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Clinical data
Routes of
ATC code
Legal status
Legal status
  • In general: ℞ (Prescription only)
Pharmacokinetic data
Protein binding90%
Metabolism<30% hepatic
Elimination half-life0.5 hours
ExcretionBiliary and renal
  • (2S,5R,6R)-6-[(2-ethoxy-1-naphthoyl)amino]-3,3-dimethyl-7-oxo-4-thia-1-azabicyclo[3.2.0]heptane-2-carboxylic acid
CAS Number
PubChem CID
CompTox Dashboard (EPA)
ECHA InfoCard100.005.174 Edit this at Wikidata
Chemical and physical data
Molar mass414.48 g·mol−1
3D model (JSmol)
  • O=C(O)[C@@H]3N4C(=O)[C@@H](NC(=O)c2c1ccccc1ccc2OCC)[C@H]4SC3(C)C
  • 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 checkY

Nafcillin sodium is a narrow-spectrum[1] beta-lactam antibiotic[2] 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.

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.[3]


Nafcillin is indicated in the treatment of staphylococcal infections, except those caused by MRSA.[4]

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.[5]


As with all penicillins, serious life-threatening allergic reactions can occur. [citation needed]

Milder side-effects include:


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.[7]

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.[citation needed]


  1. ^ Palmer DL, Pett SB, Akl BF (March 1995). "Bacterial wound colonization after broad-spectrum versus narrow-spectrum antibiotics". The Annals of Thoracic Surgery. 59 (3): 626–631. doi:10.1016/0003-4975(94)00992-9. PMID 7887701.
  2. ^ Tan AK, Fink AL (January 1992). "Identification of the site of covalent attachment of nafcillin, a reversible suicide inhibitor of beta-lactamase". The Biochemical Journal. 281 (Pt 1): 191–196. doi:10.1042/bj2810191. PMC 1130660. PMID 1731755.
  3. ^ Viehman JA, Oleksiuk LM, Sheridan KR, Byers KE, He P, Falcione BA, Shields RK (May 2016). "Adverse Events Lead to Drug Discontinuation More Commonly among Patients Who Receive Nafcillin than among Those Who Receive Oxacillin". Antimicrobial Agents and Chemotherapy. 60 (5): 3090–3095. doi:10.1128/AAC.03122-15. PMC 4862451. PMID 26976858.
  4. ^ Pham P, Bartlett JG (January 2, 2009). "Nafcillin". Point-of-Care Information Technology ABX Guide. Johns Hopkins University. Retrieved on July 10, 2009. Freely available with registration.
  5. ^ Bonow RO, Carabello BA, Kanu C, de Leon AC, Faxon DP, Freed MD, et al. (August 2006). "ACC/AHA 2006 guidelines for the management of patients with valvular heart disease: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (writing committee to revise the 1998 Guidelines for the Management of Patients With Valvular Heart Disease): developed in collaboration with the Society of Cardiovascular Anesthesiologists: endorsed by the Society for Cardiovascular Angiography and Interventions and the Society of Thoracic Surgeons". Circulation. 114 (5): e84-231. doi:10.1161/CIRCULATIONAHA.106.176857. PMID 16880336.
  6. ^ Mohr JA, Clark RM, Waack TC, Whang R (August 1979). "Nafcillin-associated hypokalemia". JAMA. 242 (6): 544. doi:10.1001/jama.1979.03300060046028. PMID 448989.
  7. ^ Lang CC, Jamal SK, Mohamed Z, Mustafa MR, Mustafa AM, Lee TC (June 2003). "Evidence of an interaction between nifedipine and nafcillin in humans". British Journal of Clinical Pharmacology. 55 (6): 588–590. doi:10.1046/j.1365-2125.2003.01789.x. PMC 1884262. PMID 12814453.