Obstructive Sleep ApneaPhase 4NCT04726982
Optimal Dosage of Acetazolamide for OSA Treatment
A Phase 4 study testing Acetazolamide in people with Obstructive Sleep Apnea, run by University Hospital, Antwerp at 1 site in Belgium.
Trial summary
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. Read more about this study
- Who is it for?
- Ages 18 to 79 years
- Conditions the study is for
- Obstructive Sleep Apnea
- What is being tested?
- Acetazolamide
- Type of treatment
- Pill or oral medicine
- Could I receive a placebo?
- Yes, some participants may receive a placebo
- How many people
- 91 participants
- Where
- 1 siteBelgium
- Study dates
- 20 Apr 2021to 5 May 2024
- Phase
- Phase 4
- Are there results?
- None posted in the registry
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 18 to 79 years
- All sexes
- No healthy volunteers
- Adult, Older adult
Who may be able to join
- AHI between 15 and 65 events/hour
- BMI < 35 kg/m²
Who cannot join
- 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
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- 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
Trial locations and contacts
1 site in 1 country.
About this study
Official title: 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.
Read the 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.
- Conditions
- Obstructive Sleep Apnea
- Being tested
- Acetazolamide, Placebo
- Keywords
- Carbonic anhydrase inhibitor, Treatment, Pharmacotherapy, Sleep apnea, Loop gain, Respiration, Ventilatory control instability, Acidosis
- Medical subject headings
- Sleep Apnea, Obstructive, Sleep Apnea Syndromes, Respiratory Aspiration, Acidosis
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
AcetazolamideDrug
Also called Diamox, ATC code: S01EC01
250 mg once daily
AcetazolamideDrug
Also called Diamox, ATC code: S01EC01
500 mg once daily
PlaceboOther
Once daily
| Study group | Role | What they receive |
|---|---|---|
| Low dose acetazolamide | Experimental | Unembellished white tablets. The drug should be taken one hour before bedtime. Total treatment duration will be 6 weeks. Receives: Drug: Acetazolamide |
| High dose acetazolamide | Experimental | Unembellished white tablets. The drug should be taken one hour before bedtime. Total treatment duration will be 6 weeks. Receives: Drug: Acetazolamide |
| Placebo | Placebo comparator | Matching placebo tablets. The drug should be taken one hour before bedtime. Total treatment duration will be 6 weeks. Receives: Other: Placebo |
What is being measured
The primary outcome is the main question the study is designed to answer.
Apnea-hypopnea index (AHI)
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).
Measured: 4 weeks
Secondary outcomes (9)
Pathophysiological traits
Changes in pathophysiological traits (Vpassive, Vactive, Arousal Threshold, Loop Gain) will be quantified as %Veupnea from polysomnography data using a validated algorithm.
Measured: 4 weeks
Percent responders
Treatment response will be defined as a reduction in AHI of ≥ 50%.
Measured: 4 weeks
Nocturnal oxygen saturation
Change in mean and minimal SaO2 (%).
Measured: 4 weeks
Oxygen desaturation index (ODI)
Change in ODI (events/hour) from baseline to follow-up. The ODI represents the average number of desaturation episodes (≥ 3%) per hour sleep.
Measured: 4 weeks
Arterial blood gas measurements
Change in pO2 (mmhg) and pCO2 (mmhg) from baseline to follow-up.
Measured: 4 weeks
Lung function parameters
Change in flow-volume curve from baseline to follow-up.
Measured: 4 weeks
Daytime sleepiness: Epworth Sleepiness Scale (ESS)
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.
Measured: 6 weeks
Sleep-related quality of life: Functional Outcome of Sleep Questionnaire (FOSQ-10)
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.
Measured: 6 weeks
Snoring intensity: Visual Analogue Scale (VAS)
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).
Measured: 6 weeks
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted27 Jan 2021
- Study start20 Apr 2021
- Primary completion19 Mar 2024
- Study completion5 May 2024
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for Obstructive Sleep ApneaStudies of the same condition, open and under way.
