Drug Metabolism Letters - Volume 14, Issue 2, 2021

Background: Kidney disease associated with cancer and anti-cancer therapies has been increasingly recognized in the field of onco-nephrology. In particular, drug-induced nephrotoxicity has important implications since most chemotherapeutic agents have a nephrotoxic potential. Also, standard creatinine clearance methods used for the measurement of kidney function have been questioned in cancer patients due to factors like low muscle mass and poor nutritional status. Overestimations of the glomerular filtration rate, not only can increase the nephrotoxic potential of different agents, but also further limit the use of first-line therapies. Objective: This review covers specifically the drug-induced thrombotic microangiopathy and its two pathophysiologic mechanisms which include immune or idiosyncratic reactions, and non-immune or dose-dependent ones. Conclusion: As novel cancer therapies are developed, it is paramount to pursue a better understanding of conventional and novel chemotherapeutic agents and their role in kidney disease.

Due to its easy availability, rapid and severe toxicity, and no specific antidote, aluminum phosphide has emerged as a lethal toxin, commonly used for suicidal intent in agricultural communities. Despite various advances in medicine, this compound’s toxicity is poorly understood, and it still has a very high case fatality rate with no definitive treatment options available. This review aims to understand the mechanism of toxicity, clinical toxidrome of acute aluminum phosphide poisoning, and the available therapeutic options, including recent advances. A literature review was performed searching PubMed, EMBASE Ovid, and Cochrane Library, using the following search items: (“aluminum phosphide poisoning” OR “aluminum phosphide poisoning toxicity” OR “aluminum phosphide ingestion”) AND (“management” OR “therapy” OR “treatment”). Selected articles were discussed amongst all the authors to shape this review. High case fatality rate and lack of any specific antidote are persisting challenges. Therapeutic measures need to be implemented from all fronts – reducing easy access to the poison, developing less toxic alternatives for use as a pesticide, and more studies directed at developing an effective reversal agent for phosphine. The advent of promising agents like glucose-insulin-potassium infusion and lipid emulsion is a new ray of hope in the complete recovery in this fatal poisoning. The need of the hour is to find an agent that rapidly and effectively reverses aluminum phosphide's toxic effects. Large multicenter controlled trials are required to establish the role of glucose-insulin-potassium and lipid emulsion.

Backgrounds: Plants and their derived products have been used in the traditional system of medicine for the treatment of various forms of human disorders since very ancient times. In the traditional system of medicine and modern allopathic medicine, numerous phytoconstituents have been used for the preparation of various types of formulation. Flavonoidal class phytochemicals are the main active phytoconstituents of plants, fruit, vegetables and beverages. Flavonoidal class phytochemicals are more referred as “nutraceuticals” due to their important pharmacological activities in the mammalian body. Methods: In order to understand the beneficial health effects of flavonoidal class chemical, the present work summarized the health beneficial aspects of pectolinarin. Present work summarized the medicinal importance, pharmacological activities and analytical aspects of pectolinarin with various experimental models and advance analytical methods. However, all the collected scientific information’s have been analyzed in the present work for their health beneficial potential. Results: From the analysis of all the collected scientific information in the present work, it was found that pectolinarin is an important phytochemical present in numerous medicinal plants but especially found in Cirsium japonicum, which is an important medicinal herb of Korea, China and Japan. Pharmacological activities data analysis signified the health beneficial potential of pectolinarin for their anti-rheumatoid arthritis, analgesic, anti-inflammatory, hepatoprotective, anti-diabetic, anti-tumor, anti-dengue, antiviral, neuroprotective and antidepressant activity. However, the effectiveness of pectolinarin in central nervous system, bone, liver and cancerous disorders have been also reported in the literature. Analysis of present scientific information revealed the health beneficial potential of pectolinarin in modern medicine due to their numerous pharmacological activities in different parts of biological systems. Due to their biological importance in food and human health, a better understanding of their biological activities indicates their potentials as therapeutic agents. Conclusion: Scientific data of the present work signified the biological potential and therapeutic benefit of pectolinarin.

Background: A group of substituted benzothiazoles from a research project was found to have low microsomal clearance. However, these compounds had very high clearance in vivo. Methods: In the present study, the clearance mechanism of two of the structural analogs, was investigated in vitro and in vivo. Results: In vitro studies showed the formation of corresponding non-P450 dependent oxidative metabolites in S9, cytosol, and hepatocytes. The in vitro formation of these metabolites was observed in mice, rats, non-human primates, and humans. The dog did not form the corresponding metabolites in any of the matrices. Inhibition studies with S9 fraction and incubation with human recombinant aldehyde oxidase (AO) showed that the formation of the corresponding metabolites was AO dependent. To investigate the role of this pathway in vivo, mice were dosed with compound A and bile and plasma were analyzed. Most of the metabolites in bile contained the AO-dependent oxidized benzothiazole moiety, indicating that metabolism involving AO was probably the main pathway for clearance. The same metabolites were also observed circulating in plasma. Mass spectrometric analysis of the metabolite showed that the oxidation was on the benzothiazole moiety, but the exact position could not be identified. Isolation of the metabolite of compound A and analysis by NMR confirmed the structure of the metabolite as C2 carbon oxidation of the thiazole ring resulting in carboxamide moiety. Further comparison of both metabolites with corresponding authentic standards confirmed the structures. Conclusion: To our knowledge, such an observation of in vitro and in vivo oxidation of substituted benzothiazole by AO has not been reported before. The results helped the medicinal chemists design compounds that avoid AO-mediated metabolism and with better ADME property.

