A Switch Study From High-Sodium Oxybate to Xywav to Evaluate Changes in Blood Pressure in Participants With Narcolepsy (XYLO)

April 3, 2026 updated by: Jazz Pharmaceuticals

An Open-Label, Multicenter Switch Study Evaluating Changes in Blood Pressure in Participants With Narcolepsy Switching From High-Sodium Oxybate to Xywav

The aim of this study is to quantify the change in blood pressure when participants with narcolepsy treated with high-sodium oxybate are transitioned to Xywav, a low-sodium oxybate. The results of this study may provide health care providers (HCPs), patients, and payers with important new information regarding BP changes related to differences in sodium content between available oxybates for the treatment of narcolepsy.

Study Overview

Status

Status

Indicates the current recruitment status or the expanded access status.
Completed

Conditions

Conditions

The disease, disorder, syndrome, illness, or injury that is being studied. On ClinicalTrials.gov, conditions may also include other health-related issues, such as lifespan, quality of life, and health risks.

Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.

Study Type

Study Type

Describes the nature of a clinical study. Study types include interventional studies (also called clinical trials), observational studies (including patient registries), and expanded access.
Interventional

Enrollment (Actual)

Enrollment

The number of participants in a clinical study. The "anticipated" enrollment is the target number of participants that the researchers need for the study.
155

Phase

Phase

The stage of a clinical trial studying a drug or biological product, based on definitions developed by the U.S. Food and Drug Administration (FDA). The phase is based on the study's objective, the number of participants, and other characteristics. There are five phases: Early Phase 1 (formerly listed as Phase 0), Phase 1, Phase 2, Phase 3, and Phase 4. Not Applicable is used to describe trials without FDA-defined phases, including trials of devices or behavioral interventions.
  • Phase 4

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

Study Contact

The name and contact information for the person who can answer enrollment questions for a clinical study. Each location where the study is being conducted may also have a specific contact, who may be better able to answer those questions.

Study Locations

  • Belgium
      • Edegem, Belgium, 2650
        • Antwerp University Hospital (UZA)
      • Namur, Belgium, 5101
        • Private Practice RESPISOM Namur
  • France
    • Herault
      • Montpellier, Herault, France, 34295
        • Hôpital Gui de Chauliac
    • Isere
      • Grenoble, Isere, France, 38043
        • CHU de Grenoble - Hôpital Albert Michallon
    • Loire Atlantique
      • Nantes, Loire Atlantique, France, 44093
        • CHU Nantes - Hôtel Dieu
  • Italy
      • Bologna, Italy, 40139
        • IRCCS Istituto de Scienze Neurologiche di Bologna (ISNB)
      • Milan, Italy, 20127
        • Ospedale San Raffaele (San Raffaele Turro)
      • Roma, Italy, 00133
        • Azienda Ospedaliera Universitaria Policlinico Tor Vergata
  • Spain
      • Barcelona, Spain, 08035
        • Hospital Universitari Vall d'Hebron
      • Castellon, Spain, 12004
        • Hospital General de Castellon
      • Madrid, Spain, 28040
        • Hospital Universitario Clinico San Carlos
    • Alava
      • Vitoria-Gasteiz, Alava, Spain, 01004
        • Hospital Universitario Araba - Sede Santiago
  • United States
    • California
      • Culver City, California, United States, 90230
        • Science 37
      • Encino, California, United States, 91436
        • M3 Wake Research
      • Huntington Beach, California, United States, 92647
        • So Cal Clinical Research
      • Lakewood, California, United States, 90805
        • Long Beach Research Institute
      • Redwood City, California, United States, 94063
        • Stanford School of Medicine
      • San Ramon, California, United States, 94583
        • TriValley Sleep Center
      • Santa Ana, California, United States, 92705
        • SDS Clinical Trials, Inc.
    • Florida
      • Boca Raton, Florida, United States, 33486
        • FWD Clinical Research
      • Brandon, Florida, United States, 33511
        • Meris Clinical Research, LLC
      • Miami, Florida, United States, 33169
        • Ocean Wellness Center
      • Miami, Florida, United States, 33176
        • Serenity Research Center LLC
      • Orlando, Florida, United States, 32804
        • Florida Pediatric Research Institute, LLC
    • Georgia
      • Macon, Georgia, United States, 31210
        • Sleep Practitioners, LLC
    • Idaho
      • Nampa, Idaho, United States, 83686
        • Saltzer Medical Group
    • Kentucky
      • Louisville, Kentucky, United States, 40202
        • University of Louisville
    • Maryland
      • Baltimore, Maryland, United States, 21201
        • University of Maryland Medical Center
    • Massachusetts
      • Newton, Massachusetts, United States, 02459
        • Neurocare, Inc
    • Michigan
      • Lansing, Michigan, United States, 48911
        • Sparrow Health System
    • Nebraska
      • Lincoln, Nebraska, United States, 68506
        • Bryan Medical Center
    • Nevada
      • Henderson, Nevada, United States, 89052
        • Henderson Clinical Trials LLC
    • North Carolina
      • Huntersville, North Carolina, United States, 28078
        • Advanced Respiratory and Sleep Medicine, PLLC
    • Ohio
      • Cincinnati, Ohio, United States, 45245
        • Intrepid Research, LLC
      • Cleveland, Ohio, United States, 44106
        • University Hospitals Cleveland Medical Center
      • Dublin, Ohio, United States, 43017
        • Ohio Sleep Medicine and Neuroscience
    • Oregon
      • Portland, Oregon, United States, 97239
        • OHSU Hospital
    • Pennsylvania
      • Abington, Pennsylvania, United States, 19001
        • Abington Neurological Associates, LTD
    • South Carolina
      • Columbia, South Carolina, United States, 29201
        • Bogan Sleep Consultants, LLC
      • Greenville, South Carolina, United States, 29615
        • Velocity Clinical Research, Greenville
      • Rock Hill, South Carolina, United States, 29732
        • Clinical Research of Rock Hill
    • Texas
      • Austin, Texas, United States, 78731
        • FutureSearch Trials of Neurology
      • San Antonio, Texas, United States, 78229
        • Sleep Therapy & Research Center

