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Mechanism of Action
Zolpidem, the active moiety of zolpidem tartrate, is a hypnotic agent with a chemical structure unrelated to benzodiazepines, barbiturates, or other drugs with known hypnotic properties. It interacts with a GABA-BZ complex and shares some of the pharmacological properties of the benzodiazepines. In contrast to the benzodiazepines, which nonselectively bind to and activate all BZ receptor subtypes, zolpidem in vitro binds the BZ1 receptor preferentially with a high affinity ratio of the alphai/alphas subunits. This selective binding of zolpidem on the BZ1 receptor is not absolute, but it may explain the relative absence of myorelaxant and anticonvulsant effects in animal studies as well as the preservation of deep sleep (stages 3 and 4) in human studies of zolpidem at hypnotic doses.
Intermezzo disintegrates in the sublingual cavity after administration. On average, Intermezzo is rapidly absorbed in both genders, with a mean T^ across studies of about 35 minutes to about 75 minutes.
In healthy normal volunteers (age 21 to 45 years) dosed with 3.5 mg Intermezzo, the average Cmax and AUC were 77 ng/mL and 296 ng-h/mL, respectively in women. The average Cmax and AUC were 53 ng/mL and 198 ng-h/mL, respectively in men. In women, the average Cmax and AUC of the 1.75 mg Intermezzo dose were 37 ng/mL and 151 ng-h/mL, respectively.
Food decreased the overall Cmax and AUC of Intermezzo 3.5 mg by 42% and 19%, respectively, and increased the time to peak exposure (Tmax) to nearly 3 hours. For optimal effect, Intermezzo should not be administered with or immediately after a meal.
Based on data obtained with oral zolpidem, the total protein binding was found to be 93% ±0.1% and remained constant independent of concentration between 40 ng/mL and 790 ng/mL.
Based on data obtained with oral zolpidem, zolpidem tartrate is converted to inactive metabolites that are eliminated primarily by renal excretion.
The elimination half-life of a single dose of a 3.5 mg Intermezzo sublingual tablet is approximately 2.5 hours (range 1.4 to 3.6 hours).
Elderly: The recommended dose for Intermezzo is 1.75 mg. A pharmacokinetic study of 1.75 mg and 3.5 mg doses of Intermezzo showed that the plasma Cmax and AUC0-4hr in elderly subjects following the 3.5 mg dose was higher by 34% and 30%, respectively, than the non-elderly subjects. The Cmax and AUC of 1.75 mg in elderly subjects were consistently lower than those observed for the 3.5 mg dose in non-elderly subjects but consistently higher than the 1.75 mg dose in non-elderly subjects. The elimination half-life remained unchanged.
Hepatic Impairment: The pharmacokinetics of oral zolpidem tartrate in eight patients with chronic hepatic insufficiency were compared to results in subjects with normal hepatic function. Following a single 20 mg oral zolpidem tartrate dose, mean Cmax and AUC were found to be two times (250 ng/mL vs. 499 ng/mL) and five times (788 ng-hr/mL vs. 4203 ng-hr/mL) higher, respectively, in hepatically compromised patients compared to subjects with normal hepatic function. Tmax did not change. The mean half-life in cirrhotic patients of 9.9 hr (range: 4.1 to 25.8 hr) was greater than that observed in subjects with normal hepatic function of 2.2 hr (range: 1.6 to 2.4 hr). Dosing should be modified accordingly in patients with hepatic insufficiency [see DOSAGE AND ADMINISTRATION].
Renal Impairment: The pharmacokinetics of zolpidem tartrate were studied in 11 patients with end-stage renal failure (mean ClCr-= 6.5 ± 1.5 mL/min) undergoing hemodialysis three times a week, who were dosed with zolpidem tartrate 10 mg orally each day for 14 or 21 days. No statistically significant differences were observed for Cmax, Tmax, half-life, and AUC between the first and last day of drug administration when baseline concentration adjustments were made. Zolpidem was not hemodialyzable. No accumulation of unchanged drug appeared after 14 or 21 days. Zolpidem pharmacokinetics were not significantly different in renally-impaired patients. No dosage adjustment is necessary in patients with renal impairment.
