Study objectives: To assess hypnotic self-administration and likelihood of dose escalation over 12 months of nightly use of zolpidem versus placebo in primary insomniacs.
Design: Randomized, double-blind, placebo-controlled, clinical trial.
Setting: Outpatient with tri-monthly one-week, sleep laboratory assessments.
Participants: Thirty-three primary insomniacs, without psychiatric disorders or drug and alcohol abuse, 32-64 yrs old, 14 men and 19 women.
Interventions: Participants were randomized to take zolpidem 10 mg (n = 17) or placebo (n = 16) nightly for 12 months. In probes during month 1, 4, and 12, after sampling color-coded placebo or zolpidem capsules on 2 nights, color-coded zolpidem or placebo was chosen on 5 consecutive nights and 1, 2, or 3 of the chosen capsules (5 mg each) could be self-administered on a given choice night.
Results: Zolpidem was chosen more nights than placebo (80% of nights) and number of nights zolpidem was chosen did not differ over the 12 months. More zolpidem than placebo capsules were self-administered, and the total number of placebo or zolpidem capsules self-administered did not differ as a function of duration of use. In contrast, the total number of placebo capsules self-administered by the placebo group increased across time. The nightly capsule self-administration on zolpidem nights did not differ from that on placebo nights and neither nightly self-administration rates increased over the 12 months. An average 9.3 mg nightly dose was self-administered.
Conclusions: Zolpidem was preferred to placebo, but its self-administration did not increase with 12 months of use. Chronic hypnotic use by primary insomniacs does not lead to dose escalation.
Trial registration: ClinicalTrials.gov NCT01006525.
Keywords: Primary insomnia; chronic nightly use; self-administration; zolpidem.