Midodrine Dosing Parameters for Orthostatic Hypotension
Midodrine should be dosed at 5-20mg three times daily, with the last dose taken at least 4 hours before bedtime to avoid supine hypertension. 1, 2
Dosing Regimen
- Starting dose: 2.5-5mg three times daily
- Titration: Increase by 2.5mg increments weekly as tolerated
- Target dose: 10mg three times daily (most effective standard dose)
- Maximum dose: 20mg three times daily
- Timing: Doses should be taken approximately 3-4 hours apart
- Last dose timing: Must be taken at least 4 hours before bedtime to minimize risk of supine hypertension
Pharmacokinetics
- Midodrine is a prodrug that is metabolized to desglymidodrine (active metabolite)
- Peak plasma levels of midodrine occur at 30 minutes
- Peak effect of desglymidodrine occurs 1-2 hours after administration
- Duration of action: 2-3 hours for 10mg dose, up to 4 hours for 20mg dose
- Half-life of desglymidodrine: 3-4 hours 2
- Bioavailability: 93% (not affected by food) 2
Monitoring Parameters
- Blood pressure: Check BP in both supine and standing positions
- Standing systolic BP typically increases by 15-30 mmHg at 1 hour post-dose
- Effect persists for 2-3 hours after 10mg dose 2
- Symptoms: Monitor for improvement in orthostatic symptoms (dizziness, lightheadedness, syncope)
- Supine hypertension: Monitor for BP >180/110 mmHg when supine (occurs in up to 25% of patients) 2, 3
- Urinary function: Watch for urinary retention
Efficacy Assessment
- Continue therapy only if patient reports significant symptomatic improvement 2
- Evaluate treatment efficacy based on symptom improvement rather than absolute BP values 1
- Improvement in standing time and energy levels should be noted 3
Contraindications and Precautions
Absolute contraindications:
- Severe organic heart disease
- Acute renal disease
- Urinary retention
- Pheochromocytoma
- Thyrotoxicosis
Relative contraindications:
Common Side Effects
- Piloerection (goosebumps): most common (13.5%)
- Pruritus/scalp tingling
- Paresthesias
- Urinary retention or urgency
- Chills
- Supine hypertension (up to 25% of patients) 3, 4
Special Populations
- Elderly patients: Higher risk of orthostatic hypotension (20% prevalence); require slower titration and close monitoring for falls 1
- Cardiac disease patients: Monitor closely for supine hypertension 1
- Diabetic patients with autonomic neuropathy: May require additional interventions 1
- Hemodialysis patients: Midodrine is removed by dialysis; dosing may need adjustment 2
Common Pitfalls to Avoid
- Administering the last dose too close to bedtime (increases risk of supine hypertension)
- Focusing on BP numbers rather than symptom improvement
- Overlooking non-pharmacological measures (which should be used concurrently)
- Inadequate monitoring for supine hypertension 1
Non-Pharmacological Adjuncts (to be used concurrently)
- Increased salt intake (6-10g daily)
- Physical counter-pressure maneuvers
- Compression garments (30-40 mmHg pressure)
- Small, frequent meals
- Acute water ingestion (500ml, 30 minutes before anticipated orthostatic stress) 1