Co-administration of zolpidem with other CNS depressants increases the risk of CNS depression [see WARNINGS AND PRECAUTIONS]. Zolpidem tartrate was evaluated in healthy volunteers in single-dose interaction studies for several CNS drugs. Imipramine in combination with zolpidem produced no pharmacokinetic interaction other than a 20% decrease in peak levels of imipramine, but there was an additive effect of decreased alertness. Similarly, chlorpromazine in combination with zolpidem produced no pharmacokinetic interaction, but there was an additive effect of decreased alertness and psychomotor performance.
A study involving haloperidol and zolpidem revealed no effect of haloperidol on the pharmacokinetics or pharmacodynamics of zolpidem. The lack of a drug interaction following single-dose administration does not predict the absence of an effect following chronic administration.
Following five consecutive nightly doses at bedtime of oral zolpidem tartrate 10 mg in the presence of sertraline 50 mg (17 consecutive daily doses, at 7:00 am, in healthy female volunteers), zolpidem Cmax was significantly higher (43%) and Tmax was significantly decreased (-53%). Pharmacokinetics of sertraline and N-desmethylsertraline were unaffected by zolpidem.
A single-dose interaction study with zolpidem tartrate 10 mg and fluoxetine 20 mg at steady-state levels in male volunteers did not demonstrate any clinically significant pharmacokinetic or pharmacodynamic interactions. When multiple doses of zolpidem and fluoxetine were given at steady state and the concentrations evaluated in healthy females, an increase in the zolpidem half-life (17%) was observed. There was no evidence of an additive effect in psychomotor performance.
Drugs that Affect Drug Metabolism via Cytochrome P450
Some compounds known to inhibit CYP3A may increase exposure to zolpidem. The effect of inhibitors of other P450 enzymes on the pharmacokinetics of zolpidem is unknown.
A single-dose interaction study with zolpidem tartrate 10 mg and itraconazole 200 mg at steady-state levels in male volunteers resulted in a 34% increase in AUC0-∞of zolpidem tartrate. There were no pharmacodynamic effects of zolpidem detected on subjective drowsiness, postural sway, or psychomotor performance.
A single-dose interaction study with zolpidem tartrate 10 mg and rifampin 600 mg at steady-state levels in female subjects showed significant reductions of the AUC (-73%), Cmax, (-58%), and T½ (-36 %) of zolpidem together with significant reductions in the pharmacodynamic effects of zolpidem tartrate. Rifampin, a CYP3 A4 inducer, significantly reduced the exposure to and the pharmacodynamic effects of zolpidem.
A single-dose interaction study with zolpidem tartrate 5 mg and ketoconazole, a potent CYP3 A4 inhibitor, given as 200 mg twice daily for 2 days increased Cmax of zolpidem (30%) and the total AUC of zolpidem (70%) compared to zolpidem alone and prolonged the elimination half-life (30 %) along with an increase in the pharmacodynamic effects of zolpidem. Consideration should be given to using a lower dose of zolpidem when ketoconazole and zolpidem are given together.
Other Drugs with No Interactions with Zolpidem
A study involving cimetidine/zolpidem tartrate and ranitidine/zolpidem tartrate combinations revealed no effect of either drug on the pharmacokinetics or pharmacodynamics of zolpidem.
Zolpidem tartrate had no effect on digoxin pharmacokinetics and did not affect prothrombin time when given with warfarin in healthy subjects.
Middle-of-the-Night Awakening Trials
Intermezzo was evaluated in two randomized, double-blind, placebo-controlled studies (Studies 1 and 2) in patients with insomnia characterized by difficulty returning to sleep after a middle-of-the-night (MOTN) awakening. In these studies, patients met the diagnosis for primary insomnia as defined by the Diagnostic and Statistical Manual of Mental Disorders (DSM-FV-TR) and had at least three prolonged MOTN awakenings per week that were at least 30 minutes in duration.
