HighCycle Study: Effect of Acetazolamide on Sleep Disordered Breathing in Women Compared to Men

June 3, 2026 updated by: University of Zurich

HighCycle Study: Effect of Acetazolamide on Sleep Disordered Breathing in Women. A Randomized, Placebo-Controlled, Double-Blind Parallel Trial.

Randomized clinical trial evaluating the effect of acetazolamide on sleep disordered breathing in women compared to men travelling to 3600 m.

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.
303

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 Contact Backup

Study Locations

  • Kyrgyzstan
    • Bishkek
      • Bishkek, Bishkek, Kyrgyzstan, 720040
        • National center for cardiology and internal medicine

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

Accepts Healthy Volunteers

Yes

Description

Inclusion Criteria:

  • Healthy, non-smoking men and women, age 18-44 years, without any diseases and need of regular medication (including oral contraceptives).
  • BMI >18 kg/m2 and <30 kg/m2
  • Born, raised and currently living at altitudes <1000 m
  • Written informed consent
  • Premenopausal women with an eumenorrheic cycle

Exclusion Criteria:

  • Other types of contraceptvies (hormonal intrauterine device, vaginal ring, subcutaneous injections or implants, among others)
  • Pregnancy or nursing
  • Anaemic (haemoglobin concentration <10g/dl)
  • Any altitude trip <4 weks before the study
  • Allergy to acetazolamide and other sulfonamides

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: Prevention
  • Allocation: Randomized
  • Interventional Model: Parallel Assignment
  • Masking: Quadruple

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.
Active Comparator: WOMEN - ACETAZOLAMIDE oral capsule
Acetazolamide 250 mg/day (capsules @125 mg; 1 in the morning, 1 in the evening), orally. Medication starts 24 hours before ascent to 3600 m until the morning after the second night at 3600 m.
Drug: Acetazolamide
Administration of 1x125mg acetazolamide in the morning, 1x125mg in the evening, starting 24 hours before departure to 3600 m.
Active Comparator: MEN - ACETAZOLAMIDE oral capsule
Acetazolamide 250 mg/day (capsules @125 mg; 1 in the morning, 1 in the evening), orally. Medication starts 24 hours before ascent to 3600 m until the morning after the second night at 3600 m.
Drug: Acetazolamide
Administration of 1x125mg acetazolamide in the morning, 1x125mg in the evening, starting 24 hours before departure to 3600 m.
Placebo Comparator: WOMEN - PLACEBO oral capsule
Placebo (capsules identically looking as acetazolamide capsules; 1 in the morning, 1 in the evening), orally. Medication starts 24 hours before ascent to 3600 m until the morning after the second night at 3600 m.
Drug: Placebo
Administration of equally looking placebo capsules in the morning and in the evening, starting 24 hours before departure to 3600 m.
Placebo Comparator: MEN - PLACEBO oral capsule
Placebo (capsules identically looking as acetazolamide capsules; 1 in the morning, 1 in the evening), orally. Medication starts 24 hours before ascent to 3600 m until the morning after the second night at 3600 m.
Drug: Placebo
Administration of equally looking placebo capsules in the morning and in the evening, starting 24 hours before departure to 3600 m.

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
Measure Description
Time Frame
Nocturnal oxygen desaturation index (ODI)
Time Frame: Night 1 at 760 m and Night 1 at 3600 m
Sex-related difference in the altitude-induced change in the ODI (number of ∆SpO2 >3% per hour time in bed measured by pulse oximetry) between acetazolamide and placebo group.
Night 1 at 760 m and Night 1 at 3600 m

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
Measure Description
Time Frame
Nocturnal oxygen saturation (SpO2)
Time Frame: Night 1 at 760 m and Night 1 at 3600 m
Sex-related difference in the altitude-induced change in the mean nocturnal oxygen saturation measured by pulse oximetry between acetazolamide and placebo group.
Night 1 at 760 m and Night 1 at 3600 m
Nocturnal oxygen saturation (SpO2)
Time Frame: Night 1 at 760 m and Night 2 at 3600 m
Sex-related difference in the altitude-induced change in the mean nocturnal oxygen saturation measured by pulse oximetry between acetazolamide and placebo group.
Night 1 at 760 m and Night 2 at 3600 m
Apnea/hypopnea index (AHI)
Time Frame: Night 1 at 760 m and Night 1 at 3600 m
Sex-related difference in the altitude-induced change in the mean number of apneas/hypopneas per hour between the acetazolamide and placebo group.
Night 1 at 760 m and Night 1 at 3600 m
Apnea/hypopnea index (AHI)
Time Frame: Night 1 at 760 m and Night 2 at 3600 m
Sex-related difference in the altitude-induced change in the mean number of apneas/hypopneas per hour between the acetazolamide and placebo group.
Night 1 at 760 m and Night 2 at 3600 m
Subjective sleep quality
Time Frame: Night 1 at 760 m and Night 1 at 3600 m
Sex-related difference in the altitude-induced change in subjective sleep quality assessed by a 100-mm visual analog scale between the acetazolamide and placebo group.
Night 1 at 760 m and Night 1 at 3600 m
Subjective sleep quality
Time Frame: Night 1 at 760 m and Night 2 at 3600 m
Sex-related difference in the altitude-induced change in subjective sleep quality assessed by a 100-mm visual analog scale between the acetazolamide and placebo group.
Night 1 at 760 m and Night 2 at 3600 m
Nocturnal oxygen desaturation index (ODI)
Time Frame: Night 1 at 760 m and Night 2 at 3600 m
Sex-related difference in the altitude-induced change in the ODI (number of ∆SpO2 >3% per hour time in bed measured by pulse oximetry) between acetazolamide and placebo group.
Night 1 at 760 m and Night 2 at 3600 m

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.
University of Zurich

Collaborators

Collaborators

An organization other than the sponsor that provides support for a clinical study. This support may include activities related to funding, design, implementation, data analysis, or reporting.
University Hospital Heidelberg
National Center of Cardiology and Internal Medicine named after academician M.Mirrakhimov
Laboratoire des Adaptations Métaboliques à l'Exercice en conditions Physiologiques et Pathologiques

Investigators

Investigators

A researcher involved in a clinical study. Related terms include site principal investigator, site sub-investigator, study chair, study director, and study principal investigator.
  • Study Chair: Michael Furian, Prof. Dr., University of Zurich
  • Study Director: Talant Sooronbaev, Prof. Dr., National Center of Cardiology and Internal Medicine, Bishkek, Kyrgyzstan

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.
July 15, 2024

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.
August 31, 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.
August 31, 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).
July 5, 2024

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.
July 5, 2024

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.
July 12, 2024

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.
June 5, 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.
June 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.
June 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.
  • HighCycle_SDB

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

UNDECIDED

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

product manufactured in and exported from the U.S.

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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