Is it safe for me, with recent heart disease and current cardiac medications, to take the travel clinic‑prescribed altitude‑prophylaxis drug (acetazolamide) for an 8,000‑ft hike in Tanzania, and what precautions should I observe, especially regarding my new knee problems?

Acetazolamide Safety with Recent Heart Disease

Yes, you can safely take acetazolamide for your 8,000-foot Tanzania hike, but you must continue all your current cardiac medications and be aware of specific precautions regarding diuretic interactions and dehydration risk. 1

Key Safety Considerations

Medication Continuation

• All cardiovascular patients should continue their pre-existing medications at high altitude without interruption. 1 This is a Class I recommendation from the European Society of Cardiology, meaning it is the strongest level of guidance available.
• Any changes to your cardiac medications, particularly if you're on dual antiplatelet therapy after stent placement, must be discussed with your cardiologist before your trip. 1

Acetazolamide-Specific Precautions

Critical Drug Interaction Warning:

• The concomitant administration of acetazolamide with other diuretics may increase the risk of dehydration and electrolyte imbalances at high altitude and requires careful evaluation. 1 If you're taking any diuretic medications (furosemide, hydrochlorothiazide, spironolactone, etc.), this is your primary concern.
• Monitor for signs of dehydration: increased thirst, decreased urine output, dizziness, or lightheadedness. 1

Potential Benefits for Cardiac Patients:

• Acetazolamide may actually reduce the risk of subendocardial ischemia at high altitude in healthy subjects, suggesting it might be helpful for patients with coronary artery disease, though data in cardiac patients specifically is limited. 1

Altitude-Specific Cardiac Recommendations

Your 8,000-foot (approximately 2,400 meters) destination falls into the "intermediate altitude" category:

• If you have stable heart failure (NYHA Class I-II), you may safely reach altitudes up to 3,500 meters with not heavier than moderate physical activity. 1
• If you have stable NYHA Class III heart failure, you may reach up to 3,000 meters with only light physical activity. 1
• Given your recent difficulty acclimating at 10,000-11,000 feet, plan for gradual ascent and limit physical exertion during the first 24-48 hours. 1

Beta-Blocker Considerations

• If you're taking beta-blockers (common after heart disease), be aware that non-cardioselective beta-blockers (like carvedilol) may reduce your ability to adapt to altitude by decreasing peak exercise ventilation and oxygen uptake. 1
• Cardioselective beta-1 blockers (like metoprolol, bisoprolol, or nebivolol) are preferred for high-altitude exposure. 1

Acetazolamide Dosing

Standard prophylactic dosing is 125-250 mg twice daily, starting 1-2 days before ascent: 2, 3

• The 250 mg twice daily dose has been shown more effective than 125 mg twice daily at moderate altitudes (around 3,630 meters). 4
• Given your previous difficulty acclimating, the higher dose (250 mg twice daily) would be more appropriate. 4
• Acetazolamide reduces acute mountain sickness risk by approximately 48% compared to placebo. 3

Monitoring and Warning Signs

Seek immediate medical attention or descend if you experience:

• Chest pain, pressure, or discomfort
• Severe shortness of breath at rest
• Irregular heartbeat or palpitations
• Severe dizziness or lightheadedness (possible dehydration or electrolyte imbalance)
• Signs of severe altitude illness: severe headache unrelieved by medication, confusion, difficulty walking, or persistent vomiting 2

Practical Recommendations

Hydration Strategy:

• Maintain aggressive hydration to counteract both altitude-induced diuresis and acetazolamide's mild diuretic effect. 1
• Monitor urine color (should be pale yellow) as a hydration marker.

Ascent Planning:

• Use slow, gradual ascent (not exceeding 300-500 meters per day when above 2,500 meters). 1
• Plan rest days during your trek to allow acclimatization.

Physical Activity:

• Avoid intense physical exertion during the first 24-48 hours at altitude. 1
• Given your recent heart history, limit yourself to light-to-moderate activity even after acclimatization. 1

Regarding Your Knee Problems

Your new knee issues are a separate concern but relevant for high-altitude trekking:

• Ensure you have adequate pain management that doesn't interact with your cardiac medications.
• NSAIDs (commonly used for knee pain) can cause fluid retention and may interfere with some cardiac medications—discuss alternatives with your doctor before departure.
• Consider trekking poles to reduce knee stress during descent, which is typically harder on knees than ascent.

Common Pitfalls to Avoid

• Do not stop or reduce your cardiac medications thinking they might interfere with altitude adaptation. 1
• Do not ignore early symptoms of altitude illness (headache, nausea, fatigue), hoping they will resolve—acetazolamide works best when started before symptoms develop. 2
• Do not assume that because 8,000 feet is lower than where you had trouble before, you won't need precautions—individual susceptibility varies, and your recent difficulty suggests you're more susceptible. 2
• Do not combine acetazolamide with high-dose aspirin without medical supervision, as this combination has been associated with serious adverse effects including lethargy and metabolic acidosis. 5