Nafcillin sodium salt monohydrate

Nafcillin sodium salt monohydrate is an antibiotic resistant to beta-lactamase.

Nafcillin sodium, 6-(2-ethoxy-1-naphthyl)penicillin sodium(Unipen), is another semisynthetic penicillin that resultedfrom the search for penicillinase-resistant compounds. Likemethicillin, nafcillin has substituents in positions ortho tothe point of attachment of the aromatic ring to the carboxamidegroup of penicillin. No doubt, the ethoxy group andthe second ring of the naphthalene group play steric roles instabilizing nafcillin against penicillinase. Very similar structureshave been reported to produce similar results in somesubstituted 2-biphenylpenicillins.
Unlike methicillin, nafcillin is stable enough in acid topermit its use by oral administration. When it is givenorally, its absorption is somewhat slow and incomplete,but satisfactory plasma levels may be achieved in about1 hour. Relatively small amounts are excreted throughthe kidneys; most is excreted in the bile. Even thoughsome cyclic reabsorption from the gut may occur, nafcillingiven orally should be readministered every 4 to 6 hours.This salt is readily soluble in water and may be administeredintramuscularly or intravenously to obtain highplasma concentrations quickly for the treatment of seriousinfections.
Nafcillin sodium may be used in infections causedsolely by penicillin G-resistant staphylococci or whenstreptococci are present also. Although it is recommendedthat it be used exclusively for such resistant infections, nafcillin is also effective against pneumococci and groupA -hemolytic streptococci. Because, like other penicillins,it may cause allergic side effects, it should be administeredwith care.