Nafcillin

Nafcillin is indicated in the treatment of infections caused by penicillinase-producing staphylococci which have demonstrated susceptibility to the drug. Culture and susceptibility tests should be performed initially to determine the causative organism and its susceptibility to the drug. Nafcillin should not be used in infections caused by organisms susceptible to penicillin G. If the susceptibility tests indicate that the infection is due to methicillin-resistant Staphylococcus species, therapy with Nafcillin Injection, USP should be discontinued and alternative therapy provided. To reduce the development of drug-resistant bacteria and maintain the effectiveness of Nafcillin Injection, USP and other antibacterial drugs, Nafcillin Injection, USP should be used only to treat or prevent infections that are proven or strongly suspected to be caused by susceptible bacteria.

Nafcillin Injection, USP supplied as a premixed frozen solution is to be administered as an intravenous infusion. The usual I.V. dosage for adults is 500 mg every 4 hours. For severe infections, 1 g every 4 hours is recommended. Administer slowly over at least 30 to 60 minutes to minimize the risk of vein irritation and extravasation. Bacteriologic studies to determine the causative organisms and their susceptibility to nafcillin should always be performed. Duration of therapy varies with the type and severity of infection as well as the overall condition of the patient, therefore, it should be determined by the clinical and bacteriological response of the patient. In severe staphylococcal infections, therapy with nafcillin should be continued for at least 14 days. The treatment of endocarditis and osteomyelitis may require a longer duration of therapy.

CONTRAINDICATION A history of a hypersensitivity (anaphylactic) reaction to any penicillin is a contraindication. Solutions containing dextrose may be contraindicated in patients with known allergy to corn or corn products.

Serious and occasionally fatal hypersensitivity (anaphylactic) reactions have been reported in patients receiving beta-lactam antibacterial drugs. These reactions are more likely to occur in individuals with a history of penicillin hypersensitivity and/or a history of sensitivity to multiple allergens. Before initiating therapy with Nafcillin, inquire about previous hypersensitivity reactions to penicillins, cephalosporins, or other allergens. If an allergic reaction occurs, discontinue Nafcillin and institute appropriate therapy. Clostridium difficile associated diarrhea (CDAD) has been reported with use of nearly all antibacterial agents, including Nafcillin Injection, USP, and may range in severity from mild diarrhea to fatal colitis. Treatment with antibacterial agents alters the normal flora of the colon leading to overgrowth of C. difficile.

Body as a Whole The reported incidence of allergic reactions to penicillin ranges from 0.7 to 10 percent. 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 and usually occur after parenteral therapy but have occurred in patients receiving oral therapy.

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.

Store at or below -20°C/-4°F.