Nafcillin
chemical compound
Nafcillin sodium is a narrow-spectrum, second-generation beta-lactam antibiotic of the penicillin class. As a beta-lactamase-resistant penicillin, it is used to treat infections caused by Gram-positive bacteria, in particular, species of staphylococci that are resistant to other penicillins.
Nafcillin is considered therapeutically equivalent to oxacillin, although one retrospective study found greater rates of hypokalemia and acute kidney injury in patients taking nafcillin compared to patients taking oxacillin.
Indications
Nafcillin is approved by the FDA for use in treating Staphylococcus infections, including strains resistant to other penicillin-class antibiotics. One notable exception is that Nafcillin is not indicated for treatment of MRSA cases.
U.S. clinical practice guidelines recommend either nafcillin or oxacillin as the first-line treatment of choice for staphylococcal endocarditis in patients without artificial heart valves.
Side-effects
As with all penicillins, serious life-threatening allergic reactions can occur.
Milder side-effects include:
Hypokalemia
Nausea and vomiting
Diarrhea, often due to suppression of normal gastrointestinal bacteria, which, on occasion, leads to a more serious super-infection with an organism like Clostridioides difficile
Abdominal pain
Yeast infections (thrush) affecting the mouth and tongue or vagina
Agranulocytosis, neutropenia
Interactions
There is evidence that nafcillin induces cytochrome P-450 enzymes, specifically CYP2C9. Several drugs with a narrow therapeutic window, such as warfarin and nifedipine, are metabolized by CYP2C9.
Nafcillin contains salts added as stability media.
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