Propylene Glycol Interference In Gas -

To the Editor: We wish to substantiate the important observations of LeGatt and Tisdell (1) cautioning against the use of propylene glycol as an internal standard for quantifying ethylene glycol. A 32-yearold woman presented to our emergency department in an agitated state after the ingestion of multiple drugs in an attempted suicide. Gastric lavage and charcoal were administered as well as intravenous diazepam (Valium) and borazepam (Ativan) for sedation. While attempting to quantify ethylene glycol in her serum by gas chromatography, we observed that the specimen contained a compound that was eluted with a retention time similar to that of propylene glycol, the internal standard. Although ethylene glycol was undetectable, concentrations of propylene glycol at admission as well as in subsequent serum specimens obtained over the next 35 h were substantial (Table 1). Propylene glycol concentrations peaked 10-15 h after admission to the hospital. Subsequently it was determined that Ativan and Valium contained propylene glycob, 80% and 40%, by weight, respectively. Calculations based on the administered doses of these two benzodiazepines revealed that 18 g of propylene glycol had been given. In addition, lactic acidosis (Table 1) was observed, presumably as a consequence of propylene glycol toxicity (2). Thus, as previously described in another patient for whom measurement of ethylene glycob was requested, we found propylene glycol in serum after treatment with intravenous formulations that contained propylene glycob. Therefore, in measurements of ethylene glycol by gas chromatography, 1,3-propanediob (e.g.) should be used as an internal standard (1) to avoid interference from propylene glycob.