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No evidence of dependence with zolpidem CR during long-term treatment, findings show

Wednesday, December 12 2007 | Comments
Evidence Grade 0 What's This?
Among adults with chronic primary insomnia, long-term, as-needed use of zolpidem extended-release (zolpidem CR) 12.5 mg tablets does not seem to be associated with the development of tolerance or rebound insomnia, study findings demonstrate.

As part of the double-blind study, researchers randomized 1,025 adults aged 18 to 64 years with primary insomnia to take zolpidem CR 12.5 mg or placebo on an as-needed basis (3-7 nights per week) for 6 months. A total of 1,018 participants took >=1 dose of study medication (zolpidem CR, n=669 and placebo, n=349).

Investigators reviewed participant responses to the Patient Global Impression scale (PGI)-Item 4 (medication strength), collected during every fourth week of treatment, and responses to daily morning questionnaires, which provided subjective reports of total sleep time (TST), wake after sleep onset (WASO), number of awakenings (NAW), and sleep-onset latency (SOL).

Of the patients randomized to treatment, 64.7% of the zolpidem group and 52.4% of the placebo group completed the double-blind treatment period. Rates of discontinuation because of lack of efficacy were 4.7% and 23.4%, respectively.

In patient ratings of medication strength and subjective reports of WASO and TST, there was no evidence of loss of a therapeutic effect of zolpidem during the 6 months of treatment. Differences between zolpidem and placebo in questionnaire-reported efficacy variables were statistically significant at every monthly assessment (TST months 1-6, P<.0001; SOL months 1-6, P<=.0014; WASO months 1-6, P<.0001; NAW month 1, P=.0515; months 2-6, P<.0001).

Mean weekly tablet intake was stable throughout the study in both treatment groups (mean tablet intake in the zolpidem group, 4.9-5.2 tablets per week). The authors noted that the proportion of zolpidem-treated patients who took 7 pills per week also remained stable during treatment.

Rebound insomnia, defined as a worsening of mean WASO or TST relative to baseline, was assessed through patient reports for untreated nights (those following 4 nights of treatment) during the double-blind phase and for the first 3 nights of the 7-day runout phase at the end of the study.

Mean WASO for untreated nights was not greater than mean WASO at baseline during any month of the double-blind phase or during the runout phase; mean TST for untreated nights was not less than mean baseline TST during months 2 through 6 of the double-blind phase or during the runout phase (mean TST for untreated nights during month 1 seemed slightly worse than mean baseline TST). (Krystal A, et al. Poster NR585.)

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