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Home / Drugs / Starting with N / Nafcillin

A semi-synthetic antibiotic related to penicillin. [PubChem]
Nafcillin sodium for injection
Nallpen In Plastic Container
CategoriesAnti-Bacterial Agents
ManufacturersWyeth ayerst laboratories
Apothecon inc div bristol myers squibb
Marsam pharmaceuticals llc
Sandoz inc
Baxter healthcare corp
PackagersBaxter International Inc.
Cardinal Health
Mead Johnson and Co.
SynonymsNafcilina [INN-Spanish]
Nafcillin Sodium
Nafcillin sodium salt
Nafcilline [INN-French]
Nafcillinum [INN-Latin]


For the treatment of infections caused by penicillinase-producing staphylococci which have demonstrated susceptibility to the drugs.


Nafcillin is a semisynthetic antibiotic substance derived from 6-amino-penicillanic acid. The drugs in this class are highly resistant to inactivation by staphylococcal penicillinase and are active against penicillinase-producing and non penicillinase-producing strains of Staphylococcus aureus. The penicillinase- resistant penicillins are active in vitro against a variety of other bacteria.

mechanism of action

Penicillinase-resistant penicillins exert a bactericidal action against penicillin-susceptible microorganisms during the state of active multiplication. All penicillins inhibit the biosynthesis of the bacterial cell wall.


Serious toxicity is unlikely following large doses of nafcillin. Acute ingestion of large doses of nafcillin may cause nausea, vomiting, diarrhea and abdominal pain. Acute oliguric renal failure and hematuria may occur following large doses.


Hepatic metabolism accounts for less than 30% of the biotransformation of most penicillins.

half life

The serum half-life of nafcillin administered by the intravenous route ranged from 33 to 61 minutes as measured in three separate studies.

route of elimination

Nafcillin is primarily eliminated by nonrenal routes, namely hepatic inactivation and excretion in the bile.

drug interactions

Cyclosporine: Nafcillin alters serum levels of cyclosporine

Demeclocycline: Possible antagonism of action

Doxycycline: Possible antagonism of action

Ethinyl Estradiol: This anti-infectious agent could decrease the effect of the oral contraceptive

Methotrexate: The penicillin increases the effect and toxicity of methotrexate

Minocycline: Possible antagonism of action

Telithromycin: Nafcillin may decrease the plasma concentration of Telithromycin. Consider alternate therapy.

Temsirolimus: Nafcillin may increase the metabolism of Temsirolimus decreasing its efficacy. Concomitant therapy should be avoided.

Tetracycline: Possible antagonism of action

Tramadol: Nafcillin may decrease the effect of Tramadol by increasing Tramadol metabolism and clearance.

Trazodone: The CYP3A4 inducer, Nafcillin, may decrease Trazodone efficacy by increasing Trazodone metabolism and clearance. Monitor for changes in Trazodone efficacy/toxicity if Nafcillin is initiated, discontinued or dose changed.

Verapamil: Nafcillin may decrease the serum concentration of Verapamil by increasing its metabolism via CYP3A4. Monitor for changes in the therapeutic/adverse effects of Verapamil if Nafcillin is initiated, discontinued or dose changed.

Warfarin: Nafcillin may increase the anticoagulant effect of warfarin increasing the risk of bleeding. Consider alternate therapy or monitor for changes in the therapeutic and adverse effects of warfarin if nafcillin is initiated, discontinued or dose changed.