Editing Fentanyl (section)

=== Structure-activity ===
[[File:Fentanyl numbering.svg|class=skin-invert-image|right|thumb|The chemical structure of fentanyl has been used as a basis in modern chemistry for the discovery and nomenclature of many new fentanyl analogues, sometimes called fentalogs.]]

The structures of opioids share many similarities. Whereas opioids like [[codeine]], [[hydrocodone]], [[oxycodone]], and [[hydromorphone]] are synthesized by simple modifications of morphine, fentanyl, and its relatives are synthesized by modifications of [[meperidine]].<ref name="Hemmings_2018">{{cite book | vauthors = Hemmings HC, Egan TD |date = 19 October 2018 |title=Pharmacology and Physiology for Anesthesia: Foundations and clinical application |isbn=978-0-323-56886-9 |edition=2nd |location=Philadelphia | publisher = Elsevier |oclc=1063667873}}</ref> Meperidine is a fully synthetic opioid, and other members of the phenylpiperidine family like alfentanil and sufentanil are complex versions of this structure.<ref name="Hemmings_2018"/>

Like other opioids, fentanyl is a weak [[Base (chemistry)|base]] that is highly [[Lipophilicity|lipid-soluble]], [[Plasma protein binding|protein-bound]], and protonated at [[PH#pH of various body fluids|physiological pH]].<ref name="Hemmings_2018"/> All of these factors allow it to rapidly cross [[Cell membrane|cellular membranes]], contributing to its quick effect in the body and the [[central nervous system]].<ref name="Mayes_2006"/><ref name="Yaksh_2011"/>