At what level of hypotension should Midodrine be taken?

Midodrine for Orthostatic Hypotension: Blood Pressure Thresholds for Treatment

Midodrine should be administered when systolic blood pressure drops by ≥20 mmHg or diastolic blood pressure drops by ≥10 mmHg within 3 minutes of standing, accompanied by symptoms of orthostatic intolerance. 1

Diagnostic Criteria for Orthostatic Hypotension

Orthostatic hypotension (OH) requiring midodrine therapy is defined by:

• A decrease in systolic BP ≥20 mmHg or diastolic BP ≥10 mmHg within 3 minutes of standing
• Accompanied by symptoms such as:
  • Dizziness/lightheadedness
  • Visual disturbances
  • Weakness/fatigue
  • Low energy level
  • Syncope or near-syncope

Treatment Algorithm for Midodrine Use

Step 1: Confirm Orthostatic Hypotension

• Measure BP after 5 minutes of lying supine
• Measure BP at 1 and 3 minutes after standing
• Document associated symptoms

Step 2: Try Non-Pharmacological Approaches First

• Adequate hydration and salt intake (2-3 L fluids/day and 6-9g salt/day)
• Physical counterpressure maneuvers (leg crossing, squatting)
• Compression garments (thigh-high or abdominal)
• Elevation of head of bed by 10° during sleep
• Elimination of offending medications when possible

Step 3: Initiate Midodrine When Appropriate

• Starting dose: 2.5-5 mg three times daily
• Timing: First dose upon awakening, second dose at midday, last dose in late afternoon (at least 4 hours before bedtime)
• Maximum dose: 10 mg three times daily
• Dosing schedule: Approximately every 4 hours while awake (based on half-life)

Efficacy and Evidence

Midodrine has been shown to increase standing systolic blood pressure by approximately 22 mmHg (28%) at the 10 mg dose 2. Multiple randomized controlled trials demonstrate significant improvement in orthostatic symptoms including dizziness, weakness, syncope, and energy levels 2, 3, 4.

The European Society of Cardiology guidelines specifically recommend midodrine as a useful addition to first-line treatment in patients with chronic autonomic failure 1. Similarly, the Diabetes/Metabolism Research and Reviews guidelines identify midodrine as a first-line drug for symptomatic orthostatic hypotension 1.

Monitoring and Precautions

• Monitor for supine hypertension: Present in up to 8-25% of patients 2, 5
• Common side effects: Piloerection, scalp tingling/pruritus, urinary urgency
• Contraindications: Severe cardiac disease, acute renal disease, urinary retention, pheochromocytoma
• Drug interactions: Avoid concurrent use with other α-adrenergic agents and monitor closely if used with β-blockers

Special Populations

• Dialysis patients: Midodrine is effectively cleared by hemodialysis with reduced half-life (1.4 hours) 1
• Elderly: No specific dose adjustment needed, but monitor closely for supine hypertension
• Diabetes with autonomic neuropathy: May respond to lower doses (5 mg) 6

Important Caveats

1. The last daily dose should be taken at least 4 hours before bedtime to minimize risk of supine hypertension 5.
2. Midodrine increases BP in both supine and upright postures, so regular monitoring is essential 1.
3. Midodrine is not a cure for orthostatic hypotension but can significantly improve symptoms and quality of life 1.
4. For patients with vasovagal syncope, midodrine may be reasonable in those with recurrent episodes who have no history of hypertension, heart failure, or urinary retention 1.

By following this algorithm and carefully monitoring patients, midodrine can effectively manage orthostatic hypotension and improve quality of life in affected individuals.