Identification of Metoprolol Tartrate-Derived Reactive Metabolites Possibly Correlated with Its Cytotoxicity

Silicon-Based Piezo Micropumps Enable Fully Flexible Drug Delivery Patterns

Drug release plays a crucial role in drug delivery. While current formulation approaches are capable of coarse-tuning the release profile, their precision and reproducibility are limited by the physicochemical properties of the excipients and active pharmaceutical ingredient (API). Innovative and advanced approaches are urgently needed, especially for site-specific targeting of drugs and to address their pharmacological requirements for optimal therapy. The 5 × 5 × 0.6 mm3 piezoelectric micropump developed by Fraunhofer EMFT was designed to enable precise drug delivery in a low volume format. In this study, we investigated the ability of the micropump to deliver solutions of highly soluble APIs using a wide range of customized pump profiles. Additionally, we examined the ability of the micropump to deliver suspensions containing various defined particle sizes. While results for suspensions indicate that pumping performance is highly dependent on the size and concentration of the suspended particles, results with API solutions demonstrate high precision and reproducibility of release, coupled with maximum flexibility in the release profile of the API. The piezoelectric micropump thus lays the cornerstone in the development of a wide range of innovative drug delivery profiles, enabling customized release profiles to be programmed and thus paving the way to fully personalized medicine.

Metabolic Activation and Cytotoxicity of Gramine Mediated by CYP3A in Rats

Gramine (GRM), which occurs in Gramineae plants, has been developed to be a biological insecticide. Exposure to GRM was reported to induce elevations of serum ALT and AST in rats, but the mechanisms of the observed hepatotoxicity have not been elucidated. The present study aimed to identify reactive metabolites that potentially participate in the toxicity. In rat liver microsomal incubations fortified with glutathione or N-acetylcysteine, one oxidative metabolite (M1), one glutathione conjugate (M2), and one N-acetylcysteine conjugate (M3) were detected after exposure to GRM. The corresponding conjugates were detected in the bile and urine of rats after GRM administration. CYP3A was the main enzyme mediating the metabolic activation of GRM. The detected GSH and NAC conjugates suggest that GRM was metabolized to a quinone imine intermediate. Both GRM and M1 showed significant toxicity to rat primary hepatocytes.

Metabolic Activation of Pesticide Isoprocarb Mediated by CYP3A4 and the Possible Correlation with Its Cytotoxicity

Isoprocarb (IPC), one of the most important carbamate pesticides, is used to control pests, such as rice planthoppers in crops. Studies have found that IPC induced hepatotoxicity in poultry chicken. However, the mechanisms of IPC-induced hepatotoxicity are unclear. The objectives of this study were to characterize reactive metabolites of IPC in vitro and in vivo, to identify cytochrome P450 enzymes for metabolic activation, and to define a possible correlation between the metabolic activation and cytotoxicity of IPC. In GSH- or NAC-supplemented microsomal incubations, one GSH conjugate (M6) and two NAC conjugates (M7 and M8) were detected after exposure to IPC. The corresponding GSH conjugate and NAC conjugates were found in the liver homogenates and urine of mice after IPC administration. IPC was found to be metabolized to a quinone intermediate reactive to GSH in vitro and in vivo. IPC was found to induce marked cytotoxicity in cultured mouse primary hepatocytes. Ketoconazole, a selective CYP3A4/5 enzyme inhibitor, attenuated the susceptibility of hepatocytes to IPC cytotoxicity.

Non-innocuous Consequences of Metabolic Oxidation of Alkyls on Arenes

Reactive metabolite (RM) formation is widely accepted as playing a pivotal role in causing adverse idiosyncratic drug reactions, with most attention paid to drug-induced liver injury. Mechanisms of RM formation are determined by the drug's properties in relation to human enzymes transforming the drug. This Perspective focuses on enzymatic oxidation of alkyl groups on aromatics leading to quinone methides and benzylic alcohol sulfates as RMs, a topic that has not received very much attention. Unlike previous overviews, we will include in our Perspective several fulvene-like methides such as 3-methyleneindole. We also speculate that a few older drugs may form non-reported methides of this class. In addition, we report a few guiding DFT calculations of changes in free energy on going from a benzylic alcohol to the corresponding methide. Particularly facile reactions of 2-aminothiazole-5-methanol and 4-aminobenzyl alcohol are noted.