Midodrine Administration Parameters for Blood Oxygen and Heart Rate
Midodrine should be administered with caution regarding heart rate, with no specific blood oxygen parameters required, but should be avoided in patients with bradycardia, as it may cause reflex parasympathetic stimulation. 1
Dosing Recommendations
- Initial dose of 2.5-5 mg three times daily, with the first dose taken before arising and the last dose at least 4 hours before bedtime to avoid supine hypertension 1, 2
- Dose can be titrated up to 10 mg three times daily based on symptomatic response and blood pressure measurements 1, 3
- Peak effect occurs approximately 1 hour after administration, with effects lasting 2-3 hours 2, 3
- For dialysis patients, a single 5 mg dose can be administered 30 minutes before dialysis to prevent intradialytic hypotension 1
Heart Rate Considerations
- Monitor for bradycardia, as midodrine is associated with reflex parasympathetic stimulation 1, 2
- Use with caution in patients with congestive heart failure or those taking negative chronotropic agents (beta-blockers, digoxin, non-dihydropyridine calcium channel blockers) 1
- No specific heart rate cutoff is established in guidelines, but caution is warranted in patients with pre-existing bradycardia 1
Blood Pressure Parameters
- Midodrine increases standing systolic blood pressure by approximately 15-30 mmHg at 1 hour after a 10 mg dose 2, 4
- Monitor for supine hypertension, which occurs in up to 10% of patients on long-term therapy 1, 5
- Discontinue therapy if supine systolic hypertension exceeds 180 mmHg or diastolic exceeds 110 mmHg 1, 6
Important Precautions
- Avoid concomitant use with other alpha-adrenergic agents (ephedrine, pseudoephedrine, phenylpropanolamine) as this may aggravate supine hypertension 1, 7
- May antagonize the actions of alpha-adrenergic blockers (terazosin, prazosin, doxazosin) and could result in urinary retention 1
- Common side effects include piloerection, scalp itching/tingling, nausea, urinary urgency, and chills 7, 5
Clinical Pearls
- Midodrine is a prodrug that is converted to desglymidodrine, the active alpha-1 agonist 2, 7
- Desglymidodrine has poor penetration across the blood-brain barrier, resulting in minimal central nervous system effects 2
- In dialysis patients, midodrine is effectively cleared by hemodialysis with a reduced half-life of 1.4 hours 1
- The combination of cool dialysate and predialysis doses of midodrine may provide better management of intradialytic hypotension with fewer side effects 1