midodrine hydrochloride

midodrine hydrochloride

Amatine (CA), ProAmatine

Pharmacologic class: Alpha₁-adrenergic agonist

Therapeutic class: Antihypotensive, vasopressor

Pregnancy risk category C

FDA Boxed Warning

• Drug can markedly increase supine blood pressure, and should be used in patients whose lives are considerably impaired despite standard clinical care. Indication for its use in treating symptomatic orthostatic hypotension rests mainly on an increase in systolic pressure measured 1 minute after standing. Currently, drug's clinical benefits (mainly improved ability to perform activities of daily living) haven't been verified.

Action

Forms active metabolite, desglymidodrine, an alpha₁-adrenergic agonist that activates alpha-adrenergic receptors in arteriolar and venous vasculature. This effect increases vascular resistance and ultimately raises blood pressure.

Availability

Tablets: 2.5 mg, 5 mg

⊘Indications and dosages

➣ Symptomatic orthostatic hypotension

Adults: 10 mg P.O. t.i.d. during daytime hours with patient in upright position. Give first dose when patient arises in morning, second dose at midday, and third dose in late afternoon.

Dosage adjustment

• Renal impairment

Contraindications

• Severe coronary artery disease or organic heart disease
• Acute renal disease, urinary retention
• Pheochromocytoma
• Thyrotoxicosis
• Persistent, excessive supine hypertension

Precautions

Use cautiously in:
• renal or hepatic impairment, diabetes mellitus, vision problems
• pregnant or breastfeeding patients.

Administration

• Don't give within 4 hours of bedtime.

Route	Onset	Peak	Duration
P.O.	Rapid	1-2 hr	Unknown

Adverse reactions

CNS: paresthesia

CV: vasodilation, bradycardia, supine hypertension

GI: abdominal pain, dry mouth

GU: urinary retention, frequency, or urgency

Skin: rash, pruritus, piloerection

Other: chills, increased pain

Interactions

Drug-drug. Alpha- and beta-adrenergic blockers, cardiac glycosides, steroids: increased risk of bradycardia, atrioventricular block

Alpha-adrenergic blockers, fludrocortisone: increased risk of supine hypertension

Patient monitoring

• Monitor supine and sitting blood pressures closely. Report marked rise in supine blood pressure.
• Stay alert for paresthesias.
• Monitor kidney function studies and fluid intake and output. Watch for urinary frequency, urgency, or retention.

Patient teaching

☞ Instruct patient to take while in upright position.
• Tell patient to take first dose as soon as he arises for the day, second dose at midday, and third dose in late afternoon (before 6 P.M.). Stress that doses must be taken at least 3 hours apart. Advise patient not to take drug after dinner or within 4 hours of bedtime.
☞ Instruct patient to promptly report symptoms of supine hypertension (pounding in ears, blurred vision, headache).
• Caution patient to avoid driving and other hazardous activities until he knows how drug affects concentration, vision, and alertness.
• As appropriate, review all other significant and life-threatening adverse reactions and interactions, especially those related to the drugs mentioned above.