Patterns of ecstasy-associated hyponatremia in California

We describe the clinical characteristics of patients with ecstasy- (3,4-methylenedioxymethamphetamine [MDMA]) associated hyponatremia (serum sodium level <130 mmol/L) reported to the California Poison Control System during a 5-year period and determine whether a sex difference exists among patients with ecstasy-associated hyponatremia and hyponatremia-associated adverse outcomes.

We performed a retrospective review of cases involving ecstasy intoxication reported to the California Poison Control System and recorded in its computerized database from January 1, 2000, through October 9, 2005. We excluded cases that did not involve MDMA exposure or in which there were no symptoms or were minimal effects only. Confirmation of exposure to MDMA was based on history of use and, when available, urine toxicology testing results positive for MDMA or amphetamine derivatives. Hyponatremia was defined as a measured serum sodium level less than 130 mmol/L.

A total of 1,436 cases potentially involving ecstasy were reported to the California Poison Control System during the 5-year study period, of which 891 were excluded according to the criteria described above. Of the 545 cases that met inclusion criteria, 296 (54.3%) were women and 249 (45.7%) were men. There were 188 cases (34.5%) with a documented serum sodium level, of which 73 (38.8%) reported hyponatremia (Na <130 mmol/L). Of the 73 subjects with hyponatremia, 55 (75.3%) were women and 18 (24.7%) men; of the 115 nonhyponatremic subjects, 50 (43.5%) were women and 65 (56.5%) were men. Among patients with a documented serum sodium level, female sex was associated with increased odds of hyponatremia (odds ratio [OR] 4.0; 95% confidence interval [CI] 2.1 to 7.6). Among women, those with hyponatremia demonstrated increased odds of coma (OR 3.9; 95% CI 1.2 to 12.9), whereas among men, no increased odds of hyponatremia-associated coma were observed (OR 0.8; 95% CI 0.15 to 4.0).

Female sex was associated with increased odds of hyponatremia and increased odds of hyponatremia-associated coma among persons with ecstasy intoxication and a documented serum sodium level reported to the California Poison Control System from 2000 to 2005. Multiple potential confounders, including spectrum bias, incomplete laboratory data, and individual differences in study subject characteristics, prevent determination of causality about sex differences in the incidence of ecstasy-associated hyponatremia and its complications.