Rhabdomyolysis in Doxylamine Succinate Overdose

ABSTRACT

BACKGROUND: Doxylamine succinate(DS) is an antihistamine commonly used as an over-the-counter medication to relieve insomnia and frequently involved in overdoses. Its overdoses are dominated by anticholinergic effect. Recently it was revealed that DS had a direct effect on muscle, while its exact mechanism is not clear yet. We evaluated the patients with rhabdomyolysis induced by DS overdose for patients disposition based upon clinical decision, especially by creatinine phosphokinase(CPK). METHODS: We reviewed retrospectively the medical records of patients admitted by DS overdose from Jan. 1998 to Oct. 1999. Seventy and nine cases of DS overdose were evaluated with respect to age and sex distribution, amount ingested, clinical symptomatology, time from ingestion to visit, pattern of CPK, amount of bicarbonate used as therapy, complication and prognosis, especially in patients complicated rhabdomyolysis. RESULTS: Rhabdomyolysis, diagnosed as more than 1,000I. U/L of CPK, has been noted in 25(31.6%) of 79 cases of DS overdose visited to our emergency department(ED). In patients diagnosed rhabdomyolysis, the number of man was 10 cases(40%) and the number aged between 20 and 40 years was 22 cases(88%). The average time from DS ingestion to ED visit was 459 minutes. The amount of DS ingested was 500-5,000mg(mean, 1,980mg). 13(52%) cases ingested less than 2,250mg of DS. The initial levels of CPK(range, 48-14900I. U/L; normal range, 26-200I. U/L) after admitting to our emergency department were normal in 15 cases(60%) of rhabdomyolysis patients. The range of peak CPK levels after ingestion was 607 to 412,500I. U/L(mean, 33,550I. U/L). Its peak time was 6 to 96 hours(mean, 28.96 hours). In 14 cases(67%) of 21 visiting within 24 hours after ingestion, peak time of CPK ranged 12 to 24 hours after ingestion. The amount of bicarbonate used as therapy of rhabdomyolysis ranged 100 to 2,740mEq(mean, 656mEq) and all patients was discharged after improvement without other complication including acute renal failure. CONCLUSIONS : Although patients ingested less than 2,250mg of DS, emergency physicians should observe them more than 24 hours after DS ingestion with CPK follow-up after gastric irrigation and charcoal administration.