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Eligibility Criteria

The key requirements that people who want to participate in a clinical study must meet or the characteristics they must have. Eligibility criteria consist of both inclusion criteria (which are required for a person to participate in the study) and exclusion criteria (which prevent a person from participating). Types of eligibility criteria include whether a study accepts healthy volunteers, has age or age group requirements, or is limited by sex.

Ages Eligible for Study

  • Adult
  • Older Adult

Accepts Healthy Volunteers

No

Description

Key Inclusion Criteria:

  • Participants must be 18 to 70 years of age inclusive, at the time of signing the informed consent.
  • Participants have a documented diagnosis of Type 1 or Type 2 narcolepsy that meets International Classification of Sleep Disorders (ICSD)-3 or Diagnostic and Statistical Manual of Mental Disorders (DSM)-5 criteria.
  • Participants must have been receiving a total dose of high-sodium oxybate (eg, XYREM) of 6 to 9 g/night (inclusive) with twice-nightly dosing for a minimum of 6 consecutive weeks prior to screening.
  • If currently treated with stimulants and/or alerting agents or other medications known to affect BP, participant must have been taking the same dosing regimen for at least 2 months prior to screening and agree to take the same dose throughout the study.
  • If currently taking stable doses of antihypertensive therapies, participant must maintain these treatments at the same dose throughout the study unless otherwise advised by their medical care
  • Participant is male or female. A female participant is eligible to participate if she is not pregnant or breastfeeding, if she is a woman of nonchildbearing potential or is a woman of childbearing potential and using a contraceptive method that is highly effective.

Key Exclusion Criteria:

  • History or presence of any acutely unstable medical condition, behavioral or psychiatric disorder (including active suicidal ideation), or surgical history that could affect the safety of the participant or interfere with study assessments or the ability of the participant to complete the study based on the judgment of the investigator.
  • Presence of significant cardiovascular disease or cardiovascular condition that in the investigator's opinion may jeopardize participant safety in the study, including screening ECG results.
  • Presence of atrial fibrillation detected on screening electrocardiogram (ECG).
  • Presence of resistant hypertension.

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Treatment
  • Allocation: N/A
  • Interventional Model: Single Group Assignment
  • Masking: None (Open Label)

Arms and Interventions

Participant Group / Arm

Participant Group / Arm

A group or subgroup of participants in a clinical trial that receives a specific intervention/treatment, or no intervention, according to the trial's protocol.
Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.
Experimental: JZP258
Eligible participants will be switched, on a gram-for-gram basis, from their prescribed twice-nightly high-sodium oxybate (such as xyrem) to Xywav. Participants who, in the opinion of the investigator, require an adjustment to their Xywav dosing, can increase or decrease their dose by 1.5 grams per night as long as the participant's total nightly dose is between 6 to 9 grams per night.
Drug: JZP258
0.5 g/ml calcium, magnesium, potassium, and sodium oxybates oral solution
Other Names:
  • Xywav

What is the study measuring?

