Midodrine

DESCRIPTION Name: Midodrine hydrochloride tablets, USP Dosage Form: 2.5 mg, 5 mg and 10 mg tablets for oral administration Active Ingredient: Midodrine hydrochloride, USP 2.5 mg, 5 mg and 10 mg Inactive Ingredients: Microcrystalline cellulose, crospovidone, hydroxypropyl cellulose, colloidal silicon dioxide and magnesium stearate. Pharmacological Classification: Vasopressor/Antihypotensive Chemical Names (USAN: Midodrine Hydrochloride): (1) Acetamide, 2-amino- N -[2-(2,5-dimethoxyphenyl)-2-hydroxyethyl]-monohydrochloride, (±)-; (2) (±)-2-amino-N-(ß-hydroxy-2,5-dimethoxyphenethyl)acetamide monohydrochloride BAN, INN, JAN: Midodrine Structural Formula: Molecular Formula: C 12 H 18 N 2 O 4 HCl Molecular Weight: 290.7 Organoleptic Properties: Odorless, white to off-white powder Solubility: Soluble in water, sparingly soluble in methanol pKa: 7.8 (0.3% aqueous solution) pH: 3.5 to 5.5 (5% aqueous solution) Melting Range: 200 to 203°C structure

INDICATIONS AND USAGE Midodrine hydrochloride tablets are indicated for the treatment of symptomatic orthostatic hypotension (OH). Because midodrine hydrochloride tablets can cause marked elevation of supine blood pressure (BP>200 mmHg systolic), it should be used in patients whose lives are considerably impaired despite standard clinical care, including non-pharmacologic treatment (such as support stockings), fluid expansion, and lifestyle alterations. The indication is based on midodrine’s effect on increases in 1-minute standing systolic blood pressure, a surrogate marker considered likely to correspond to a clinical benefit. At present, however, clinical benefits of midodrine hydrochloride tablets, principally improved ability to perform life activities, have not been established. Further clinical trials are underway to verify and describe the clinical benefits of midodrine hydrochloride tablets. After initiation of treatment, midodrine hydrochloride tablets should be continued only for patients who report significant symptomatic improvement.

CONTRAINDICATIONS Midodrine hydrochloride tablets are contraindicated in patients with severe organic heart disease, acute renal disease, urinary retention, pheochromocytoma or thyrotoxicosis. Midodrine should not be used in patients with persistent and excessive supine hypertension.

WARNINGS Supine Hypertension: The most potentially serious adverse reaction associated with midodrine therapy is marked elevation of supine arterial blood pressure (supine hypertension). Systolic pressure of about 200 mmHg were seen overall in about 13.4% of patients given 10 mg of midodrine . Systolic elevations of this degree were most likely to be observed in patients with relatively elevated pre-treatment systolic blood pressures (mean 170 mmHg). There is no experience in patients with initial supine systolic pressure above 180 mmHg, as those patients were excluded from the clinical trials. Use of midodrine in such patients is not recommended. Sitting blood pressures were also elevated by midodrine therapy. It is essential to monitor supine and sitting blood pressures in patients maintained on midodrine . Uncontrolled hypertension increases the risk of cardiovascular events, particularly stroke.

Drug Interactions When administered concomitantly with midodrine, cardiac glycosides may enhance or precipitate bradycardia, A.V. block or arrhythmia. The risk of hypertension increases with concomitant administration of drugs that increase blood pressure (phenylephrine, pseudoephedrine, ephedrine, dihydroergotamine, thyroid hormones, or droxidopa). Avoid concomitant use of drugs that increase blood pressure. If concomitant use cannot be avoided, monitor blood pressure closely. Avoid use of MAO inhibitors or linezolid with midodrine. Midodrine has been used in patients concomitantly treated with salt-retaining steroid therapy (i.e., fludrocortisone acetate), with or without salt supplementation. The potential for supine hypertension should be carefully monitored in these patients and may be minimized by either reducing the dose of fludrocortisone acetate or decreasing the salt intake prior to initiation of treatment with midodrine. Alpha-adrenergic blocking agents, such as prazosin, terazosin, and doxazosin, can antagonize the effects of midodrine. Potential for Drug Interaction It appears possible, although there is no supporting experimental evidence, that the high renal clearance of desyglymidodrine (a base) is due to active tubular secretion by the base-secreting system also responsible for the secretionof such drugs as metformin, cimetidine, ranitidine, procainamide, triamterene, flecainide, and quinidine. Thus there may be a potential for drug-drug interactions with these drugs.

Pregnancy Midodrine increased the rate of embryo resorption, reduced fetal body weight in rats and rabbits, and decreased fetal survival in rabbits when given in doses 13 (rat) and 7 (rabbit) times the maximum human dose based on body surface area (mg/m 2 ). There are no adequate and well-controlled studies in pregnant women. Midodrine should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus. No teratogenic effects have been observed in studies in rats and rabbits.

Pediatric Use Safety and effectiveness in pediatric patients have not been established.

OVERDOSAGE Symptoms of overdose could include hypertension, piloerection (goosebumps), a sensation of coldness and urinary retention. There are 2 reported cases of overdosage with midodrine, both in young males. One patient ingested midodrine drops, 250 mg, experienced systolic blood pressure greater than 200 mmHg, was treated with an IV injection of 20 mg of phentolamine, and was discharged the same night without any complaints. The other patient ingested 205 mg of midodrine (41 5-mg tablets), and was found lethargic and unable to talk, unresponsive to voice but responsive to painful stimuli, hypertensive and bradycardic. Gastric lavage was performed, and the patient recovered fully by the next day without sequelae. The single doses that would be associated with symptoms of overdosage or would be potentially life-threatening are unknown. The oral LD 50 is approximately 30 to 50 mg/kg in rats, 675 mg/kg in mice, and 125 to 160 mg/kg in dogs. Desglymidodrine is dialyzable. Recommended general treatment, based on the pharmacology of the drug, includes induced emesis and administration of alpha-sympatholytic drugs (e.g., phentolamine).