The antimicrobial trimethoprim is structurally related to potassium-sparing diuretics and may consequently lead to derangements in electrolyte and acid-base balance. Since no report so far analyzed the literature documenting individual cases with electrolyte and acid-base derangements induced by trimethoprim, a systematic review was carried out.
We retained 53 reports documenting 68 cases (42 males and 26 females 23 to 96 years of age) of electrolyte or acid-base derangements occurring on trimethoprim for about 5 days.
One hundred five electrolyte imbalances were detected in the 68 patients: hyperkalemia (>5.0 mmol/L) in 62 (91%), hyponatremia (<135 mmol/L) in 29 (43%) and metabolic acidosis (pH<7.38 and bicarbonate <19 mmol/L) in 14 (21%) cases. Following possible predisposing factors for electrolyte and acid-base abnormalities were found in 54 (79%) patients: high-dose trimethoprim, comedication with drugs that have been associated with electrolyte and acid-base derangements, preexisting kidney disease, age ≥80 years and diabetes mellitus.
High-dose trimethoprim, comedicated with drugs that have been associated with electrolyte and acid-base derangements, poor kidney function, age ≥80 years and diabetes mellitus predispose to trimethoprim-associated electrolyte and acid-base abnormalities. Clinicians must recognize patients at risk, possibly avoid drug combinations that may worsen the problem and monitor the laboratory values.