HighCycle Study: Effect of Acetazolamide on Acute Mountain Sickness in Women Compared to Men

NCT ID: NCT06499727

Last Updated: 2026-01-23

Basic Information

• Recruitment Status: COMPLETED
• Clinical Phase: PHASE4
• Total Enrollment: 303 participants
• Study Classification: INTERVENTIONAL
• Study Start Date: 2024-07-15
• Study Completion Date: 2025-08-31

Brief Summary

Millions of people travel to high altitude for work or leisure activities and are exposed to reduced inspiratory oxygen partial pressure and hypoxemia that may lead to altitude illness, among which the most common form is acute mountain sickness (AMS). The main AMS symptoms are headache, malaise, weakness, and fatigue. Prospective studies have shown that 20-60% of newcomers at 2500-4000m develop AMS requiring them to take medications, while, at very high altitudes, AMS may progress to high altitude cerebral oedema. Whether women are more susceptible to AMS remains insufficiently understood since no prospective study controlled for sex hormones, use of hormone contraception or assessed menstrual cycle phase (MCP) at altitude. Therefore, women remain underrepresented and poorly characterized in high altitude studies. In addition, the efficacy and safety of 250 mg/day acetazolamide, the standard recommendation for AMS prevention, has never been compared between sexes, although, women have presumably higher acetazolamide plasma concentration due to lower blood volume. Given the known dose-dependent preventive but also side effects of acetazolamide and equal proportion of women and men among mountain travellers, there is an urgent need to conclusively quantify the efficacy and safety of pre-ventive acetazolamide therapy against AMS in women compared to men.

Conditions

Acute Mountain Sickness

Study Design

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

Study Groups

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.

Group Type: ACTIVE_COMPARATOR

Acetazolamide

Intervention Type: DRUG

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

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.

Group Type: ACTIVE_COMPARATOR

Acetazolamide

Intervention Type: DRUG

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

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.

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.

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.

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

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 Hospital Heidelberg

OTHER

Sponsor Role: collaborator

Laboratoire des Adaptations Métaboliques à l'Exercice en conditions Physiologiques et Pathologiques

OTHER

Sponsor Role: collaborator

University of Zurich

OTHER

Sponsor Role: lead

Responsible Party

Responsibility Role: SPONSOR

Principal Investigators

Michael Furian, Prof. Dr.

Role: STUDY_CHAIR

University of Zurich

Talant Sooronbaev, Prof. Dr.

Role: STUDY_DIRECTOR

National Center of Cardiology and Internal Medicine, Bishkek, Kyrgyzstan

Locations

National Center for Cardiology and Internal Medicine

Bishkek, Gorod Bishkek, Kyrgyzstan

Countries

Kyrgyzstan

Other Identifiers

HighCycle_AMS

Identifier Type: -

Identifier Source: org_study_id