Nafcillin should generally not be administered to patients with a history of sensitivity to any penicillin.
Penicillin should be used with caution in individuals with histories of significant allergies and/or
asthma. Whenever allergic reactions occur, penicillin should be withdrawn unless, in the opinion of the
physician, the condition being treated is life-threatening and amenable only to penicillin therapy. The
use of antibiotics may result in overgrowth of nonsusceptible organisms. If new infections due to
bacteria or fungi occur, the drug should be discontinued and appropriate measures taken.
The liver/biliary tract is the primary route of nafcillin clearance. Caution should be exercised when
patients with concomitant hepatic insufficiency and renal dysfunction are treated with nafcillin.
Prescribing Nafcillin Injection, USP in the absence of a proven or strongly suspected bacterial infection
or a prophylactic indication is unlikely to provide benefit to the patient and increases the risk of the
development of drug-resistant bacteria.
Bacteriologic studies to determine the causative organisms and their susceptibility to the penicillinaseresistant
penicillins should be performed (see CLINICAL PHARMACOLOGY - Microbiology). In the
treatment of suspected staphylococcal infections, therapy should be changed to another active agent if
culture tests fail to demonstrate the presence of staphylococci.
Periodic assessment of organ system function including renal, hepatic, and hematopoietic should be
made during prolonged therapy with nafcillin. White blood cell and differential cell counts should be
obtained prior to initiation of therapy and periodically during therapy with nafcillin. Urinalysis, serum
blood urea nitrogen, and creatinine determinations should be performed at baseline and periodically
during therapy with nafcillin. Serum bilirubin, aspartate aminotransferase (AST), alanine
aminotransferase (ALT), alkaline phosphatase, and gamma glutamyl transferase should be obtained at
baseline and periodically during therapy, especially when using high nafcillin doses. In patients with
worsening hepatic function, the risk versus benefit of continued Nafcillin use should be re-evaluated.
Drug/Laboratory Test Interactions
Nafcillin in the urine can cause a false-positive urine reaction for protein when the sulfosalicyclic acid
test is used, but not with the dipstick.
Carcinogenesis, Mutagenesis, Impairment Of Fertility
No long term animal studies have been conducted with these drugs. Studies on reproduction (nafcillin)
in rats and mice reveal no fetal or maternal abnormalities before conception and continuously through
weaning (one generation).
Reproduction studies have been performed in the mouse with oral doses up to 20 times the human dose
and orally in the rat at doses up to 40 times the human dose and have revealed no evidence of impaired
fertility or harm to the rodent fetus due to nafcillin. There are, however, no adequate or well-controlled
studies in pregnant women. Because animal reproduction studies are not always predictive of human
response, nafcillin should be used during pregnancy only if clearly needed.
Penicillins are excreted in human milk. Caution should be exercised when penicillins are administered
to a nursing woman.
The liver/biliary tract is the principal route of nafcillin elimination. Because of immature hepatic and
renal function in pediatric patients, nafcillin excretion may be impaired. Safety and effectiveness in
pediatric patients have not been established for the use of intravenous nafcillin.
The potential for toxic effects in pediatric patients from chemicals that may leach from the single dose
premixed intravenous preparation in plastic containers has not been determined.
Clinical studies of Nafcillin Injection, USP did not include sufficient numbers of subjects aged 65 and
over to determine whether they respond differently from younger subjects. Other reported clinical
experience has not identified differences in responses between the elderly and younger patients. In
general, dose selection for an elderly patient should be cautious, usually starting at the low end of the
dosing range, reflecting the greater frequency of decreased hepatic, renal, or cardiac function, and of
concomitant disease or other drug therapy.
Nafcillin Injection, USP contains 76.6 mg (3.33 mEq) of sodium per gram. At the usual recommended
doses, patients would receive between 230 and 460 mg/day (10.0 and 20.0 mEq) of sodium. The
geriatric population may respond with a blunted natriuresis to salt loading. This may be clinically
important with regard to such diseases as congestive heart failure.