Background: The pharmacodynamic effects of digoxin are susceptible to multiple factors, most notably, heart uptake of the digoxin dose and its concentration in the serum. Another important factor to mention is the renal function state of an individual. Objective: In this study, we aimed to develop a simple algorithm based on subsets of clinically relevant information, which will help to personalize digoxin based on pharmacokinetic (PK) approach which can help in marketing the appropriate utilization of this medication. Methods: This was a retrospective chart review and analysis of 48 patients who were admitted to the Drug and Poison Information center in Buraidah, Saudi Arabia, between January 2016 and April 2019. All pharmacokinetic parameters were added according to the C-peaks and C-troughs. MONOLiX® was used for data pharmacokinetic analysis. Results: Twenty-seven (56%) were males and twenty-one (44%) were females with an average age of 63.6 years across both genders. The mean volume of distribution was 496.6 litres with an average clearance of 6.6 L/h. For females, their average volume of distribution was slightly higher than that for males (526 litres compared to 473 litres). In addition, the clearance rate between both genders showed a 2.1 litre/hour discrepancy (7.8 L/h for females compared to 5.7 L/h for males). Conclusion: In order to individualize the digoxin dosage regimens, this model can be used to predict digoxin serum concentration. Further studies are needed to clarify the effects of nutritional status and co-administration of medications on digoxin pharmacokinetics.

Background: In the drug development process, an assessment of bioequivalence is an integral part. For the evaluation of generics against the comparator, average bioequivalence approach is the gold standard method. In the recent past, there were many discussions on whether we have the adequate tool to evaluate generics and thereby drug interchangeability (prescribability and switchability) issue is addressed as average bioequivalence approach just considers population mean. Hence, the alternative approaches like population bioequivalence and individual bioequivalence assessment approaches arise as different variances like inter/ intra-subject variance and subject- by-formulation variance along with population mean are considered. Objective: Methoxsalen, in combination with long-wave UVA radiation, is used in the symptomatic management certain psoriasis. The study was aimed to establish the bioequivalence (BE) of a newly developed methoxsalen capsule (MTX test) with that of a reference methoxsalen capsule (MTX reference) using multiple BE methods (i.e., average [ABE], population [PBE], and individual [IBE]) by utilizing a new LC-MS/MS method. Methods: This is an open-label, randomized, balanced, two-treatment, three-period, three-sequence, crossover, single-dose (20 mg, 2 × 10 mg capsules), comparative, oral BE study conducted in 52 healthy, adult males under fasting conditions. Along with various pharmacokinetic (PK) parameters ABE, PBE, and IBE were also determined in the single study. Results: A non-compartmental model best described the concentration-time data of both MTX test and reference. Both the formulations demonstrated nearly similar values of BE parameters (i.e., AUCo-t, AUC0-∞, Cmax, Tmax, and t^1/2). For MTX test, the observed Cmax, AUC0-t, and AUC0- ∞ were 125.16±81.53 ng/mL, 313.73±260.86 ng h/mL, and 321.25±271.85 ng h/mL, respectively. For MTX reference, the values were 127.63±71.60 ng/mL, 329.11±252.91 ng h/mL, and 335.48±264.54 ng h/mL, respectively. The bioanalytical method was validated over the concentration range 0.100-100.00ng/mL and the coefficient of determination (r2) was ≥ 0.9991. The sensitivity of the method was 0.100 ng/mL with the accuracy and precision values of 115% and 10.54%, respectively. Conclusion: A single dose of MTX test met the ABE criteria of 80.00% -125.00% for Cmax, AUCo- t, and AUC0-∞, against MTX reference. The study outcome by PBE and IBE approaches proved that MTX Test was bio-inequivalent to MTX reference. Using multiple BE assessment methods in a single BE study is a novel approach and may overcome shortcomings of conventional bioequivalence assessment methods.

Background: Methods to provide absolute quantitation of the administered drug and corresponding metabolites in tissue in a spatially resolved manner is a challenging but much needed capability in pharmaceutical research. Quantitative Whole-Body Autoradiography (QWBA) after a single- dose intravenous (3 mg/kg) and extravascular (30 mg/kg) administrations of an in vitro metabolically stable test compound (structure not reported here) indicated quick tissue distribution and excretion. Objective: Good bioavailability and short in vivo half-lives were determined formerly for the same test compound. For closing gaps in the understanding of pharmacokinetic data and in vitro results, radioactive hot spots on whole-body tissue sections had been profiled. Methods: Punches from selected tissue regions containing high radioactivity in the tissue sections previously analyzed by QWBA were extracted by a highly organic solvent and analyzed without any consecutive sample preparation step, applying Ultra High Performance Liquid Chromatography- Mass Spectrometry (UHPLC-MS) and off-line radioanalysis to maximize signal levels for metabolite identification and profiling. Results: The analysis revealed that the test compound was metabolized intensively by phase I reactions in vivo and the metabolites formed were excreted in bile and urine. The predominant metabolites showed abundant signal intensities both by MS and by radioanalysis but the MS signal intensities generally underestimated the real abundances of metabolites relative to the unchanged drug. Conclusion: This work illustrates that maximizing the sensitivity of tissue punch radioanalysis and the combination with UHPLC-MS leads to a better insight into pharmacokinetic processes by providing quantitative data with high molecular selectivity.