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Suvorexant

Phase 3

Delirium | Small molecule | Psychiatry |Merck & Company, Inc.|Last Updated: Aug 28, 2026

Target and mechanism

Molecular targetHCRTR2, HCRTR1
Target classAntagonist
ModalitySmall molecule

Success Probability

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Market & Valuation

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Trial Design

RandomizedDouble-BlindPLACEBO_CONTROLLED
Total Trials1
Total Enrollment207

FDA Designations

No designations recorded

Clinical trial landscape

Suvorexant · 13 trials · 9 indications

Phase 3 6Phase 2 3Phase 1 4
NCT06655883A Study of Suvorexant (MK-4305) for the Treatment of Insomnia Disorder in Participants With Opioid Use Disorder (MK-4305-098)Insomnia
RECRUITING300 Analytics
NCT04571944Efficacy and Safety of Suvorexant (MK-4305) for Reducing Incidence of Delirium in Japanese Participants at High Risk of Delirium (MK-4305-085)Delirium
COMPLETED207 Analytics
NCT02750306Safety and Efficacy of Suvorexant (MK-4305) for the Treatment of Insomnia in Participants With Alzheimer's Disease (MK-4305-061)Sleep Initiation and Maintenance Disorders
COMPLETED285 Analytics
NCT01097616Safety and Efficacy Study of Suvorexant in Participants With Primary Insomnia - Study A (MK-4305-028)Primary Insomnia
COMPLETED1,023 Analytics
NCT01097629Safety and Efficacy Study of Suvorexant in Participants With Primary Insomnia - Study B (MK-4305-029)Primary Insomnia
COMPLETED1,020 Analytics
NCT01021813A Long Term Safety Study of Suvorexant in Participants With Primary Insomnia (MK-4305-009 AM3)Insomnia
COMPLETED781 Analytics
PHASE3RECRUITING
A Study of Suvorexant (MK-4305) for the Treatment of Insomnia Disorder in Participants With Opioid Use Disorder (MK-4305-098)
InsomniaUnlock trial analytics
PHASE3COMPLETED
Efficacy and Safety of Suvorexant (MK-4305) for Reducing Incidence of Delirium in Japanese Participants at High Risk of Delirium (MK-4305-085)
DeliriumUnlock trial analytics
PHASE3COMPLETED
Safety and Efficacy of Suvorexant (MK-4305) for the Treatment of Insomnia in Participants With Alzheimer's Disease (MK-4305-061)
Sleep Initiation and Maintenance DisordersUnlock trial analytics
PHASE3COMPLETED
Safety and Efficacy Study of Suvorexant in Participants With Primary Insomnia - Study A (MK-4305-028)
Primary InsomniaUnlock trial analytics
PHASE3COMPLETED
Safety and Efficacy Study of Suvorexant in Participants With Primary Insomnia - Study B (MK-4305-029)
Primary InsomniaUnlock trial analytics
PHASE3COMPLETED
A Long Term Safety Study of Suvorexant in Participants With Primary Insomnia (MK-4305-009 AM3)
InsomniaUnlock trial analytics

Study Endpoints

Primary Endpoints

Change from Baseline in Total Sleep Time at Week 8
Baseline and Week 8

Total sleep time will be measured in a sleep laboratory by polysomnography at the participant's habitual bedtime. Change from baseline in total sleep time at Week 8 will be reported.

Number of Participants Who Experience One or More Adverse Events (AEs)
Up to approximately 10 weeks

An AE is any untoward medical occurrence in a clinical study participant, temporally associated with the use of study intervention, whether or not considered related to the study intervention.

Number of Participants Who Experience One or More Serious Adverse Events (SAEs)
Up to approximately 10 weeks

An SAE is any untoward medical occurrence that at any dose results in death, is life threatening, requires or prolongs inpatient hospitalization, results in persistent or significant disability or incapacity, is a congenital anomaly or birth defect or is another important medical event deemed such by medical or scientific judgement.

Number of Participants Who Discontinue Study Treatment Due to an AE
Up to approximately 8 weeks

An AE is any untoward medical occurrence in a clinical study participant, temporally associated with the use of study intervention, whether or not considered related to the study intervention.

