In Vitro and In Vivo Analysis of Fentanyl and Fentalog Metabolites using Hyphenated Chromatographic Techniques: A Review

Fentanyl and non-pharmaceutical fentanyls (NPFs) have been responsible for numerous outbreaks of overdoses all over the United States since the 1970s. However, there has been a growing concern in recent years that NPFs are contributing to an alarming rise in the number of opioid-related overdoses.

Cloning of multiple opioid receptors has presented opportunities to investigate the mechanisms of multiple opioid receptor signaling and the regulation of these signals. The subsequent identification of receptor gene structures has also provided opportunities to study the regulation of receptor gene expression and to manipulate the concentration of the gene products in vivo. Thus, in the current review, we examine recent advances in the delineation basis for the multiple opioid receptor signaling, and their regulation at multiple levels. We discuss the use of receptor knockout animals to investigate the function and the pharmacology of these multiple opioid receptors. The reasons and basis for the multiple opioid receptor are addressed.