Nafcillin

Nafcillin sodium is a narrow-spectrum 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 its safety profile is somewhat different.

If culture shows Methicillin sensitive Staphylococcus aureus and the patient with brain abscess has not beta lactam allergy, one can change vancomycin to nafcillin.

Nafcillin is indicated in the treatment of staphylococcal infections, except those caused by MRSA.

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.

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 Clostridium difficile

Abdominal pain

Yeast infections (thrush) affecting the mouth and tongue or vagina

Agranulocytosis, neutropenia

There is evidence that it 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. These added salts could cause edema or fluid accumulation. It would be prudent to avoid this medication if there were a concern for a congestive heart failure or kidney disease.