The associative factors of delayed-onset rhabdomyolysis in patients with doxylamine overdose

Objectives: The aim of this study was to investigate the associative factors of rhabdomyolysis in patients with doxylamine overdose who had normal creatine phosphokinase levels at admission. Methods: This study included 169 patients who visited the emergency department of a tertiary teaching hospital after doxylamine overdose between January 1, 1998, and March 31, 2009. Demographic information, clinical variables, and laboratory data were investigated for the associative factors of rhabdomyolysis. Results: Thirty-five (21%) of the 169 patients developed rhabdomyolysis. Patients who developed rhabdomyolysis differed from those who did not in the amount of doxylamine ingested, sex, heart rate, initial value of serum creatinine, and alanine aminotransferase. In the multivariate regression analysis, the only reliable predictors of rhabdomyolysis were the amount of doxylamine ingested (P =.004) and heart rate (P <.001). Conclusion: Observation and laboratory follow-up are required for patients with large reported ingestions or tachycardia on admission, even if their creatine phosphokinase levels were normal.