Percentage of Participants With Delirium as Assessed by Diagnostic and Statistical Manual of Mental Disorders, 5th Edition (DSM-5) Criteria
Up to ~8 days

The DSM-5 is the gold standard for the diagnosis of delirium. DSM-5 criteria were used for clinician assessment of delirium. The percentage of participants with delirium per DSM-5 criteria is presented.

Number of Participants Who Experienced One or More Adverse Events (AEs)
Up to ~21 days

An AE is any untoward medical occurrence in a clinical study participant, temporally associated with the use of study intervention, whether or not considered related to the study intervention. The number of participants who experienced one or more AEs is presented.

Number of Participants Who Discontinued Study Treatment Due to an AE
Up to ~7 days

An AE is any untoward medical occurrence in a clinical study participant, temporally associated with the use of study intervention, whether or not considered related to the study intervention. The number of participants who discontinued study treatment due to an AE is presented.

Change From Baseline in Polysomnography-derived Total Sleep Time (TST) at Week 4
Baseline and Week 4

TST was measured at Baseline and at Week 4 in a sleep laboratory by polysomnography, during an 8-hour recording period beginning at participants' habitual bedtime.

Percentage of Participants Who Experienced One or More Adverse Events
Up to 6 weeks

An adverse event (AE) is any untoward medical occurrence in a study participant administered a pharmaceutical product that does not necessarily have to have a causal relationship with this treatment. An AE can therefore be any unfavorable and unintended sign, symptom, or disease temporally associated with the use of a medicinal product, whether or not related to the medicinal product.

Percentage of Participants Who Discontinued Study Drug Due to an Adverse Event
Up to 4 weeks

An adverse event (AE) is any untoward medical occurrence in a study participant administered a pharmaceutical product that does not necessarily have to have a causal relationship with this treatment. An AE can therefore be any unfavorable and unintended sign, symptom, or disease temporally associated with the use of a medicinal product, whether or not related to the medicinal product.

Suvorexant HD Versus Placebo: Change From Baseline in Mean Subjective Total Sleep Time (sTSTm) at Month 1
Baseline and Month 1

sTSTm is the average over a defined day range of the participant's report of the total amount of time spent asleep before waking for the day, as recorded in a daily electronic diary (e-diary). Averages were derived by taking the mean of all available daily measurements (excluding the mornings following any polysomnography \[PSG\] nights) falling within the day range; Month 1 range is Days 23-30 (Day 1 is day of first double-blind dose). A participant must have at least 3 days of data during the defined day range to calculate an average for the day range; otherwise, the mean value was considered missing for that day range. The baseline value is the mean of the last 7 daily measurements obtained during the placebo Run-in period.

Suvorexant HD Versus Placebo: Change From Baseline in sTSTm at Month 3
Baseline and Month 3

sTSTm is the average over a defined day range of the participant's report of the total amount of time spent asleep before waking for the day, as recorded in a daily e-diary. Averages were derived by taking the mean of all available daily measurements (excluding the mornings following any PSG nights) falling within the day range; Month 3 range is Days 76-90 (Day 1 is day of first double-blind dose). A participant must have at least 3 days of data during the defined day range to calculate an average for the day range; otherwise, the mean value was considered missing for that day range. The baseline value is the mean of the last 7 daily measurements obtained during the placebo Run-in period.

Suvorexant HD Versus Placebo: Change From Baseline in Wakefulness After Persistent Sleep Onset (WASO) at Month 1
Baseline and Month 1

WASO is measured during overnight sleep laboratory (PSG) assessments at baseline, Night 1, Month 1 and Month 3, and is defined as the duration of wakefulness from the onset of persistent sleep (i.e., 10 consecutive minutes of sleep) to the end of PSG assessment the following morning. Beginning of PSG assessment ("Lights-Off") is at approximately the participant's habitual bedtime. The participant is awakened, or allowed to get out of bed if already awake, after 8 hours of PSG recording ("Lights-On"). PSG assessments consist of electronic measurement of brain activity and eye and muscle movements. PSG data was scored by a Centralized PSG reading center.

