348 Absence of Withdrawal Symptoms and Rebound Insomnia Upon Discontinuation of Daridorexant in Patients with Insomnia

Introduction Abrupt discontinuation of sleep medications in patients with insomnia often causes withdrawal symptoms and rebound insomnia. In a Phase 3 program evaluating efficacy and safety of daridorexant on sleep and daytime functioning in patients with insomnia during 3 months of treatment, the risks of withdrawal symptoms and rebound insomnia were evaluated at treatment cessation. Methods In two randomized, double-blind, 3-month trials, adult (18–64 years) and elderly (≥65) patients with insomnia were assigned (1:1:1) to receive oral daridorexant 25mg, 50mg or placebo (Trial-1, NCT03545191) or 10mg, 25mg or placebo (Trial-2, NCT03575104) every evening. Each trial included a 7-day, single-blind, placebo run-out period following double-blind treatment to evaluate withdrawal symptoms and rebound insomnia. Withdrawal effects were assessed by the change in Benzodiazepine Withdrawal Symptom Questionnaire (BWSQ) total score, from last assessment on double-blind treatment to end of placebo run-out, and occurrence of relevant adverse events (AEs). Rebound insomnia was assessed objectively by change in wake-after-sleep-onset (WASO) and latency-to-persistent sleep (LPS), from baseline to first night of placebo run-out, and by subjective total-sleep-time (sTST), from baseline to end of run-out (mean of 7-days). Analyses included all patients who received ≥1 dose of placebo run-out treatment (Trial-1: N=852; Trial-2: N=851). Results No increase in mean BSWQ score from last assessment on double-blind treatment to end of placebo run-out was reported (Trial-1: 25mg, -0.6±2.3; 50mg, -0.6±2.3; placebo, -0.7±2.3; Trial-2: 10mg, -0.5±2.6; 25mg, -0.4±1.9; placebo, -0.4±1.4). No patients had a BWSQ score >20 at end of run-out. No AEs suggestive of withdrawal symptoms were reported. Mean WASO and LPS values (min) decreased from baseline to placebo run-out (WASO Trial-1: 25mg, -8.6±55.5; 50mg, -2.5±52.4; placebo, -20.4±45.8; Trial-2: 10mg, -11.6±58.3; 25mg, -5.1±57.9; placebo, -26.2±53.5; LPS Trial-1: 25mg, -17.2±56.7; 50mg, -15.0±55.8; placebo, -27.8±47.2; Trial-2: 10mg, -17.3±67.2; 25mg, -10.3±67.3; placebo, -18.3±63.8) while sTST values (min) increased (Trial-1: 25mg, 43.3±53.8; 50mg, 42.9±59.6; placebo, 42.3±52.7; Trial-2: 10mg, 43.3±52.9; 25mg, 46.8±55.4; placebo, 42.3±53.8) indicating absence of rebound effects. Conclusion Treatment with daridorexant for up to 3-months was not associated with any evidence of drug withdrawal or rebound insomnia upon abrupt discontinuation, indicating no safety concerns for patients should treatment be stopped. Support (if any) Funded by Idorsia Pharmaceuticals Ltd.

0497 Rebound Insomnia During Discontinuation of Chronic Hypnotic Use

Introduction Rebound insomnia refers to worsened sleep relative to baseline on 1-2 nights after discontinuation of active hypnotic medication. Rebound is typically assessed using a placebo substitution. We assessed rebound in an on-going “blinded” clinical trial in which people with insomnia are instructed to discontinue their study medication (i.e., no-pill) after 6 months of nightly use. Methods DSM-V diagnosed people with insomnia (n=31, 26 females), aged 26-61 yrs, with a polysomnographic sleep efficiency of ≤85%, no other sleep disorders, unstable medical or psychiatric diseases or drug dependency completed the clinical trial. Participants were randomized to zolpidem XR (12.5 mg), eszopiclone (3 mg) or placebo nightly for 6 months (blinded groups A: n=11, B: n=9, C: n=11). After 6 months, over a 2-week choice period, they were given the instruction to discontinue their nightly hypnotic use with an opportunity, if necessary, to self-administer either 1, 2, or 3 capsules of their assigned medication (zolpidem XR 6.25 mg, 6.25 mg, placebo; eszopiclone 2 mg, 1 mg, placebo as capsules 1, 2 and 3 respectively; or 3 placebos). On baseline and the14 discontinuation nights, sleep was recorded and scored by actigraphy for sleep efficiency (SE), sleep latency (LAT) and wake after sleep onset (WASO). Results Relative to the baseline night, on the first discontinuation night there was no difference in SE, LAT, and WASO. Fifteen subjects stopped taking study medication when told to discontinue and 16 subjects took study medication on one night or more. While not differing on baseline or night 1, on night 14 the last study night the medication users had a lower SE (75.9 vs 87.7 %, p<.0.004) and a longer LAT (61.5 vs 14.5 min, p<0.05). Conclusion Difficulty discontinuing hypnotic use is not specifically related to rebound insomnia. We reported in a companion abstract those with insomnia and hyperarousal, defined by MSLT, are those with difficulty discontinuing hypnotic use and as shown here slept poorly on the last study night. Support NIDA, grant#: R01DA038177 awarded to Dr. Roehrs