Primary Outcome Measures

Primary Outcome Measures

In a clinical study's protocol, the planned outcome measure that is the most important for evaluating the effect of an intervention/treatment. Most clinical studies have one primary outcome measure, but some have more than one.
Outcome Measure
Time Frame
Change From Baseline to End of Treatment (EOT) Visit on the 24-hour Average Systolic Blood Pressure (SBP) in mmHg
Time Frame: Baseline (Screening) and End of Treatment (EOT) Visit, up to 6 weeks
Baseline (Screening) and End of Treatment (EOT) Visit, up to 6 weeks

Secondary Outcome Measures

Secondary Outcome Measures

In a clinical study's protocol, a planned outcome measure that is not as important as the primary outcome measure for evaluating the effect of an intervention but is still of interest. Most clinical studies have more than one secondary outcome measure.
Outcome Measure
Time Frame
Change From Baseline to EOT Visit on the Daytime Average SBP in mmHg
Time Frame: Baseline (Screening) and End of Treatment (EOT) Visit, up to 6 weeks
Baseline (Screening) and End of Treatment (EOT) Visit, up to 6 weeks
Change From Baseline to EOT Visit on the Seated Resting Average SBP in mmHg
Time Frame: Baseline (Screening) and End of Treatment (EOT) Visit, up to 6 weeks
Baseline (Screening) and End of Treatment (EOT) Visit, up to 6 weeks
Change From Baseline to EOT Visit on the Nighttime Average SBP in mmHg
Time Frame: Baseline (Screening) and End of Treatment (EOT) Visit, up to 6 weeks
Baseline (Screening) and End of Treatment (EOT) Visit, up to 6 weeks

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Sponsor

The organization or person who initiates the study and who has authority and control over the study.
Jazz Pharmaceuticals

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

General Publications

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

Study Start

The actual date on which the first participant was enrolled in a clinical study. The "anticipated" study start date is the date that the researchers think will be the study start date.
June 26, 2023

Primary Completion (Actual)

Primary Completion

The date on which the last participant in a clinical study was examined or received an intervention to collect final data for the primary outcome measure. Whether the clinical study ended according to the protocol or was terminated does not affect this date. For clinical studies with more than one primary outcome measure with different completion dates, this term refers to the date on which data collection is completed for all the primary outcome measures. The "anticipated" primary completion date is the date that the researchers think will be the primary completion date for the study.
February 25, 2025

Study Completion (Actual)

Study Completion

The date on which the last participant in a clinical study was examined or received an intervention/treatment to collect final data for the primary outcome measures, secondary outcome measures, and adverse events (that is, the last participant's last visit). The "anticipated" study completion date is the date that the researchers think will be the study completion date.
March 10, 2025

Study Registration Dates

First Submitted

First Submitted

The date on which the study sponsor or investigator first submitted a study record to ClinicalTrials.gov. There is typically a delay of a few days between the first submitted date and the record's availability on ClinicalTrials.gov (the first posted date).
May 12, 2023

First Submitted That Met QC Criteria

First Submitted That Met QC Criteria

The date on which the study sponsor or investigator first submits a study record that is consistent with National Library of Medicine (NLM) quality control (QC) review criteria. The sponsor or investigator may need to revise and submit a study record one or more times before NLM's QC review criteria are met. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
May 12, 2023

First Posted (Actual)

First Posted

The date on which the study record was first available on ClinicalTrials.gov after National Library of Medicine (NLM) quality control (QC) review has concluded. There is typically a delay of a few days between the date the study sponsor or investigator submitted the study record and the first posted date.
May 22, 2023

Study Record Updates

Last Update Posted (Actual)

Last Update Posted

The most recent date on which changes to a study record were made available on ClinicalTrials.gov. There may be a delay between when the changes were submitted to ClinicalTrials.gov by the study's sponsor or investigator (the last update submitted date) and the last update posted date.
April 24, 2026

Last Update Submitted That Met QC Criteria

Last Update Submitted That Met QC Criteria

The most recent date on which the study sponsor or investigator submitted changes to a study record that are consistent with National Library of Medicine (NLM) quality control (QC) review criteria. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
April 3, 2026

Last Verified

Last Verified

The most recent date on which the study sponsor or investigator confirmed the information about a clinical study on ClinicalTrials.gov as accurate and current. If a study with a recruitment status of recruiting; not yet recruiting; or active, not recruiting has not been confirmed within the past 2 years, the study's recruitment status is shown as unknown.
April 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

Other Study ID Numbers

Identifiers or ID numbers other than the NCT number that are assigned to a clinical study by the study's sponsor, funders, or others. These numbers may include unique identifiers from other trial registries and National Institutes of Health grant numbers.
  • JZP258-406

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

YES

IPD Plan Description

In accordance with ICMJE requirements, Jazz Pharmaceuticals may provide qualified external researchers access to individual participant data (IPD) and clinical trial data that underlie the results of this trial upon request. Qualified researchers can submit a request on https://www.jazzpharma.com/science/clinical-trial-data-sharing/ as outlined. Jazz Pharmaceuticals reserves the right not to consider a request. For inquiries about Jazz's data sharing policy contact clinicaldatasharing@jazzpharma.com.

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

Yes

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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