Suvorexant HD Versus Placebo: Change From Baseline in WASO at Month 3
Baseline and Month 3

WASO is measured during overnight sleep laboratory (PSG) assessments at baseline, Night 1, Month 1 and Month 3, and is defined as the duration of wakefulness from the onset of persistent sleep (i.e., 10 consecutive minutes of sleep) to the end of PSG assessment the following morning. Beginning of PSG assessment ("Lights-Off") is at approximately the participant's habitual bedtime. The participant is awakened, or allowed to get out of bed if already awake, after 8 hours of PSG recording ("Lights-On"). PSG assessments consist of electronic measurement of brain activity and eye and muscle movements. PSG data was scored by a Centralized PSG reading center.

Suvorexant HD Versus Placebo: Change From Baseline in Mean Subjective Time to Sleep Onset (sTSOm) at Month 1
Baseline and Month 1

sTSOm is the average over a defined day range of the participant's report of the duration of time that it took to fall asleep, as recorded in a daily e-diary. Averages were derived by taking the mean of all available daily measurements (excluding the mornings following any PSG nights) falling within the day range; Month 1 range is Days 23-30 (Day 1 is day of first double-blind dose). A participant must have at least 3 days of data during the defined day range to calculate an average for the day range; otherwise, the mean value was considered missing for that day range. The baseline value is the mean of the last 7 daily measurements obtained during the placebo Run-in period.

Suvorexant HD Versus Placebo: Change From Baseline in sTSOm at Month 3
Baseline and Month 3

sTSOm is the average over a defined day range of the participant's report of the duration of time that it took to fall asleep, as recorded in a daily e-diary. Averages were derived by taking the mean of all available daily measurements (excluding the mornings following any PSG nights) falling within the day range; Month 3 range is Days 76-90 (Day 1 is day of first double-blind dose). A participant must have at least 3 days of data during the defined day range to calculate an average for the day range; otherwise, the mean value was considered missing for that day range. The baseline value is the mean of the last 7 daily measurements obtained during the placebo Run-in period.

Suvorexant HD Versus Placebo: Change From Baseline in Latency to Onset of Persistent Sleep (LPS) at Month 1
Baseline and Month 1

LPS is measured during overnight sleep laboratory (PSG) assessments at baseline, Night 1, Month 1 and Month 3, and is defined as the duration of time from the beginning of PSG assessment ("Lights-Off") to the first interval of 10 consecutive minutes of sleep. Beginning of PSG assessment ("Lights-Off") is at approximately the participant's habitual bedtime. The participant is awakened, or allowed to get out of bed if already awake, after 8 hours of PSG recording ("Lights-On"). PSG assessments consist of electronic measurement of brain activity and eye and muscle movements. PSG data was scored by a Centralized PSG reading center.

Suvorexant HD Versus Placebo: Change From Baseline in LPS at Month 3
Baseline and Month 3

LPS is measured during overnight sleep laboratory (PSG) assessments at baseline, Night 1, Month 1 and Month 3, and is defined as the duration of time from the beginning of PSG assessment ("Lights-Off") to the first interval of 10 consecutive minutes of sleep. Beginning of PSG assessment ("Lights-Off") is at approximately the participant's habitual bedtime. The participant is awakened, or allowed to get out of bed if already awake, after 8 hours of PSG recording ("Lights-On"). PSG assessments consist of electronic measurement of brain activity and eye and muscle movements. PSG data was scored by a Centralized PSG reading center.

Number of Participants With an Adverse Event (AE) During Initial 3-Month DB TRT Phase
Up to 3 months

An AE is any unfavorable and unintended change in the structure, function or chemistry of the body temporally associated with study drug administration, whether or not considered related to the study drug. Participants with an AE occurring during the initial 3-month DB TRT Phase are counted once in this summary.

Number of Participants Who Discontinued Study Drug Due to an AE Occurring During Initial 3-Month DB TRT Phase
Up to 3 months

An AE is any unfavorable and unintended change in the structure, function or chemistry of the body temporally associated with study drug administration, whether or not considered related to the study drug. Participants who discontinued study drug treatment due to an AE occurring during the initial 3-month DB TRT Phase are counted once in this summary.

