Incidence and Prediction of Rhabdomyolysis Following Doxylamine Overdose

BACKGROUND: Doxylamine, an antihistamine with sleep inducing property, is the most commonly intoxicated drug in the urban ED. This drug is relatively safe but is known to induce rhabdomyolysis in rare occasion. The purpose of this study is to determine the incidence of rhabdomyolysis after doxylamine overdose and prognostic factors that contributes to this complication. METHOD: This study was conducted from 26 patients admitted to our hospital after doxylamine intoxication during the period from April 1999 to June 1999. Using the protocol made beforehand, the amount ingested, past history, laboratory results were recorded. Rhabdomyolysis was defined as serum myoglobin over 300 ng/mL or serum creatine phosphokinase(CK) over 1,000 IU/L. Data were analyzed using SPSS program with t-test, Fisher's exact test and discriminant analysis. RESULTS: The rhabdomyolysis was diagnosed in 57.7% of patients. The amount ingested per body weight, prehospital vomiting and low arterial pCO2 predicted occurrence of rhabdomyolysis. The sensitivity of serum CK and myoglobin were 67% and 80% respectively and specificity was 100% for both. The diagnosis was possible for CK after an average of 14hr 20min time after ingestion and 8hr 12min for myoglobin. CONCLUSION: Rhabdomyolysis is a common complication of doxylamine intoxication and if the amount ingested was more than 1 tablet(25mg) per body weight, the incidence of rhabdomyolysis was higher. So, CK measurement after 14 hour postingestion and myoglobin after 8 hour is recommended to decide whether rhabdomyolysis occur.ope