Midodrine Hydrochloride

Midodrine hydrochloride tablets, USP are indicated for the treatment of symptomatic orthostatic hypotension (OH). Because midodrine hydrochloride tablets, USP 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 hydrochloride tablets, USP 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, USP 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, USP. After initiation of treatment, midodrine hydrochloride tablets, USP should be continued only for patients who report significant symptomatic improvement.

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

Because midodrine hydrochloride can cause marked elevation of supine blood pressure, it should be used in patients whose lives are considerably impaired despite standard clinical care. The indication for use of midodrine hydrochloride in the treatment of symptomatic orthostatic hypotension is based primarily on a change in a surrogate marker of effectiveness, an increase in systolic blood pressure measured one minute after standing, a surrogate marker considered likely to correspond to a clinical benefit. At present, however, clinical benefits of midodrine hydrochloride, principally improved ability to carry out activities of daily living, have not been verified.

WARNINGS Supine Hypertension: The most potentially serious adverse reaction associated with midodrine hydrochloride 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 hydrochloride. 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 hydrochloride in such patients is not recommended. Sitting blood pressures were also elevated by midodrine hydrochloride therapy. It is essential to monitor supine and sitting blood pressures in patients maintained on midodrine hydrochloride. Uncontrolled hypertension increases the risk of cardiovascular events, particularly stroke.

General: The potential for supine and sitting hypertension should be evaluated at the beginning of midodrine hydrochloride therapy. Supine hypertension can often be controlled by preventing the patient from becoming fully supine, i.e., sleeping with the head of the bed elevated. The patient should be cautioned to report symptoms of supine hypertension immediately. Symptoms may include cardiac awareness, pounding in the ears, headache, blurred vision, etc. The patient should be advised to discontinue the medication immediately if supine hypertension persists. Blood pressure should be monitored carefully when midodrine hydrochloride is used concomitantly with other agents that cause vasoconstriction, such as phenylephrine, ephedrine, dihydroergotamine, phenylpropanolamine, or pseudoephedrine. A slight slowing of the heart rate may occur after administration of midodrine hydrochloride, primarily due to vagal reflex. Caution should be exercised when midodrine hydrochloride is used concomitantly with cardiac glycosides (such as digitalis), psychopharmacologic agents, beta blockers or other agents that directly or indirectly reduce heart rate. Patients who experience any signs or symptoms suggesting bradycardia (pulse slowing, increased dizziness, syncope, cardiac awareness) should be advised to discontinue midodrine hydrochloride and should be re-evaluated. Midodrine hydrochloride should be used cautiously in patients with urinary retention problems, as desglymidodrine acts on the alpha-adrenergic receptors of the bladder neck. Midodrine hydrochloride should be used with caution in orthostatic hypotensive patients who are also diabetic, as well as those with a history of visual problems who are also taking fludrocortisone acetate, which is known to cause an increase in intraocular pressure and glaucoma. Midodrine hydrochloride use has not been studied in patients with renal impairment. Because desglymidodrine is eliminated via the kidneys, and higher blood levels would be expected in such patients, midodrine hydrochloride should be used with caution in patients with renal impairment, with a starting dose of 2.5 mg ( See DOSAGE AND ADMINISTRATION). Renal function should be assessed prior to initial use of midodrine hydrochloride. Midodrine hydrochloride use has not been studied in patients with hepatic impairment. Midodrine hydrochloride should be used with caution in patients with hepatic impairment, as the liver has a role in the metabolism of midodrine. Information for Patients: Patients should be told that certain agents in over-the-counter products, such as cold remedies and diet aids, can elevate blood pressure, and therefore, should be used cautiously with midodrine hydrochloride, as they may enhance or potentiate the pressor effects of midodrine hydrochloride ( see Drug Interactions) . Patients should also be made aware of the possibility of supine hypertension. They should be told to avoid taking their dose if they are to be supine for any length of time, i.e., they should take their last daily dose of midodrine hydrochloride 3 to 4 hours before bedtime to minimize nighttime supine hypertension. Laboratory Tests: Since desglymidodrine is eliminated by the kidneys and the liver has a role in its metabolism, evaluation of the patient should include assessment of renal and hepatic function prior to initiating therapy and subsequently, as appropriate. Drug Interactions: When administered concomitantly with midodrine hydrochloride, 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 hydrochloride 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 hydrochloride. Alpha-adrenergic blocking agents, such as prazosin, terazosin, and doxazosin, can antagonize the effects of midodrine hydrochloride. Potential for Drug Interaction: It appears possible, although there is no supporting experimental evidence, that the high renal clearance of desglymidodrine (a base) is due to active tubular secretion by the base-secreting system also responsible for the secretion of such drugs as metformin, cimetidine, ranitidine, procainamide, triamterene, flecainide, and quinidine. Thus there may be a potential for drug-drug interactions with these drugs. Carcinogenesis, Mutagenesis, Impairment of Fertility: Long-term studies have been conducted in rats and mice at dosages 3 to 4 times the maximum recommended daily human dose on a mg/m 2 basis, with no indication of carcinogenic effects related to midodrine hydrochloride. Studies investigating the mutagenic potential of midodrine hydrochloride revealed no evidence of mutagenicity. Other than the dominant lethal assay in male mice, where no impairment of fertility was observed, there have been no studies on the effects of midodrine hydrochloride on fertility. Pregnancy: Pregnancy Category C. Midodrine hydrochloride 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 hydrochloride 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. Nursing Mothers: It is not known whether this drug is excreted in human milk. Because many drugs are excreted in human milk, caution should be exercised when midodrine hydrochloride is administered to a nursing woman. Pediatric Use: Safety and effectiveness in pediatric patients have not been established.