Number of Participants With an Adverse Event (AE) During 3-Month DB TRT Phase
Up to 3 months

An AE is any unfavorable and unintended change in the structure, function or chemistry of the body temporally associated with study drug administration, whether or not considered related to the study drug. Participants with an AE occurring during the 3-month DB TRT Phase are counted once in this summary.

Number of Participants Who Discontinued Study Drug Due to an AE Occurring During 3-Month DB TRT Phase
Up to 3 months

An AE is any unfavorable and unintended change in the structure, function or chemistry of the body temporally associated with study drug administration, whether or not considered related to the study drug. Participants who discontinued study drug treatment due to an AE occurring during the 3-month DB TRT Phase are counted once in this summary.

Percentage of Participants Who Experienced Cataplexy Adverse Events (AEs) During the Double-Blind (DB) Treatment Phase
From the first day of study treatment up to 12 months

Cataplexy is defined as a sudden loss of muscle tone while awake which prevents voluntary movement.

Percentage of Participants Who Experienced Sleep Paralysis AEs During the DB Treatment Phase
From the first day of study treatment up to 12 months

Sleep paralysis was defined as the inability to perform voluntary muscle movements during sleep. Sleep paralysis adverse events included sleep-onset paralysis (paralysis as one is falling asleep).

Percentage of Participants Who Experienced Complex Sleep-related Behaviors AEs During the DB Treatment Phase
From the first day of study treatment up to 12 months

Complex sleep-related behaviors were reported as ECIs and were characterized by patients engaging in specific activities while asleep (e.g., eating, drinking, preparing meals, making phone calls, having sex, driving, and sleep walking).

Percentage of Participants Who Experienced Falls AEs During the DB Treatment Phase
From the first day of study treatment up to 12 months

Falls were adjudicated (to establish whether a fall event was due to cataplexy).

Percentage of Participants Who Experienced Suicidal Ideation and/or Behavior AEs During the DB Treatment Phase
From the first day of study treatment up to 12 months

Suicidal ideation included suicidal plans, suicidal tendency, death wishes, life weariness, and suicidal intention. Suicidal behaviors included suicide attempts, suicide gesture, and self-injurious behaviour. Suicidal ideation and/or behavior was reported as an AE and considered an ECI.

Percentage of Participants Who Experienced Hypnagogic/Hypnopompic Hallucinations AEs During the DB Treatment Phase
From the first day of study treatment up to 12 months

Perceptual distortions associated with transitions between wakefulness and sleep were termed as hypnagogic (occurring during the onset of sleep) or hypnopompic (occurring during onset of wakefulness) hallucinations.

Percentage of Participants Who Experienced Selected AEs Associated With Potential for Abuse During the DB Treatment Phase
From the first day of study treatment up to 12 months

The pre-specified terms which were suggestive of abuse potential on this study included depersonalization (feeling of watching oneself act, while having no control over a situation), derealization (alteration in the perception or experience of the external world so that it seems unreal), dissociation (includes a wide array of experiences from mild detachment from immediate surroundings to more severe detachment from physical and emotional experience), euphoric mood (exaggerated feeling of physical and emotional well-being and optimism not consonant with apparent stimuli or events), mania (state of abnormally elevated or irritable mood, arousal, and/or energy levels), hallucination (perception in the absence of a stimulus which has qualities of real perception), and potential study medication misuse.

Total Sleep Time (TST) on the First Postoperative Night
The first postoperative night that the participants received study drug (D0)

Total sleep time (TST) on first postoperative night that patient received study drug, as measured by electroencephalography (EEG). Total sleep time includes amount of time in sleep during the lights out period (defined between 21:00 and 06:00).

Change from baseline in Amyloid-β accumulation measured by plasma pT217/T217 in participants treated with 20 mg suvorexant compared to placebo
18-24 months

Blood collection

LS Mean Sleep Efficiency (SE) During Periods 1 and 2
Night 1 and end of Week 4

SE was defined as total sleep time (TST) in minutes divided by time in bed (measured from lights off to lights on; fixed at 8 hours on each Polysomnography \[PSG\] night) in minutes, multiplied by 100, where TST is defined as the total time (minutes) in Stages 1, 2, 3, 4 and Rapid Eye Movement (REM). SE= (total sleep time/time in bed) x 100

Mean Arterial Oxygen Saturation (SaO2) During Total Sleep Time
Day 4 of each period

Evaluation of the effect of multiple dose suvorexant (MK-4305) on SaO2 during total sleep time as measured by pulse oximetry. Lower SaO2 values are associated with sleep impairment. Total sleep time is the total of all rapid eye movement (REM) and non-REM sleep in a sleep episode.

