difelikefalin difelikefalin difelikefalin, sold under the brand name korsuva, is an analgesic opioid peptide used for the treatment of moderate to severe itching. it acts as a peripherally specific, highly selective agonist of the κ-opioid receptor (kor). difelikefalinclinical datatrade nameskorsuvaother namescr845, fe-202845, d-phe-d-phe-d-leu-d-lys-license data us dailymed: difelikefalin pregnancycategory au: b1 routes ofadministrationintravenousdrug classkappa opioid receptor agonistatc codev03ax04 (who) legal statuslegal status au: s4 (prescription only) ca: ℞-only us: ℞-only eu: rx-only pharmacokinetic databioavailability100% (iv)metabolismnot metabolizedelimination half-life2 hoursexcretionexcreted as unchangeddrug via bile and urineidentifiers iupac name 4-amino-1-amino]-3-phenylpropanoyl]amino]-4-methylpentanoyl]amino]hexanoyl]piperidine-4-carboxylic acid cas number1024828-77-0 yas salt: 1024829-44-4pubchem cid24794466as salt: 91864509drugbankdb11938as salt: dbsalt003191chemspider44208824uniina1u919mroas salt: 0p70ar5bybkeggd11111as salt: d10890chemblchembl3989915chemical and physical dataformulac36h53n7o6molar mass679.863 g·mol−13d model (jsmol)interactive imageas salt: interactive image smiles cc(c)c(c(=o)n(ccccn)c(=o)n1ccc(cc1)(c(=o)o)n)nc(=o)(cc2=cc=cc=c2)nc(=o)(cc3=cc=cc=c3)nas salt: cc(o)=o.cc(c)c(nc(=o)(cc1=cc=cc=c1)nc(=o)(n)cc1=cc=cc=c1)c(=o)n(ccccn)c(=o)n1ccc(n)(cc1)c(o)=o inchi inchi=1s/c36h53n7o6/c1-24(2)21-29(32(45)40-28(15-9-10-18-37)34(47)43-19-16-36(39,17-20-43)35(48)49)42-33(46)30(23-26-13-7-4-8-14-26)41-31(44)27(38)22-25-11-5-3-6-12-25/h3-8,11-14,24,27-30h,9-10,15-23,37-39h2,1-2h3,(h,40,45)(h,41,44)(h,42,46)(h,48,49)/t27-,28-,29-,30-/m1/s1key:fwmnvwwhgchhjj-skkkgajssa-nas salt: inchi=1s/c36h53n7o6.c2h4o2/c1-24(2)21-29(32(45)40-28(15-9-10-18-37)34(47)43-19-16-36(39,17-20-43)35(48)49)42-33(46)30(23-26-13-7-4-8-14-26)41-31(44)27(38)22-25-11-5-3-6-12-25;1-2(3)4/h3-8,11-14,24,27-30h,9-10,15-23,37-39h2,1-2h3,(h,40,45)(h,41,44)(h,42,46)(h,48,49);1h3,(h,3,4)/t27-,28-,29-,30-;/m1./s1key:mzwhrpkahcwtoi-kgurmgbcsa-n difelikefalin acts as an analgesic by activating kors on peripheral nerve terminals and kors expressed by certain immune system cells. activation of kors on peripheral nerve terminals results in the inhibition of ion channels responsible for afferent nerve activity, causing reduced transmission of pain signals, while activation of kors expressed by immune system cells results in reduced release of proinflammatory, nerve-sensitizing mediators (e.g., prostaglandins). difelikefalin was approved for medical use in the united states in august 2021. the u.s. food and drug administration considers it to be a first-in-class medication. society and culture legal status on 24 february 2022, the committee for medicinal products for human use (chmp) of the european medicines agency adopted a positive opinion, recommending the granting of a marketing authorization for the medicinal product kapruvia, intended for treatment of moderate-to-severe pruritus associated with chronic kidney disease. the applicant for this medicinal product is vifor fresenius medical care renal pharma france. difelikefalin was approved for medical use in the european union in april 2022. research it is under development by cara therapeutics as an intravenous agent for the treatment of postoperative pain. an oral formulation has also been developed. due to its peripheral selectivity, difelikefalin lacks the central side effects like sedation, dysphoria, and hallucinations of previous kor-acting analgesics such as pentazocine and phenazocine. in addition to use as an analgesic, difelikefalin is also being investigated for the treatment of pruritus (itching). difelikefalin has completed phase ii clinical trials for postoperative pain and has demonstrated significant and "robust" clinical efficacy, along with being safe and well tolerated. it has also completed a phase iii clinical trial for uremic pruritus in hemodialysis patients.