Sleep Laboratory Study (Scheduled Dosing)
Adult patients aged 19 to 64 years (N=82; 58 female, 24 male) with a history of difficulty returning to sleep after middle-of-the-night awakenings were evaluated in a double-blind, placebo-controlled, 3-period cross-over sleep laboratory study (Study 1). The primary outcome measure was latency to persistent sleep (LPS).
Doses of 3.5 mg and 1.75 mg of Intermezzo significantly decreased both objective (by polysomnography) and subjective (patient-estimated) sleep latency after a scheduled middle-of-the-night awakening as compared to placebo. The effect on sleep latency was similar for females receiving 1.75 mg of Intermezzo and males receiving 3.5 mg of Intermezzo.
Outpatient Study (As-needed Dosing)
Adult patients aged 18 to 64 years (N=295; 201 women, 94 men) with difficulty returning to sleep after middle-of-the-night awakenings were evaluated in a double-blind, placebo-controlled 4-week outpatient study of Intermezzo. Patients took study drug (3.5 mg of Intermezzo or placebo) on an as needed (prn) basis, when they had difficulty returning to sleep after waking in the middle of the night, provided they had at least 4 hours time remaining in bed. Subjective (patient-estimated) time to fall back to sleep after middle-of-the-night awakening was significantly shorter for Intermezzo 3.5 mg compared to placebo.
Special Safety Studies
A randomized, double-blind, placebo-controlled, active-control, single-center, four-period, crossover study in 40 healthy subjects was conducted to evaluate the effects of middle-of-the-night administration of Intermezzo on next-morning driving performance. The four randomized treatments included Intermezzo 3.5 mg four hours before driving,
Intermezzo 3.5 mg three hours before driving, placebo, and a positive control (an unapproved sedative-hypnotic) given nine hours before driving.
The primary outcome measure was the change in the standard deviation of lateral position (SDLP), a measure of driving impairment. The results were analyzed using a symmetry analysis, which determined the proportion of subjects whose change from their own SDLP in the placebo condition was statistically significantly above a threshold thought to reflect clinically meaningful driving impairment.
When driving began 3 hours after taking Intermezzo, testing had to be terminated for one subject (a 23-year old woman) due to somnolence. Overall, the symmetry analysis showed a statistically significant impairing effect at 3 hours. When driving began 4 hours after taking Intermezzo, statistically significant impairment was not found, but numerically Intermezzo was worse than placebo. Zolpidem blood levels were not measured in the driving study, and the study was not designed to correlate specific blood level with degree of impairment. However, the estimated blood level of zolpidem in patients whose SDLP worsened according to the symmetry analysis is considered to present a risk for driving impairment. In some women, the 3.5 mg dose of Intermezzo results in zolpidem blood levels that remain at or sometimes considerably above this level 4 or more hours after dosing. Therefore, the recommended dose for women is 1.75 mg. A small negative effect on SDLP may remain in some patients 4 hours after the 1.75 mg dose in women, and after the 3.5 mg dose in men, such that a potential negative effect on driving cannot be completely excluded.
In studies performed with other zolpidem formulations (5 mg to 10 mg oral zolpidem tartrate) given at bedtime, there was no objective (polysomnographic) evidence of rebound insomnia at recommended doses seen in studies evaluating sleep on the nights following discontinuation. There was subjective evidence of impaired sleep in the elderly on the first post-treatment night at doses above the recommended elderly dose of 5 mg oral zolpidem tartrate.
Memory impairment in controlled studies
Controlled studies in adults utilizing objective measures of memory yielded no consistent evidence of next-day memory impairment following the administration at bedtime of 5 mg to 10 mg oral zolpidem tartrate. However, in one study involving zolpidem tartrate doses of 10 mg and 20 mg, there was a significant decrease in next-morning recall of information presented to subjects during peak drug effect (90 minutes post-dose), i.e., these subjects experienced anterograde amnesia. There was also subjective evidence from adverse event data for anterograde amnesia occurring in association with the administration of oral zolpidem tartrate, predominantly at doses above 10 mg.
Last reviewed on RxList: 12/5/2011
This monograph has been modified to include the generic and brand name in many instances.
Additional Intermezzo Information
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