Number of Participants With Adverse Events
Up to 14 days after last dose

An adverse event (AE) is any unfavorable and unintended change in the structure, function or chemistry of the body temporally associated with study drug administration whether or not considered related to the use of the product.

Number of Participants Discontinued From Study Drug Due to an AE
Up to 15 days

An AE is any unfavorable and unintended change in the structure, function or chemistry of the body temporally associated with study drug administration whether or not considered related to the use of the product.

Mean Apnea-Hypopnea Index (AHI)
Day 4

Evaluation of the effect of multiple dose administration of suvorexant on AHI as measured by polysomnography. The AHI is an overall index of obstructive sleep apnea (OSA) severity. The AHI is calculated by dividing the number of apneas and hypopneas by the number of hours of sleep. AHI values are categorized as mild OSA = 5 to \<15/hr and moderate OSA = 15 to \<30/hr.

Number of Participants With an Adverse Event
Up to 14 days after last dose

An adverse event (AE) is any unfavorable and unintended change in the structure, function or chemistry of the body temporally associated with study drug administration whether or not considered related to the use of the product.

Number of Participants Who Discontinued Study Drug Due to an AE
Up to 13 days

An AE is any unfavorable and unintended change in the structure, function or chemistry of the body temporally associated with study drug administration whether or not considered related to the use of the product.

Area Under the Plasma Concentration Versus Time Curve (AUC) From Time Zero to Infinity (0-∞) After Single Dose Suvorexant: Severe Renal Impairment Participants Versus Healthy Participants (Part I)
Predose and 0.5, 1, 2, 4, 6, 9, 12, 16, 24, 48, 72, 96, and 120 hours post-dose

Overall exposure was assessed by the area under the plasma concentration versus time curve from time zero to infinity (AUC\[0-∞\]). AUC(0-∞) was calculated as the sum of the AUC to the last time point with a detectable plasma concentration (AUC\[0-last\]) and the extrapolated area given by the quotient of the last detectable concentration and the apparent terminal rate constant (λ).

AUC(0-∞) After Single Dose Suvorexant: Moderate and Mild Renal Impairment Participants Versus Healthy Participants (Part II)
Predose and 0.5, 1, 2, 4, 6, 9, 12, 16, 24, 48, 72, 96, and 120 hours post-dose

Overall exposure was assessed by the area under the plasma concentration versus time curve from time zero to infinity (AUC\[0-∞\]). AUC(0-∞) was calculated as the sum of the AUC to the last time point with a detectable plasma concentration (AUC\[0-last\]) and the extrapolated area given by the quotient of the last detectable concentration and the apparent terminal rate constant (λ).

Number of Participants With an Adverse Event (AE)
From administration of study drug through 14 days after administration of study drug

An AE is any unfavorable and unintended change in the structure, function or chemistry of the body temporally associated with study drug administration, whether or not considered related to the study drug.

Number of Participants Who Discontinued Study Due to an AE
From administration of study drug through 14 days after administration of study drug

An AE is any unfavorable and unintended change in the structure, function or chemistry of the body temporally associated with study drug administration, whether or not considered related to the study drug.

Area Under the Plasma Concentration Versus Time Curve (AUC) From Time Zero to Infinity (0-∞) After Single Dose Suvorexant: Moderate Hepatic Insufficiency Participants Versus Healthy Participants (Part I)
Predose and 0.5, 1, 2, 4, 6, 8, 12, 16, 24, 48, 72, 96, 120, and 144 hours post-dose

Overall exposure was assessed by the area under the plasma concentration versus time curve from time zero to infinity (AUC\[0-∞\]). AUC(0-∞) was calculated as the sum of the AUC to the last time point with a detectable plasma concentration (AUC\[0-last\]) and Ct/λ, where Ct was the last measurable concentration and λ was the apparent terminal rate constant.

