Nafcillin-Associated Hypokalemia

Hypokalemia is a common finding in various clinical settings; it is associated with diuretic use and loss of potassium via the gastrointestinal tract. Less common causes are renal tubular acidosis, diabetic ketoacidosis, excess insulin, primary hyperaldosteronism, and medications, such as amphotericin B. Nafcillin, a narrow-spectrum penicillin class antibiotic, which is selectively prescribed for methicillin-susceptible Staphylococcal aureus infections, and is commonly associated with gastrointestinal side effects, such as nausea, vomiting, and abdominal pain. However, in rare cases it can cause hypokalemia, which is usually overlooked. Severe hypokalemia was detected in a 59-year-old male patient hospitalized due to traumatic cerebral hemorrhage who received 12 g of nafcillin per day for more than 2 weeks for sepsis caused by methicillin-sensitive Staphylococcus epidermidis . We confirmed the association between nafcillin and hypokalemia through further evaluation and a review of the relevant literature. Clinicians should be aware of hypokalemia as a complication when using high doses of nafcillin.