fosamprenavir fosamprenavir fosamprenavir, sold under the brand names lexiva and telzir, is a medication used to treat hiv/aids. it is a prodrug of the protease inhibitor and antiretroviral drug amprenavir. it is marketed by viiv healthcare as the calcium salt. fosamprenavirclinical datatrade nameslexiva, telzirother namesfosamprenavir calcium (usan us)ahfs/drugs.commonographmedlineplusa604012license data eu ema: by inn pregnancycategory au: b3 routes ofadministrationby mouthatc codej05ae07 (who) legal statuslegal status ca: ℞-only uk: pom (prescription only) us: ℞-only eu: rx-only pharmacokinetic databioavailabilityunknownprotein binding90%metabolismhydrolysed to amprenavir and phosphate in gi tract epitheliumelimination half-life7.7 hoursexcretionfecal (as metabolites of amprenavir)identifiers iupac name amino)-4-phenylbutan-2-yl]oxy}phosphonic acid cas number226700-79-4 yas salt: 226700-81-8 ypubchem cid131536as salt: 131535drugbankdb01319 yas salt: dbsalt001228chemspider116245 yas salt: 116244uniiwou1621eegas salt: id1gu2627n ykeggd02497 nas salt: d03835chebichebi:82941chemblchembl1664 yas salt: chembl1200734niaid chemdb082186comptox dashboard (epa)dtxsid2048296 chemical and physical dataformulac25h36n3o9psmolar mass585.61 g·mol−13d model (jsmol)interactive image smiles o=c(o1ccoc1)n(cc2ccccc2)(op(=o)(o)o)cn(cc(c)c)s(=o)(=o)c3ccc(n)cc3 inchi inchi=1s/c25h36n3o9ps/c1-18(2)15-28(39(33,34)22-10-8-20(26)9-11-22)16-24(37-38(30,31)32)23(14-19-6-4-3-5-7-19)27-25(29)36-21-12-13-35-17-21/h3-11,18,21,23-24h,12-17,26h2,1-2h3,(h,27,29)(h2,30,31,32)/t21-,23-,24+/m0/s1 ykey:mlbvmoweqczncc-oemfjlhtsa-n yas salt: inchi=1s/c25h36n3o9ps.ca/c1-18(2)15-28(39(33,34)22-10-8-20(26)9-11-22)16-24(37-38(30,31)32)23(14-19-6-4-3-5-7-19)27-25(29)36-21-12-13-35-17-21;/h3-11,18,21,23-24h,12-17,26h2,1-2h3,(h,27,29)(h2,30,31,32);/q;+2/p-2/t21-,23-,24+;/m0./s1key:pmdqgymgqktcsx-hqroksdrsa-l ny (what is this?) (verify) fosamprenavir was approved for medical use in the united states in october 2003, and in the european union in july 2004. the human body metabolizes fosamprenavir in order to form amprenavir, which is the active ingredient. a head-to-head study with lopinavir showed the two drugs to have comparable potency, but patients on fosamprenavir tended to have a higher serum cholesterol. medical uses fosamprenavir is used for the treatment of hiv-1 infections, typically but not necessarily in combination with low-dose ritonavir or other antiviral drugs. adverse effects the most common adverse effect is diarrhea. other common side effects include headache, dizziness and exanthema, which is usually transient. severe allergic reactions (stevens–johnson syndrome) are rare. interactions amprenavir (the active metabolite of fosamrenavir, which is found in blood plasma, liver and other organs) is metabolized via the liver enzyme cyp3a4 and also weakly inhibits this enzyme. this means that combination with drugs that are also metabolized by cyp3a4 can increase their plasma concentrations and thus side effects; and combination with drugs that inhibit cyp3a4 can increase amprenavir concentrations. when combining fosamprenavir with low doses of the cyp3a4 inhibitor ritonavir, this interaction is intended as it allows for application of lower fosamprenavir doses. pharmacology fosamprenavir is quickly activated to amprenavir, even before it reaches the circulation. amprenavir is a hiv protease inhibitor. hiv-1 protease dimer with amprenavir (sticks) bound in the active site. pdb entry 3nu3