Trimethoprim-sulfamethoxazole (TMP/SMX) therapy may rarely be associated with lactic acidosis.
Patient selection: lactic acidosis in a patient treated with trimethoprim-sulfamethoxazole.
Mechanism of lactic acidosis: propylene glycol used as solvent for the drug.
Risk factors for propylene glycol toxicity:
(1) high doses of trimethoprim-sulfamethoxazole
(2) concurrent therapy with lorazepam, phenytoin or other drug containing propylene glycol
(3) chronic kidney disease or acute renal failure
(4) alcohol abuse
Clinical and laboratory features:
(1) metabolic acidosis with elevated osmolal gap
(2) elevated serum lactic acid concentration
(3) exclusion of other causes of lactic acidosis
(4) reversal on discontinuation of the trimethoprim-sulfamethoxazole
Serum propylene glycol concentrations can be measured.
It can also be informative to calculate the amount of propylene glycol infused based on the trimethoprim-sulfamethoxazole dosing.
