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 (see CLINICAL PHARMACOLOGY – Susceptibility Test Methods ). 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 sp., therapy with Nafcillin for Injection should be discontinued and alternative therapy provided. …

• Nafcillin for Injection is available for intramuscular and intravenous use
• The usual intravenous dosage for adults is 500 mg every 4 hours
• For severe infections, 1 gram every 4 hours is recommended
• Administer slowly over at least 30 to 60 minutes to minimize the risk of vein irritation and extravasation
• RECOMMENDED DOSAGE FOR NAFCILLIN FOR INJECTION, USP Drug
• Adults
• Infants and Children < 40 kg (88 lbs) Other Recommendations Nafcillin 500 mg IM every 4 to 6 hours
• IV every 4 hours 25 mg/kg IM twice daily
• Neonates 10 mg/kg IM twice daily 1 gram IM or IV every 4 hours (severe infections) 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
• No dosage alterations are necessary for patients with renal dysfunction, including those on hemodialysis
• Hemodialysis does not accelerate nafcillin clearance from the blood

• 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
• Safety and effectiveness
• In pediatric patients have been established for the use of intramuscular nafcillin

Clinical studies of nafcillin for injection 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. …

• Patients should be counseled that antibacterial drugs including nafcillin for injection should only be used to treat bacterial infections
• They do not treat viral infections (e.g., the common cold)
• When nafcillin for injection is prescribed to treat a bacterial infection, patients should be told that although it is common to feel better early in the course of therapy, the medication should be taken exactly as directed. …

A history of a hypersensitivity (anaphylactic) reaction to any penicillin is a contraindication.

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. …

SERIOUS AND OCCASIONALLY FATAL HYPERSENSITIVITY (ANAPHYLACTIC) REACTIONS HAVE BEEN REPORTED IN PATIENTS ON PENICILLIN THERAPY. 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, CAREFUL INQUIRY SHOULD BE MADE CONCERNING PREVIOUS HYPERSENSITIVITY REACTIONS TO PENICILLINS, CEPHALOSPORINS, OR OTHER ALLERGENS. IF AN ALLERGIC REACTION OCCURS, NAFCILLIN SHOULD BE DISCONTINUED AND APPROPRIATE THERAPY INSTITUTED. …

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. …

Pregnancy Teratogenic Effects 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. …

Neurotoxic reactions similar to those observed with penicillin G may arise with intravenous doses of nafcillin especially in patients with concomitant hepatic insufficiency and renal dysfunction (see PRECAUTIONS ). In the case of overdosage, discontinue nafcillin, treat symptomatically and institute supportive measures as required. Hemodialysis does not increase the rate of clearance of nafcillin from the blood.

Take it when you remember, unless it is nearly time for the next dose. Then skip the missed one. Never take two doses at once to make up for it. Check your leaflet, as some medicines are different.