» Nafcillin Injection is a sterile isoosmotic solution of Nafcillin Sodium and one or more buffer substances in Water for Injection. It contains dextrose as a tonicity-adjusting agent. It contains an amount of nafcillin sodium equivalent to not less than 90.0 percent and not more than 120.0 percent of the labeled amount of nafcillin (C₂₁H₂₂N₂O₅S). It contains no antimicrobial preservatives.