Side Effects for Nafcillin Injection
Body As A Whole
The reported incidence of allergic reactions to penicillin ranges from 0.7 to 10 percent (see WARNINGS). Sensitization is usually the result of treatment, but some individuals have had immediate
reactions to penicillin when first treated. In such cases, it is thought that the patients may have had prior
exposure to the drug via trace amounts present in milk or vaccines. Two types of allergic reactions to
penicillins are noted clinically, immediate and delayed.
Immediate reactions usually occur within 20 minutes of administration and range in severity from
urticaria and pruritus to angioedema, laryngospasm, bronchospasm, hypotension, vascular collapse, and
death. Such immediate anaphylactic reactions are very rare (see WARNINGS) and usually occur after
parenteral therapy but have occurred in patients receiving oral therapy. Another type of immediate
reaction, an accelerated reaction, may occur between 20 minutes and 48 hours after administration and
may include urticaria, pruritus, and fever.
Although laryngeal edema, laryngospasm, and hypotension occasionally occur, fatality is uncommon.
Delayed allergic reactions to penicillin therapy usually occur after 48 hours and sometimes as late as 2
to 4 weeks after initiation of therapy. Manifestations of this type of reaction include serum sickness-like
symptoms (i.e., fever, malaise, urticaria, myalgia, arthralgia, abdominal pain) and various skin rashes.
Nausea, vomiting, diarrhea, stomatitis, black or hairy tongue, and other symptoms of gastrointestinal
irritation may occur, especially during oral penicillin therapy.
Local Reactions
Pain, swelling, inflammation, phlebitis, thrombophlebitis, and occasional skin sloughing at the injection
site have occurred with intravenous administration of nafcillin (see DOSAGE AND ADMINISTRATION). Severe tissue necrosis with sloughing secondary to subcutaneous extravasation
of nafcillin has been reported.
Nervous System Reactions
Neurotoxic reactions similar to those observed with penicillin G could occur with large intravenous or
intraventricular doses of nafcillin especially in patients with concomitant hepatic insufficiency and renal
dysfunction (see PRECAUTIONS).
Urogenital Reactions
Renal tubular damage and interstitial nephritis have been associated with the administration of nafcillin.
Manifestations of this reaction may include rash, fever, eosinophilia, hematuria, proteinuria, and renal
insufficiency.
Hepatic Reactions
Elevation of liver transaminases and/or cholestasis may occur, specifically with administration of high
doses of nafcillin.
Gastrointestinal Reactions
Pseudomembranous colitis has been reported with the use of nafcillin. The onset of pseudomembranous
colitis symptoms may occur during or after antibiotic treatment (see WARNINGS).
Metabolic Reactions
Agranulocytosis, neutropenia, and bone marrow depression have been associated with the use of
nafcillin.
Drug Interactions for Nafcillin Injection
Tetracycline, a bacteriostatic antibiotic, may antagonize the bactericidal effect of penicillin, and
concurrent use of these drugs should be avoided.
Nafcillin in high dosage regimens, i.e., 2 grams every 4 hours, has been reported to decrease the
effects of warfarin. When nafcillin and warfarin are used concomitantly, the prothrombin time should be
closely monitored and the dose of warfarin adjusted as necessary. This effect may persist for up to 30
days after nafcillin has been discontinued.
Nafcillin when administered concomitantly with cyclosporine has been reported to result in
subtherapeutic cyclosporine levels. The nafcillin-cyclosporine interaction was documented in a patient
during two separate courses of therapy. When cyclosporine and nafcillin are used concomitantly in
organ transplant patients, the cyclosporine levels should be monitored.