nafcillin nafcillin nafcillin sodium is a narrow-spectrum beta-lactam antibiotic of the penicillin class. as a beta-lactamase-resistant penicillin, it is used to treat infections caused by gram-positive bacteria, in particular, species of staphylococci that are resistant to other penicillins. nafcillinclinical dataahfs/drugs.commonographmedlineplusa685019routes ofadministrationim, ivatc codej01cf06 (who) legal statuslegal status in general: ℞ (prescription only) pharmacokinetic dataprotein binding90%metabolism<30% hepaticelimination half-life0.5 hoursexcretionbiliary and renalidentifiers iupac name (2s,5r,6r)-6--3,3-dimethyl-7-oxo-4-thia-1-azabicycloheptane-2-carboxylic acid cas number985-16-0 ypubchem cid8982drugbankdb00607 ychemspider8634 yuniisy07234ttschebichebi:7447 ychemblchembl1443 ycomptox dashboard (epa)dtxsid8023343 echa infocard100.005.174 chemical and physical dataformulac21h22n2o5smolar mass414.48 g·mol−13d model (jsmol)interactive image smiles o=c(o)3n4c(=o)(nc(=o)c2c1ccccc1ccc2occ)4sc3(c)c inchi inchi=1s/c21h22n2o5s/c1-4-28-13-10-9-11-7-5-6-8-12(11)14(13)17(24)22-15-18(25)23-16(20(26)27)21(2,3)29-19(15)23/h5-10,15-16,19h,4h2,1-3h3,(h,22,24)(h,26,27)/t15-,16+,19-/m1/s1 ykey:gpxlmghlhqjagz-jtdstzfvsa-n y (verify) nafcillin is considered therapeutically equivalent to oxacillin, although one retrospective study found greater rates of hypokalemia and acute kidney injury in patients taking nafcillin compared to patients taking oxacillin. indications nafcillin is indicated in the treatment of staphylococcal infections, except those caused by mrsa. u.s. clinical practice guidelines recommend either nafcillin or oxacillin as the first-line treatment of choice for staphylococcal endocarditis in patients without artificial heart valves. side-effects as with all penicillins, serious life-threatening allergic reactions can occur. milder side-effects include: hypokalemia nausea and vomiting diarrhea, often due to suppression of normal gastrointestinal bacteria, which, on occasion, leads to a more serious super-infection with an organism like clostridium difficile abdominal pain yeast infections (thrush) affecting the mouth and tongue or vagina agranulocytosis, neutropenia interactions there is evidence that nafcillin induces cytochrome p-450 enzymes, specifically cyp2c9. several drugs with a narrow therapeutic window, such as warfarin and nifedipine, are metabolized by cyp2c9. nafcillin contains salts added as stability media. these added salts could cause edema or fluid accumulation. it would be prudent to avoid this medication if there were a concern for a congestive heart failure or kidney disease.