Information for Patients: Patients should be told that certain agents in over-the-counter products, such as cold remedies and diet aids, can elevate blood pressure, and therefore, should be used cautiously with midodrine hydrochloride, as they may enhance or potentiate the pressor effects of midodrine hydrochloride ( see Drug Interactions) . Patients should also be made aware of the possibility of supine hypertension. They should be told to avoid taking their dose if they are to be supine for any length of time, i.e., they should take their last daily dose of midodrine hydrochloride 3 to 4 hours before bedtime to minimize nighttime supine hypertension.

Laboratory Tests: Since desglymidodrine is eliminated by the kidneys and the liver has a role in its metabolism, evaluation of the patient should include assessment of renal and hepatic function prior to initiating therapy and subsequently, as appropriate.

Potential for Drug Interaction: It appears possible, although there is no supporting experimental evidence, that the high renal clearance of desglymidodrine (a base) is due to active tubular secretion by the base-secreting system also responsible for the secretion of such drugs as metformin, cimetidine, ranitidine, procainamide, triamterene, flecainide, and quinidine. Thus there may be a potential for drug-drug interactions with these drugs.

The most frequent adverse reactions seen in controlled trials were supine and sitting hypertension; paresthesia and pruritus, mainly of the scalp; goosebumps; chills; urinary urge; urinary retention and urinary frequency. The frequency of these events in a 3-week placebo-controlled trial is shown in the following table: Adverse Events Placebo n = 88 Midodrine n = 82 Event # of reports % of patients # of reports % of patients Total # of reports 22 77 Paresthesia * 4 4.5 15

18.3 Piloerection 0 0 11

13.4 Dysuria † 0 0 11

13.4 Pruritus ‡ 2 2.3 10

12.2 Supine hypertension § 0 0 6

7.3 Chills 0 0 4

4.9 Pains ¶ 0 0 4

4.9 Rash 1 1.1 2 2.4 * Includes hyperesthesia and scalp paresthesia † Includes dysuria (1), increased urinary frequency (2), impaired urination (1), urinary retention (5), urinary urgency (2) ‡ Includes scalp pruritus § Includes patients who experienced an increase in supine hypertension ¶ Includes abdominal pain and pain increase Less frequent adverse reactions were headache; feeling of pressure/fullness in the head; vasodilation/flushing face; confusion/thinking abnormality; dry mouth; nervousness/anxiety and rash. Other adverse reactions that occurred rarely were visual field defect; dizziness; skin hyperesthesia; insomnia; somnolence; erythema multiforme; canker sore; dry skin; dysuria; impaired urination; asthenia; backache; pyrosis; nausea; gastrointestinal distress; flatulence and leg cramps. The most potentially serious adverse reaction associated with midodrine hydrochloride therapy is supine hypertension. The feelings of paresthesia, pruritus, piloerection and chills are pilomotor reactions associated with the action of midodrine on the alpha-adrenergic receptors of the hair follicles. Feelings of urinary urgency, retention and frequency are associated with the action of midodrine on the alpha-receptors of the bladder neck.

When administered concomitantly with midodrine hydrochloride, 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 hydrochloride 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 hydrochloride. Alpha-adrenergic blocking agents, such as prazosin, terazosin, and doxazosin, can antagonize the effects of midodrine hydrochloride.

Pregnancy Category C. Midodrine hydrochloride 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 hydrochloride 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.

It is not known whether this drug is excreted in human milk. Because many drugs are excreted in human milk, caution should be exercised when midodrine hydrochloride is administered to a nursing woman.

Safety and effectiveness in pediatric patients have not been established.

Midodrine hydrochloride forms an active metabolite, desglymidodrine, that is an alpha 1 -agonist, and exerts its actions via activation of the alpha-adrenergic receptors of the arteriolar and venous vasculature, producing an increase in vascular tone and elevation of blood pressure. Desglymidodrine does not stimulate cardiac beta-adrenergic receptors. Desglymidodrine diffuses poorly across the blood-brain barrier, and is therefore not associated with effects on the central nervous system. Administration of midodrine hydrochloride results in a rise in standing, sitting, and supine systolic and diastolic blood pressure in patients with orthostatic hypotension of various etiologies. Standing systolic blood pressure is elevated by approximately 15 to 30 mmHg at 1 hour after a 10 mg dose of midodrine, with some effect persisting for 2 to 3 hours. Midodrine hydrochloride has no clinically significant effect on standing or supine pulse rates in patients with autonomic failure.