Immediate- and controlled-release zolpidem ingestions reported to Texas poison centers

Zolpidem is available in immediate-release (IR) and controlled-release (CR) formulations. This investigation examined whether there were differences in zolpidem IR and CR ingestions reported to poison control centers. Zolpidem ingestions that did not involve co-ingestants reported to Texas poison control centers during 2005-2008 were identified. The ingestions were grouped by IR and CR formulations and compared with respect to demographic and clinical factors. There were 734 IR and 163 CR ingestions. The mean dose ingested was 92.9 mg and 104.6 mg, respectively. IR and CR cases were, respectively, 56.9% and 58.3% male, 54.6% and 49.7% age >19 years, 65.0% and 65.0% already at or en route to a health care facility when the poison control center was contacted, and 30.1% and 39.3% involved no effect. The most frequently reported adverse clinical effects were, for IR and CR, respectively, drowsiness (54.4% vs 42.3%), tachycardia (10.6% vs 11.7%), ataxia (6.3% vs 11.7%), slurred speech (6.3% vs 6.7%), vomiting (5.0% vs 5.5%) and hallucinations/delusions (4.9% vs 3.1%). The distribution of zolpidem IR and CR ingestions reported to Texas poison control centers were similar. However, zolpidem CR ingestions appeared less likely to result in drowsiness and hallucinations but more likely to result in ataxia.