HighCycle Study: Acetazolamide, High Altitude and Plasma Volume

NCT ID: NCT07118462

Last Updated: 2025-08-12

Basic Information

• Recruitment Status: RECRUITING
• Clinical Phase: PHASE4
• Total Enrollment: 270 participants
• Study Classification: INTERVENTIONAL
• Study Start Date: 2024-07-15
• Study Completion Date: 2025-12-31

Brief Summary

Each year, millions of people living at low altitude (< 1,000 m) travel to high altitude (≥ 2,500 m) for work, tourism, or sports activities. These individuals are exposed to hypobaric hypoxia, which can trigger acute mountain sickness (AMS)-the most common form of altitude-related illness. Therefore, understanding the physiological responses to hypoxia that allow acclimatization, as well as the pathophysiology of acute mountain sickness, is of primary importance.

The hematological response to high-altitude exposure initially includes a reduction in plasma volume (PV), leading to an early increase in hemoglobin concentration within the first 24 hours. In contrast, an increase in hemoglobin mass requires several weeks at high altitude. Recent well-controlled physiological studies conducted in hypobaric chambers have demonstrated that this hypoxia-induced PV contraction results from fluid redistribution from the intravascular to the extravascular compartment, rather than from water loss due to increased diuresis.

Prophylaxis of AMS is primarily based on the administration of 250 mg/day of acetazolamide (ACZ), a carbonic anhydrase inhibitor with a mild diuretic effect. Acetazolamide induces metabolic acidosis, which stimulates ventilation and thereby improves oxygenation. The effect of prophylactic ACZ use during high-altitude exposure on PV in lowlanders remains unknown: it is unclear whether ACZ leads to a greater reduction in PV due to its diuretic effect, or to a smaller hypoxia-induced PV contraction as a result of improved oxygenation induced by increased ventilation.

Detailed Description

Not provided

Conditions

High Altitude Effects; High Altitude Hypoxia; Acute Mountain Sickness (AMS); Plasma Volume; Women

Study Design

• Allocation Method: RANDOMIZED
• Intervention Model: PARALLEL
• Primary Study Purpose: BASIC_SCIENCE
• Blinding Strategy: QUADRUPLE

Study Groups

Acetazolamide

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

Group Type: EXPERIMENTAL

Acetazolamide

Intervention Type: DRUG

Administration of 1x125mg acetazolamide in the morning, 1x125mg in the evening, starting 24 hours before departure to 3600 m.

Placebo

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.

Group Type: PLACEBO_COMPARATOR

Placebo

Intervention Type: DRUG

Administration of equally looking placebo capsules in the morning and in the evening, starting 24 hours before departure to 3600 m.

Interventions

Acetazolamide

Administration of 1x125mg acetazolamide in the morning, 1x125mg in the evening, starting 24 hours before departure to 3600 m.

Intervention Type: DRUG

Placebo

Administration of equally looking placebo capsules in the morning and in the evening, starting 24 hours before departure to 3600 m.

Intervention Type: DRUG

Other Intervention Names

Diamox®

Eligibility Criteria

Inclusion Criteria

• Healthy, non-smoking men and women, age 18-44 years, without any disease 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 (contraceptives (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.

• Minimum Eligible Age: 18 Years
• Maximum Eligible Age: 44 Years
• Eligible Sex: ALL
• Accepts Healthy Volunteers: Yes

Sponsors

National Center of Cardiology and Internal Medicine named after academician M.Mirrakhimov

OTHER_GOV

Sponsor Role: collaborator

University of Zurich

OTHER

Sponsor Role: collaborator

Centre d'Expertise sur l'Altitude EXALT

OTHER

Sponsor Role: lead

Responsible Party

Responsibility Role: SPONSOR

Principal Investigators

Michael Furian, Prof. Dr.

Role: STUDY_CHAIR

University of Zurich

Talant M Sooronbaev, Prof. Dr.

Role: STUDY_DIRECTOR

National Center of Cardiology and Internal Medicine, Bishkek, Kyrgyzstan

Paul Robach, PhD

Role: PRINCIPAL_INVESTIGATOR

EXALT (Centre d'Expertise sur l'Altitude), Grenoble, France

Benoit Champigneulle, MD, PhD

Role: PRINCIPAL_INVESTIGATOR

EXALT (Centre d'Expertise sur l'Altitude), Grenoble, France

Locations

National Center for Cardiology and Internal Medicine

Bishkek, , Kyrgyzstan

Site Status: RECRUITING

Countries

Kyrgyzstan

Central Contacts

Benoit Champigneulle, MD PhD

Role: CONTACT

BChampigneulle@chu-grenoble.fr

+33476769288

Paul Robach, PhD

Role: CONTACT

paul.robach@ensm.sports.gouv.fr

+33667053919

Facility Contacts

Talant M Sooronbaev, Prof. Dr.

Role: primary

sooronbaev@yahoo.com

+996 312 625679

Other Identifiers

HighCycle_PV

Identifier Type: -

Identifier Source: org_study_id