieved isocratically with a predominantly polar mobile phase by employing RPLC. The triple quadrupole LC/MS/MS system operated in MRM mode used an ESI probe as an ion source in positive polarity. The validation results are within the permissible limits of US FDA recommendations and acceptance criteria for bioanalytical method validation.

Sensitive UHPLC-MS/MS technique for monitoring Levothyroxine (T4) in human serum against endogenous thyroxin level

Background: Levothyroxine is a synthetic thyroid hormone that is chemically identical to Thyroxine (T4), which is secreted by the follicular cells of the thyroid gland. Levothyroxine is used to treat deficiency of thyroid hormone and to prevent the recurrence of thyroid cancer. Levothyroxine is present endogenously in human body. Method: It requires treated matrix for the preparation of calibration curve standard and quality control samples. The method was developed using LC-MS/MS and validated in human charcoal stripped serum. Charcoal stripped matrix was used for the preparation of Calibration curve standards and Quality control samples. Method involves Solid-Phase Extraction technique. Levothyroxine D3 used as an internal standard (ISTD). Result: Chromatographic separation was achieved using reversed phase analytical column Gemini NX-C18 110Å, 3µm (50x3.6) mm. Mobile phase consisted of acetonitrile and water in a ratio of 70:30 with 150µL of formic acid in 1000 mL of mobile phase. Mobile phase achieved shorter run-time of 0.9 minute due to use of Ultra-high performance liquid chromatography (UHPLC). Positive electro-spray ionization technique detected MRM ion pair transitions 777.60→731.65 for Levothyroxine and 780.70→734.6 for Levothyroxine- D3 (ISTD) were used. AB SCIEX Triple Quad™ API-4000 LC-MS/MS system and the bioanalytical method with 10ng/mL as limit of quantification has been applied successfully to pharmacokinetics studies. Conclusion: Chromatographic separation was achieved using reversed phase analytical column Gemini NX-C18 110Å, 3µm (50x3.6) mm. Mobile phase consisted of acetonitrile and water in a ratio of 70:30 with 150µL of formic acid in 1000 mL of mobile phase. Mobile phase achieved shorter run-time of 0.9 minute due to use of Ultra-high performance liquid chromatography (UHPLC). Positive electro-spray ionization technique detected MRM ion pair transitions 777.60→731.65 for Levothyroxine and 780.70→734.6 for Levothyroxine- D3 (ISTD) were used. AB SCIEX Triple Quad™ API-4000 LC-MS/MS system and the bioanalytical method with 10ng/mL as limit of quantification has been applied successfully to pharmacokinetics studies.

LC–MS/MS bioanalytical method for quantification of binimetinib and venetoclax, and their pharmacokinetic interaction

Aim: Because of several prospective benefits, binimetinib (BMT)-venetoclax (VTC) combination can be a better therapeutic strategy to treat cancer. Results: An LC–MS/MS method for simultaneous quantification of BMT and VTC in rat plasma has been developed and validated. Specificity, accuracy, precision and stability results met the acceptance criteria for validation. Accuracy and precisions at all quality control levels were <15%. The study revealed that co-administration of BMT and VTC has no significant effect on their pharmacokinetics. Conclusion: The developed method can provide accurate results for quantification of BMT and VTC over the range of 5–500 ng/ml. The reported pharmacokinetic interaction study results will be useful for future consideration of the combined treatment of BMT and VTC in anticancer chemotherapy regimens.

BIOAVAILABILITY ENHANCEMENT BY FLOATING MICROBALLOONS OF DIPYRIDAMOLE AND CLOPIDOGREL: IN VIVO PHARMACOKINETIC STUDY

Objective: In vivo pharmacokinetic studies of clopidogrel and dipyridamole floating microballoons to check their bioavailability enhancement. Methods: The bioanalytical method development was carried by using HPLC with column Poroshell 120 EC-C 18; 4.6x100 mm. The in vivo pharmacokinetic studies were performed in Wistar male rats and the obtained data from the pharmacokinetic parameters were analyzed using PK Solver software. Results: The developed bioanalytical method was found to be linear in the concentration range of 1-100 ng/ml for clopidogrel bisulfate and 0.02-4µg/ml for dipyridamole with correlation coefficient of 0.9993 and 0.9987 respectively. The study results showed that the method was simple, linear, accurate and precise. The in vivo studies indicated that the AUC was found to be increased by 33.3% and 154.5% for clopidogrel and dipyridamole micro balloons, respectively, when compared to their pure drugs. Conclusion: The bioanalytical methods development and their validation parameters indicated that the methods are accurate, precise and linear in the studied range of concentrations. In vivo test results infer to the effective, sustained release of both the drugs when formulated as micro balloons and increase in the absorption, thereby enhancing the bioavailability of the drugs. The pharmacokinetic studies also confirmed the increase in the mean residence time of the drugs when formulated as floating microballoons.