What are the parameters for holding midodrine (ProAmatine) in patients with orthostatic hypotension?

Parameters for Holding Midodrine in Orthostatic Hypotension

Midodrine should be held if the patient has supine systolic blood pressure ≥200 mmHg or if the patient will be supine for an extended period of time. 1

Key Parameters for Holding Midodrine

Supine Hypertension

• Hold midodrine if supine systolic blood pressure ≥200 mmHg 1
• Supine hypertension occurs in up to 25% of patients on midodrine therapy 2
• The risk of supine hypertension should be evaluated at the beginning of midodrine therapy 1

Timing Considerations

• The last daily dose should be taken 3-4 hours before bedtime to minimize nighttime supine hypertension 1, 3
• Patients should avoid taking midodrine if they will be supine for any length of time 1
• Midodrine should not be taken later than 6 PM 4, 1

Bradycardia

• Hold midodrine if the patient experiences signs or symptoms of bradycardia:
  • Pulse slowing
  • Increased dizziness
  • Syncope
  • Cardiac awareness 1

Urinary Retention

• Hold midodrine in patients experiencing urinary retention, as desglymidodrine acts on the alpha-adrenergic receptors of the bladder neck 1

Monitoring Parameters

Blood Pressure Monitoring

• Monitor both standing and supine blood pressure regularly
• Standing blood pressure typically increases by 15-30 mmHg at 1 hour after a 10 mg dose 1
• Effects may persist for 2-3 hours after dosing 1

Heart Rate

• Monitor for bradycardia, especially in patients taking other medications that reduce heart rate 1
• Midodrine can cause reflex parasympathetic stimulation leading to bradycardia 4

Special Considerations

Concomitant Medications

• Use caution when midodrine is used with:
  • Cardiac glycosides (e.g., digitalis) - may enhance bradycardia 1
  • Beta blockers - may enhance bradycardia 1
  • Other agents that reduce heart rate 1
  • Other vasoconstrictors (e.g., phenylephrine, ephedrine) - may enhance hypertension 1
  • MAO inhibitors or linezolid - avoid concomitant use 1
  • Alpha-adrenergic blockers (e.g., prazosin, terazosin) - can antagonize midodrine effects 1

Renal Impairment

• Use with caution in patients with renal impairment as desglymidodrine is eliminated via the kidneys 1
• Consider starting at a lower dose (2.5 mg) in patients with renal impairment 1

Hepatic Impairment

• Use with caution in patients with hepatic impairment as the liver has a role in midodrine metabolism 1

Clinical Pearls

• Midodrine is effectively cleared by hemodialysis, with its half-life reduced to 1.4 hours during dialysis 4
• The active metabolite (desglymidodrine) has a half-life of approximately 3-4 hours 1, 5
• The optimal dosing for most patients is 10 mg taken 2-3 times daily 5
• Patients should be instructed to report symptoms of supine hypertension immediately (cardiac awareness, pounding in ears, headache, blurred vision) 1

By following these parameters for holding midodrine, clinicians can maximize the benefits of this medication while minimizing the risks of adverse effects in patients with orthostatic hypotension.