Overview
Midodrine hydrochloride is an alpha-1 adrenergic agonist indicated for symptomatic orthostatic hypotension. It increases standing systolic blood pressure through peripheral vasoconstriction but carries a risk of supine hypertension. Treatment should be reserved for patients with significant impairment despite non-pharmacologic measures.
Mechanism of Action
Midodrine is a prodrug converted to its active metabolite desglymidodrine, which acts as a selective alpha-1 adrenergic receptor agonist. This causes peripheral vasoconstriction through arterial and venous constriction, increasing vascular resistance and blood pressure.
Indications
- Symptomatic orthostatic hypotension
Common Doses
- 2.5 mg
- 5 mg
- 10 mg
Dosage
Recommended dose is 10 mg three times daily during waking hours (approximately 4-hour intervals), with last dose no later than 6 PM. Dosing should be individualized based on symptomatic response and blood pressure monitoring, with caution in renal impairment.
Contraindications
- Severe organic heart disease
- Acute renal disease
- Urinary retention
- Pheochromocytoma
- Thyrotoxicosis
- Persistent and excessive supine hypertension
Side Effects
- Supine and sitting hypertension
- Paresthesia (especially scalp)
- Pruritus (especially scalp)
- Piloerection (goosebumps)
- Chills
- Urinary urgency/retention/frequency
- Headache
- Facial flushing
- Dry mouth
- Nervousness/anxiety
Interactions
- Avoid concomitant use with other blood pressure increasing drugs (phenylephrine, pseudoephedrine, ephedrine)
- Cardiac glycosides may enhance bradycardia/arrhythmias
- Alpha-blockers (prazosin, terazosin, doxazosin) antagonize effects
- MAO inhibitors and linezolid should be avoided
- Monitor carefully with fludrocortisone and salt supplementation
Counseling Points
- Take during waking hours only, with last dose before 6 PM
- Monitor blood pressure regularly in supine and standing positions
- Report symptoms of supine hypertension (headache, blurred vision)
- Be aware of pilomotor reactions (goosebumps, scalp tingling)
- Avoid lying flat for prolonged periods after dosing
- Report urinary symptoms or retention