Optimal Dosage of Acetazolamide for OSA Treatment

September 18, 2025 updated by: University Hospital, Antwerp

Optimal Dosage of Acetazolamide for Obstructive Sleep Apnea Treatment: a Parallel-group, Double-blind, Placebo-controlled, Randomized Trial

Acetazolamide, a carbonic anhydrase inhibitor, has received some attention as potential treatment for obstructive sleep apnea (OSA). It produces a metabolic acidosis by excreting bicarbonate, thereby stimulating baseline ventilation. Evidence suggests that acetazolamide primarily improves ventilatory control instability (expressed as loop gain), which is an important contributor to the pathophysiology of OSA.

Few studies have assessed the efficacy of acetazolamide in patients with OSA. Since most of them had a small sample size and used different therapeutic dosages, clinical applications are currently limited. Therefore, this study aims to compare the effect of two acetazolamide dosages on the severity and pathophysiology of OSA.

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.

Detailed Description

In this double-blind, parallel-group, controlled trial, eligible patients will be randomized into one of the following treatment arms: (1) placebo, (2) 250 mg of acetazolamide, or (3) 500 mg of acetazolamide. After 4 weeks, treatment outcome will be assessed by in-laboratory polysomnography. Additionally, arterial blood gas analysis and lung function tests will be performed before and during treatment.

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.
91

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
    • Antwerp
      • Edegem, Antwerp, Belgium, 2650
        • Antwerp University Hospital

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

18 years to 79 years (Adult, Older Adult)

Accepts Healthy Volunteers

No

Description

Inclusion Criteria:

  • AHI between 15 and 65 events/hour
  • BMI < 35 kg/m²

Exclusion Criteria:

  • Craniofacial anomalies
  • Central sleep apnea (defined as central AHI > 25% of total AHI)

  • Contra-indications related to acetazolamide treatment

    • Hypersensitivity to sulphonamides or acetazolamide
    • Renal impairment, electrolyte imbalances, and/or adrenocortical insufficiency
    • Clinically significant metabolic, hepatic, and/or hematological disease
    • Chronic obstructive pulmonary disease
    • Closed-angle glaucoma
  • Conditions likely to affect OSA physiology: neuromuscular disease or other major neurological disorders, heart failure, or any other unstable major medical condition.
  • Intake of drugs that substantially stimulate or depress respiration, including benzodiazepines, opioids, theophylline, and pseudoephedrine
  • Inadequately treated sleep disorders other than OSA that would confound functional sleep assessment
  • Inability of the patient to understand and/or comply to the study procedures
  • Active psychiatric disease (psychotic illness, major depression, anxiety attacks, alcohol or drug abuse)
  • Pregnancy

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: Randomized
  • Interventional Model: Parallel Assignment
  • Masking: Double

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: Low dose acetazolamide
Unembellished white tablets. The drug should be taken one hour before bedtime. Total treatment duration will be 6 weeks.
Drug: Acetazolamide
250 mg once daily
Other Names:
  • Diamox
  • ATC code: S01EC01
Drug: Acetazolamide
500 mg once daily
Other Names:
  • Diamox
  • ATC code: S01EC01
Experimental: High dose acetazolamide
Unembellished white tablets. The drug should be taken one hour before bedtime. Total treatment duration will be 6 weeks.
Drug: Acetazolamide
250 mg once daily
Other Names:
  • Diamox
  • ATC code: S01EC01
Drug: Acetazolamide
500 mg once daily
Other Names:
  • Diamox
  • ATC code: S01EC01
Placebo Comparator: Placebo
Matching placebo tablets. The drug should be taken one hour before bedtime. Total treatment duration will be 6 weeks.
Other: Placebo
Once daily

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
Apnea-hypopnea index (AHI)
Time Frame: 4 weeks
Change in AHI (events/hour) from baseline to follow-up. The AHI is a measure of sleep apnea severity that encompasses the frequency of apneas (cessations in breathing) and hypopneas (reductions in airflow).
4 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
Measure Description
Time Frame
Pathophysiological traits
Time Frame: 4 weeks
Changes in pathophysiological traits (Vpassive, Vactive, Arousal Threshold, Loop Gain) will be quantified as %Veupnea from polysomnography data using a validated algorithm.
4 weeks
Percent responders
Time Frame: 4 weeks
Treatment response will be defined as a reduction in AHI of ≥ 50%.
4 weeks
Nocturnal oxygen saturation
Time Frame: 4 weeks
Change in mean and minimal SaO2 (%).
4 weeks
Oxygen desaturation index (ODI)
Time Frame: 4 weeks
Change in ODI (events/hour) from baseline to follow-up. The ODI represents the average number of desaturation episodes (≥ 3%) per hour sleep.
4 weeks
Arterial blood gas measurements
Time Frame: 4 weeks
Change in pO2 (mmhg) and pCO2 (mmhg) from baseline to follow-up.
4 weeks
Lung function parameters
Time Frame: 4 weeks
Change in flow-volume curve from baseline to follow-up.
4 weeks
Daytime sleepiness: Epworth Sleepiness Scale (ESS)
Time Frame: 6 weeks
The ESS asks respondents to rate on a 4-point scale (0-3) their usual chances of dozing off or falling asleep while engaged in eight different activities. The ESS score (the sum of 8 item scores) can range from 0 to 24. The higher the ESS score, the higher that person's sleep propensity in daily life. A score higher than 10 indicates the presence of excessive daytime sleepiness.
6 weeks
Sleep-related quality of life: Functional Outcome of Sleep Questionnaire (FOSQ-10)
Time Frame: 6 weeks
This questionnaire is an abbreviated version of the original 30-item version. The FOSQ-10 consists of 10 items that are distributed among 5 subscales: general productivity (2 items), activity level (3 items), vigilance (3 items), social outcomes (1 item), and intimacy and sexual relationships (1 item). The questionnaire has a 4-point scale. The total score is calculated as the sum of the subscale means and can range from 5 to 20. The minimal important difference ranges from 1.7 to 2.0 points.
6 weeks
Snoring intensity: Visual Analogue Scale (VAS)
Time Frame: 6 weeks
A standard 10-point VAS ranging from 0 (no snoring) to 10 (extreme snoring) will be used to evaluate the subjective status of snoring during sleep. Heavy snoring corresponds to a snoring index of at least 7. A decrease of 3 points after treatment is considered significant. To be considered as an important reduction, snoring needs to reduce to an index that is no longer experienced as bothersome (i.e. < 3).
6 weeks

Other Outcome Measures

Other Outcome Measures

For clinical trials, a planned measurement described in the protocol that is used to determine the effect of an intervention/treatment on participants. For observational studies, a measurement or observation that is used to describe patterns of diseases or traits, or associations with exposures, risk factors, or treatment. Types of outcome measures include primary outcome measure and secondary outcome measure.
Outcome Measure
Measure Description
Time Frame
Incidence of adverse events
Time Frame: 6 weeks
Safety and tolerability of study treatment.
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.
University Hospital, Antwerp

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.
  • Principal Investigator: Olivier Vanderveken, MD, PhD, University Hospital, Antwerp

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.
April 20, 2021

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.
March 19, 2024

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.
May 5, 2024

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).
January 26, 2021

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.
January 26, 2021

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.
January 27, 2021

Study Record Updates

Last Update Posted (Estimated)

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.
September 24, 2025

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.
September 18, 2025

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.
September 1, 2025

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.
  • B3002021000015

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

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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