- More trials run by University Hospital, AntwerpThe sponsor's other registered studies.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase 4
- Primary purpose
- Treatment
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Masking
- Double blind
- Who is masked
- Participant, Care provider
- Enrolment
- 91 participants (actual)
Sponsor and investigators
- Lead sponsor
- University Hospital, Antwerp
- Sponsor type
- University, hospital or other
- Responsible party
- Sponsor
- Investigators
- Olivier Vanderveken, MD, PhD, Principal investigator, University Hospital, Antwerp
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT04726982
- Sponsor's protocol ID
- B3002021000015
- Status last verified
- Sep 2025
- First submitted
- 26 Jan 2021
- Last updated
- 24 Sep 2025
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- No
Study at a glance
From the registry record, last updated by the sponsor on 24 Sep 2025. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Optimal Dosage of Acetazolamide for Obstructive Sleep Apnea Treatment: a Parallel-group, Double-blind, Placebo-controlled, Randomized Trial
- ClinicalTrials.gov ID
- NCT04726982
- Acronym / sponsor ID
- B3002021000015
- Conditions
- Obstructive Sleep Apnea
- Keywords
- Carbonic anhydrase inhibitor, Treatment, Pharmacotherapy, Sleep apnea, Loop gain, Respiration, Ventilatory control instability, Acidosis
- Phase
- Phase 4
- Study type
- Interventional
- Recruitment status
- Completed
- Enrolment
- 91 participants (actual)
- Lead sponsor
- University Hospital, AntwerpUniversity, hospital or other
- Study start
- 20 Apr 2021 (actual)
- Primary completion
- 19 Mar 2024 (actual)
- Study completion
- 5 May 2024 (actual)
- First posted
- 27 Jan 2021 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
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.
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 design
- Primary purpose
- Treatment
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Masking
- Double blind (participant, care provider)
- Number of arms
- 3
| Arm | Type | Receives |
|---|---|---|
| Low dose acetazolamide | Experimental | Drug: AcetazolamideUnembellished white tablets. The drug should be taken one hour before bedtime. Total treatment duration will be 6 weeks. |
| High dose acetazolamide | Experimental | Drug: AcetazolamideUnembellished white tablets. The drug should be taken one hour before bedtime. Total treatment duration will be 6 weeks. |
| Placebo | Placebo comparator | Other: PlaceboMatching placebo tablets. The drug should be taken one hour before bedtime. Total treatment duration will be 6 weeks. |
Who may qualify
- Ages
- 18 to 79 years
- Sex
- All
- Healthy volunteers
- Not accepted
- Age groups
- Adult, Older adult
Key inclusion criteria (2 listed)
- AHI between 15 and 65 events/hour
- BMI < 35 kg/m²
Key exclusion criteria (14 listed)
- Craniofacial anomalies
- Central sleep apnea (defined as central AHI > 25% of total AHI)
- Contra-indications related to acetazolamide treatment
- 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
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| AcetazolamideAlso: Diamox, ATC code: S01EC01250 mg once daily | Drug | Low dose acetazolamide |
| AcetazolamideAlso: Diamox, ATC code: S01EC01500 mg once daily | Drug | High dose acetazolamide |
| PlaceboOnce daily | Other | Placebo |
Primary outcome
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).
9 secondary outcomes
Pathophysiological traits
Time frame: 4 weeks
Percent responders
Time frame: 4 weeks
Nocturnal oxygen saturation
Time frame: 4 weeks
Oxygen desaturation index (ODI)
Time frame: 4 weeks
Arterial blood gas measurements
Time frame: 4 weeks
Lung function parameters
Time frame: 4 weeks
Daytime sleepiness: Epworth Sleepiness Scale (ESS)
Time frame: 6 weeks
Sleep-related quality of life: Functional Outcome of Sleep Questionnaire (FOSQ-10)
Time frame: 6 weeks
Snoring intensity: Visual Analogue Scale (VAS)
Time frame: 6 weeks
Results and safety
The study is completed, but results are not available in the source record. That does not mean the treatment did or did not work.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 24 Sep 2025.
- Individual participant dataSharing planned: No
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part. This study is not recruiting at the moment.
Olivier Vanderveken, MD, PhD principal investigator
University Hospital, Antwerp
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A Phase 4 study testing Acetazolamide in people with Obstructive Sleep Apnea, run by University Hospital, Antwerp at 1 site in Belgium.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 2 inclusion and 14 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: finished, as of the sponsor's last update on 24 Sep 2025. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 1 site in Belgium. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. Some participants in this study may receive a placebo. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
What does this phase mean?
Phase 4 studies take place after a treatment is approved, to learn more about its long-term benefits and risks in everyday use.
Not every study follows the same path, and some studies (observational studies, device studies) have no phase.
Are results available for this study?
The study is completed, but results are not available in the source record. That does not mean the treatment did or did not work.
How can a doctor refer a patient or contact the research team?
The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Apnea-hypopnea index (AHI) (time frame: 4 weeks). It is what the study was designed to measure, not a finding.
Where can I read the original study information?
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 24 Sep 2025.