Related Experiment Video
Updated: Oct 15, 2026

Demonstration of the Sequence Alignment to Predict Across Species Susceptibility Tool for Rapid Assessment of Protein Conservation
Published on: February 10, 2023
How Subtle Molecular Differences in the Morphinan Opioid Antagonists Affect Their Physicochemical and In Vitro ADME
Sigal Saphier1, Ada Wenger1, Alexander Pevzner2
1Department of Organic Chemistry, Israel Institute for Biological Research, Ness-Ziona 74100, Israel.
Abstract:
Naloxone, naltrexone and nalmefene are closely related morphinan antagonists with comparable affinities to the μ-opioid receptor (MOR) but markedly different pharmacokinetics (PK) and metabolic fate. In this study, we evaluated their pharmacologically-relevant molecular/physicochemical properties, PAMPA-BBB (Parallel Artificial Membrane Permeability Assay for the Blood-Brain Barrier) permeability and in vitro metabolic stability to determine how subtle structural differences influence ADME-relevant properties. Moreover, the pharmacologically-relevant properties of these three antagonists were compared with those of the best-known synthetic opioid agonist, fentanyl. We found that the methyl-cyclopropyl versus allyl head group, as well as the C6-carbonyl versus C6-ethenyl group, dramatically influence all the above-mentioned properties and help explain the in vivo observed differences between these antagonists. These results may support the rational design of new and improved opioid antagonists with optimized PK properties.
More Related Videos
Related Concept Videos
Opioid Receptors: Overview
Opioid Analgesics: Synthetic and Semisynthetic Opioids
Adrenergic Agonists: Chemistry and Structure-Activity Relationship
Aromatic ring substitutions: Substituting the aromatic ring with –OH groups at positions 3 and 4 yields catecholamines (e.g., epinephrine), which have a high affinity for adrenoceptors. Hydrogen bonding between –OH groups and receptors enhances adrenergic activity.
Separation of the aromatic...
Opioid Analgesics: Morphine and Other Natural Cogeners
Analgesia and Pain Management
Drug-Receptor Interaction: Agonist
Agonists can bind to receptors in different ways. Some agonists bind directly to the receptor's active site, mimicking the endogenous ligand's action.

