Pharmacology
Mechanism of action
Alvimopan is a competitive antagonist of the μ-opioid receptors (MOR) in the gastrointestinal tract, with a Ki of 0.2 ng/mL. Activation of these receptors by endogenous or exogenous agonists reduces gastrointestinal motility, and alvimopan blocks this effect. Like most other peripherally-selective MOR antagonists, such as naloxegel and methylnaltrexone, alvimopan is selective for peripheral receptors because is effluxed by P-glycoprotein, which  reduces its ability to cross the blood-brain barrier and affect the central nervous system. Pharmacokinetics
Absorption
Peak plasma concentration (Cmax) of alvimopan is reached approximately 2 hours after oral dosing, while the Cmax for metabolite occurs 36 hours after an oral dose. Alvimopans high affinity for the peripheral μ-receptor results in an absolute bioavailability less than 7%. Distribution
80% to 90% of systemically available alvimopan is bound to plasma protein. At steady state, the volume of distribution is approximately 30 liters. Metabolism
Alvimopan undergoes no significant hepatic metabolism, but is metabolized by intestinal flora. Gut metabolism produces an active metabolite with no clinically significant contribution to drug effect. Elimination
Alvimopan undergoes 35% renal excretion and greater than 50% biliary excretion. Drug metabolized by intestinal flora is excreted in the feces. Alvimopans half-life of elimination is 10 to 17 hours, while that of the gut metabolite is 10 to 18 hours. Dosing and administration
Alvimopan is required by the FDA to participate in Risk Evaluation and Mitigation Strategy (REMS) to ensure safe use. Alvimopan is only approved for short term use of no more than 15 doses.
Vilas, Román; Ceballos, Francisco C.; Al-Soufi, Laila; González-García, Raúl; Moreno, Carlos; Moreno, Manuel; Villanueva, Laura; Ruiz, Luis; Mateos, Jesús; González, David; Ruiz, Jennifer; Cinza, Aitor; Monje, Florencio; Álvarez, Gonzalo (17 November 2019). "Is the Habsburg jaw related to inbreeding?". Annals of Human Biology. 46 (7–8): 553–561. doi:10.1080/03014460.2019.1687752. PMID 31786955. S2CID 208536371. Vioarsdóttir, US; OHiggins, O; Stringer, C (2002). "A geometric morphometric study of regional differences in the ontogeny of the modern human facial skeleton". J. Anat. 201 (3): 211–229. doi:10.1046/j.1469-7580.2002.00092.x. PMC 1570912. PMID 12363273. Wolff, G; Wienker, T F; Sander, H (1 February 1993). "On the genetics of mandibular prognathism: analysis of large European noble families". Journal of Medical Genetics. 30 (2): 112–116. doi:10.1136/jmg.30.2.112. PMC 1016265. PMID 8445614. External links

 The dictionary definition of prognathism at Wiktionary