AUC(0-∞) After Single Dose Suvorexant: Mild Hepatic Insufficiency Participants Versus Healthy Participants (Part II)
Predose and 0.5, 1, 2, 4, 6, 8, 12, 16, 24, 48, 72, 96, 120, and 144 hours post-dose

Overall exposure was assessed by the area under the plasma concentration versus time curve from time zero to infinity (AUC\[0-∞\]). AUC(0-∞) was calculated as the sum of the AUC to the last time point with a detectable plasma concentration (AUC\[0-last\]) and Ct/λ, where Ct was the last measurable concentration and λ was the apparent terminal rate constant.

Secondary Endpoints

Change from Baseline in Wakefulness after Persistent Sleep Onset at Week 8
Baseline and Week 8
Number of Participants Who are Positive for Substance Abuse at Day 1
Day 1
Number of Participants Who are Positive for Substance Abuse at Day 4
Day 4
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Study Design & Arms

AllocationRANDOMIZED
MaskingTRIPLE
ModelPARALLEL
PurposeTREATMENT

Treatment Arms

ArmTypeDescription
SuvorexantEXPERIMENTALParticipants receive 10 mg of suvorexant for the first three nights, increased to 20 mg of suvorexant nightly thereafter at the investigator's discretion, for up to approximately 8 weeks.
PlaceboPLACEBO_COMPARATORParticipants receive suvorexant-matching placebo for up to approximately 8 weeks.
Suvorexant HDEXPERIMENTALDrug
Suvorexant LDEXPERIMENTALDrug
Suvorexant ArmACTIVE_COMPARATOR -
Placebo ArmPLACEBO_COMPARATOR -
Poor sleep treatment groupEXPERIMENTAL100 participants will be randomized to take suvorexant 20mg daily at h.s. for 18-24 months
Poor sleep control gropPLACEBO_COMPARATOR100 participants will be randomized to take placebo daily at h.s. for 18-24 months
Suvorexant 10 mg → PlaceboEXPERIMENTALAfter an \~1- to 2-week single-blind placebo run-in period, participants received 10 mg suvorexant daily prior to bedtime for 4 weeks during Treatment Period 1, followed by a 1-week single-blind placebo washout period, followed by dose-matched placebo to suvorexant daily prior to bedtime during Treatment Period 2.
Placebo → Suvorexant 10 mgEXPERIMENTALAfter an \~1- to 2-week single-blind placebo run-in period, participants received dose-matched placebo to suvorexant daily prior to bedtime for 4 weeks during Treatment Period 1, followed by a 1-week single-blind placebo washout period, followed by 10 mg suvorexant daily prior to bedtime during Treatment Period 2.
Suvorexant 20 mg → PlaceboEXPERIMENTALAfter an \~1- to 2-week single-blind placebo run-in period, participants received 20 mg suvorexant daily prior to bedtime for 4 weeks during Treatment Period 1, followed by a 1-week single-blind placebo washout period, followed by dose-matched placebo to suvorexant daily prior to bedtime during Treatment Period 2.
Placebo → Suvorexant 20 mgEXPERIMENTALAfter an \~1- to 2-week single-blind placebo run-in period, participants received dose-matched placebo to suvorexant daily prior to bedtime for 4 weeks during Treatment Period 1, followed by a 1-week single-blind placebo washout period, followed by 20 mg suvorexant daily prior to bedtime during Treatment Period 2.
Suvorexant 40 mg → PlaceboEXPERIMENTALAfter an \~1- to 2-week single-blind placebo run-in period, participants received 40 mg suvorexant daily prior to bedtime for 4 weeks during Treatment Period 1, followed by a 1-week single-blind placebo washout period, followed by dose-matched placebo to suvorexant daily prior to bedtime during Treatment Period 2.
Placebo → Suvorexant 40 mgEXPERIMENTALAfter an \~1- to 2-week single-blind placebo run-in period, participants received dose-matched placebo to suvorexant daily prior to bedtime for 4 weeks during Treatment Period 1, followed by a 1-week single-blind placebo washout period, followed by 40 mg suvorexant daily prior to bedtime during Treatment Period 2.
