Editing Loratadine (section)

=== Pharmacokinetics ===
Loratadine is given orally, is well absorbed from the gastrointestinal tract, and has rapid [[first-pass metabolism|first-pass hepatic metabolism]]; it is metabolized by [[isoenzyme]]s of the [[cytochrome P450]] system, including [[CYP3A4]], [[CYP2D6]], and, to a lesser extent, several others.<ref name=Foye>{{cite book | vauthors = Nelson WL | veditors = Williams DH, Foye WO, Lemke TL |title=Foye's principles of medicinal chemistry |publisher=Lippincott Williams & Wilkins |location=Hagerstown, MD |year=2002 |chapter=Antihistamines and related antiallergic and antiulcer agents |pages=805 |isbn=978-0-683-30737-5}}</ref><ref>{{cite journal | vauthors = Ghosal A, Gupta S, Ramanathan R, Yuan Y, Lu X, Su AD, Alvarez N, Zbaida S, Chowdhury SK, Alton KB | title = Metabolism of loratadine and further characterization of its in vitro metabolites | journal = Drug Metabolism Letters | volume = 3 | issue = 3 | pages = 162–70 | date = August 2009 | pmid = 19702548 | doi = 10.2174/187231209789352067 }}</ref> Loratadine is almost totally (97–99%) bound to [[plasma proteins]]. Its metabolite [[desloratadine]], which is largely responsible for the antihistaminergic effects, binds to plasma proteins by 73–76%.<ref name="Austria-Codex" />

Loratadine's peak effect occurs after 1–2 hours, and its biological [[half life]] is on average eight hours (range 3 to 20 hours) with [[desloratadine]]'s half-life being 27 hours (range 9 to 92 hours), accounting for its long-lasting effect.<ref>{{cite journal | vauthors = Affrime M, Gupta S, Banfield C, Cohen A | title = A pharmacokinetic profile of desloratadine in healthy adults, including elderly | journal = Clinical Pharmacokinetics | volume = 41 | issue = Suppl 1 | pages = 13–9 | year = 2002 | pmid = 12169042 | doi = 10.2165/00003088-200241001-00003 | s2cid = 25555379 }}</ref> About 40% is excreted as [[Biotransformation#Phase II reaction|conjugated metabolites]] into the urine, and a similar amount is excreted into the feces. Traces of unmetabolised loratadine can be found in the urine.<ref name="Austria-Codex" />

In structure, it is closely related to [[tricyclic antidepressant]]s, such as [[imipramine]], and is distantly related to the atypical [[antipsychotic]] [[quetiapine]].<ref name="pmid10444229">{{cite journal | vauthors = Kay GG, Harris AG | title = Loratadine: a non-sedating antihistamine. Review of its effects on cognition, psychomotor performance, mood and sedation | journal = Clinical and Experimental Allergy | volume = 29 | issue = Suppl 3 | pages = 147–50 | date = July 1999 | pmid = 10444229 | doi = 10.1046/j.1365-2222.1999.0290s3147.x | s2cid = 26012715 }}</ref>