In a study of five healthy adults administered a single 500 mg dose of nafcillin by intravenous injection over seven minutes, the mean plasma concentration of the drug was approximately 30 mcg/mL at 5 minutes after injection.

Nafcillin is indicated in the treatment of infections caused by penicillinase-producing staphylococci which have demonstrated susceptibility to the drug.

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.

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. Other adverse reactions include Local Reactions, Nervous System reactions, Nephrotoxicity, Hepatic Reactions, Gastrointestinal Reactions, and Metabolic Reactions.

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.

Nafcillin should generally not be administered to patients with a history of sensitivity to any penicillin.