Suvorexant 80 mg → PlaceboEXPERIMENTALAfter an \~1- to 2-week single-blind placebo run-in period, participants received 80 mg suvorexant daily prior to bedtime for 4 weeks during Treatment Period 1, followed by a 1-week single-blind placebo washout period, followed by dose-matched placebo to suvorexant daily prior to bedtime during Treatment Period 2.
Placebo → Suvorexant 80 mgEXPERIMENTALAfter an \~1- to 2-week single-blind placebo run-in period, participants received dose-matched placebo to suvorexant daily prior to bedtime for 4 weeks during Treatment Period 1, followed by a 1-week single-blind placebo washout period, followed by 80 mg suvorexant daily prior to bedtime during Treatment Period 2.
Suvorexant first, then placeboEXPERIMENTALDuring Period 1, participants \<65 years of age were administered a 40-mg oral dose of suvorexant once daily for 4 consecutive days in the evening and participants ≥65 years of age were administered a 30-mg oral dose of suvorexant once daily for 4 consecutive days in the evening. A washout period of at least 7 days followed Period 1. During Period 2, participants received one placebo tablet matching suvorexant, orally, once daily for 4 consecutive days in the evening.
Placebo first, then suvorexantEXPERIMENTALDuring Period 1, participants \<65 years of age received one placebo tablet matching suvorexant, orally, once daily for 4 consecutive days in the evening and participants ≥65 years of age received one placebo tablet matching suvorexant, orally, once daily for 4 consecutive days in the evening. A washout period of at least 7 days followed Period 1. During Period 2, participants were administered a 40-mg oral dose of suvorexant once daily for 4 consecutive days in the evening.
Suvorexant (40 mg)EXPERIMENTALIn Period 1, suvorexant (40 mg tablets) administered orally once daily for 4 consecutive days in the evening. Period 1 is followed by a washout period of a minimum of 5 days. Period 2 consists of placebo administered once daily for 4 consecutive days in the evening.
Participants with Severe Renal Impairment (Part I)EXPERIMENTALParticipants with severe renal impairment will receive a single dose of 20 mg open-label suvorexant during Part I of the study.
Healthy Participants (Severe Impairment Controls) (Part I)EXPERIMENTALHealthy participants matched to participants with severe renal impairment will receive a single dose of 20 mg open-label suvorexant during Part I of the study.
Participants with Moderate Renal Impairment (Part II)EXPERIMENTALParticipants with moderate renal impairment will receive a single dose of 20 mg open-label suvorexant during Part II of the study.
Healthy Participants (Moderate Impairment Controls) (Part II)EXPERIMENTALHealthy participants matched to participants with moderate renal impairment will receive a single dose of 20 mg open-label suvorexant during Part II of the study.
Participants with Mild Renal Impairment (Part II)EXPERIMENTALParticipants with mild renal impairment will receive a single dose of 20 mg open-label suvorexant during Part II of the study.
Healthy Participants (Mild Impairment Controls) (Part II)EXPERIMENTALHealthy participants matched to participants with mild renal impairment will receive a single dose of 20 mg open-label suvorexant during Part II of the study.
Participants with Moderate Hepatic Insufficiency (Part I)EXPERIMENTALParticipants with moderate hepatic insufficiency will receive a single dose of 20 mg open-label suvorexant during Part I of the study.
Healthy Participants (Part I)EXPERIMENTALHealthy participants matched to participants with moderate hepatic insufficiency will receive a single dose of 20 mg open-label suvorexant during Part I of the study.
Participants with Mild Hepatic Insufficiency (Part II)EXPERIMENTALParticipants with mild hepatic insufficiency will receive a single dose of 20 mg open-label suvorexant during Part II of the study (if conducted).
Healthy Participants (Part II)EXPERIMENTALHealthy participants matched to participants with mild hepatic insufficiency will receive a single dose of 20 mg open-label suvorexant during Part II of the study (if conducted).

