Study of MK-6552 in Participants With Narcolepsy Type 1 (MK-6552-004)

Inclusion Criteria: * Has a diagnosis of NT1, including a valid polysomnography within the previous 5 years and a current diagnosis of NT1 for at least 6 months based on criteria established by the International Classification of Sleep Disorders- Third Edition, or Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) \[American Psychiatric Association 2013\] * Is positive for HLA-DQB1\*06:02 allele supporting a diagnosis of NT1 * Has a baseline history of unequivocal cataplexy prior to initiation of anti-cataplexy medications * Reports a total sleep time of \> 6 hours on at least 4 out of 7 nights each week within the 4 weeks prior to screening visit Exclusion Criteria: * Has history of or current hypertension * Has underlying cardiovascular or cerebrovascular conditions in which an acute rise in blood pressure would pose a clinical concern, including but nor limited to aneurysms or arteriovenous malformations * Has a history of renal or hepatic impairment * Has a history of cardiac ischemia or cerebral ischemia including but not limited to history of stroke, transient ischemic attack, or transient global amnesia * Based on clinical interview and responses on the Columbia-Suicide Severity Rating Scale, is at imminent risk of self-harm or of harm to others in the opinion of the investigator * Mentally or legally incapacitated, has significant emotional problems at the time of prestudy (screening) visit or expected during the conduct of the study or has a history of clinically significant psychiatric disorder of the last 5 years * History of cancer (malignancy) * Has a history of any of the following sleep disorders: obstructive sleep apnea (OSA) defined as an Apnea Hypopnea Index \> 15 per hour per the American Academy of Sleep Medicine alternate criteria, primary insomnia (within the past 6 months), circadian rhythm sleep disorder, shift work sleep disorder (within the past 6 months), clinically significant parasomnia at the discretion of the investigator * Has a history of seizure disorder, clinically significant head trauma, or past invasive intracranial surgery or clinically significant dementia * Positive test(s) for Hepatitis B surface antigen, hepatitis C antibodies, or human immunodeficiency virus