phaclofen phaclofen phaclofen, or phosphonobaclofen, is a selective antagonist for the gabab receptor. it was the first selective gabab antagonist discovered, but its utility was limited by the fact that it does not cross the blood brain barrier. phaclofen names iupac name phosphonic acid identifiers cas number 108351-35-5 y 3d model (jsmol) interactive image chemspider 1579 n iuphar/bps 1091 pubchem cid 1641 inchi inchi=1s/c9h13clno3p/c10-9-3-1-7(2-4-9)8(5-11)6-15(12,13)14/h1-4,8h,5-6,11h2,(h2,12,13,14) nkey: vsgngljpogudon-uhfffaoysa-n ninchi=1/c9h13clno3p/c10-9-3-1-7(2-4-9)8(5-11)6-15(12,13)14/h1-4,8h,5-6,11h2,(h2,12,13,14)key: vsgngljpogudon-uhfffaoyao smiles c1=cc(=cc=c1c(cn)cp(=o)(o)o)cl properties chemical formula c9h13clno3p molar mass 249.631 g/mol except where otherwise noted, data are given for materials in their standard state (at 25 °c , 100 kpa). n verify (what is yn ?) infobox references