Interventions

NameTypeDescription
SuvorexantDRUGOral Tablet
PlaceboDRUGOral Tablet
Suvorexant High Dose (HD)DRUGSuvorexant 40 mg + placebo matching suvorexant 20 mg for participants \<65 years old; Suvorexant 30 mg + placebo matching suvorexant 15 mg for participants ≥65 years old; all study drug is tablet for oral administration, taken once daily at bedtime. Participants receive this dose during the 3-month TRT Phase and, if applicable, the optional 3-month EXT Phase. During the 1-week double-blind (DB) Run-out (RO) following the TRT/EXT phase, participants in this study arm receive the noted suvorexant dose or placebo, in a 1:1 ratio. During the 2-week single-blind Run-in period prior to randomization all participants receive placebo to suvorexant once daily at bedtime.
Suvorexant Low Dose (LD)DRUGSuvorexant 20 mg + placebo matching suvorexant 40 mg for participants \<65 years old; Suvorexant 15 mg + placebo matching suvorexant 30 mg for participants ≥65 years old; all study drug is tablet for oral administration, taken once daily at bedtime. Participants receive this dose during the 3-month TRT Phase and, if applicable, the optional 3-month EXT Phase. During the 1-week DB RO following the TRT/EXT phase, participants in this study arm receive the noted suvorexant dose or placebo, in a 1:1 ratio. During the 2-week single-blind Run-in period prior to randomization all participants receive placebo to suvorexant once daily at bedtime.
Comparator: PlaceboDRUGMatching placebos to suvorexant 40 mg and 20 mg for participants \<65 years old; matching placebos to suvorexant 30 mg and 15 mg for participants ≥65 years old; all study drug is tablet for oral administration, taken once daily at bedtime. Placebo is a third treatment arm for comparison to the two active (suvorexant) treatment arms during the 3-month TRT Phase and, if applicable, the optional 3-month EXT Phase. During the 1-week DB RO following the TRT/EXT phase, participants in this study arm continue to receive placebo. During the 2-week single-blind Run-in period prior to randomization all participants receive placebo to suvorexant once daily at bedtime.
Dose-matched Placebo to SuvorexantDRUGOral tablet, administered daily before bedtime
Suvorexant 20 mgDRUGAdminister Suvorexant versus placebo every evening for Post-Operative Day (POD) 0,1, \&2
Matching PlaceboDRUGPlacebo tablets, orally once daily for 4 consecutive days in the evening
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Eligibility Criteria

Age Range18 Years to 70 Years
SexALL
Healthy VolunteersNo
Study Sites13

Inclusion Criteria: The main inclusion criteria include but are not limited to the following: * Has a primary diagnosis of OUD according to Diagnostic and Statistical Manual of Mental Disorder, 5th Edition (DSM-5), and confirmed through the Mini International Neuropsychiatric Interview (MINI). * I...

Countries:United StatesJapan
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Recent Changes (Last 90 Days)

LOWAug 28, 2026NCT06655883lastUpdatePostDate: changed
LOWAug 28, 2026NCT06655883lastUpdatePostDate: changed
LOWAug 14, 2026NCT06655883lastUpdatePostDate: changed
LOWAug 14, 2026NCT06655883lastUpdatePostDate: changed

Frequently asked questions about Suvorexant

What is Suvorexant used for?

Suvorexant is an investigational small molecule being developed for insomnia and sleep-related conditions, including primary insomnia, sleep initiation and maintenance disorders, and sleep apnea. It is also being studied for delirium. The drug is in Phase 3 clinical development for these psychiatric indications.

Who makes Suvorexant?

Suvorexant is being developed by Merck & Company, Inc., which trades under the ticker MRK. The company is conducting clinical trials to evaluate the drug for insomnia and related sleep disorders.

What phase is Suvorexant in?

Suvorexant is in Phase 3 clinical development. It is an investigational drug and has not been approved by regulatory authorities. The most advanced trial is a long-term safety study in participants with primary insomnia.

What clinical trials is Suvorexant in?

Suvorexant has been studied in several clinical trials. A Phase 3 trial (NCT01021813) evaluated long-term safety in 781 participants with insomnia. Phase 1 trials include NCT01043926 in hepatic insufficiency, NCT01059851 in renal impairment, and NCT01293006 in patients with COPD.

Is Suvorexant the same as Suvorexant 20 mg?

Yes, Suvorexant 20 mg is an alternative name for Suvorexant. The drug is being developed by Merck & Company, Inc. for insomnia and related sleep disorders, and is currently in Phase 3 clinical trials.