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Mecamylamine

Pronunciation

(mek a MIL a meen)

Index Terms

  • Mecamylamine HCl
  • Mecamylamine Hydrochloride

Dosage Forms

Excipient information presented when available (limited, particularly for generics); consult specific product labeling. [DSC] = Discontinued product

Tablet, Oral, as hydrochloride:

Vecamyl: 2.5 mg

Brand Names: U.S.

  • Vecamyl

Pharmacologic Category

  • Ganglionic Blocking Agent

Pharmacology

Mecamylamine inhibits acetylcholine at the autonomic ganglia, causing a decrease in blood pressure. The blood pressure lowering effect is predominantly orthostatic; the supine blood pressure is also significantly decreased.

Absorption

Almost complete

Excretion

Urine (unchanged); rate of elimination is significantly affected by the pH of the urine. Acidic urine promotes excretion; alkalinization reduces excretion

Onset of Action

0.5 to 2 hours

Duration of Action

6 to ≥12 hours

Use: Labeled Indications

Hypertension: Management of moderately severe to severe essential hypertension and in uncomplicated malignant hypertension.

Use: Unlabeled

Tourette's syndrome

Contraindications

Hypersensitivity to mecamylamine or any component of the formulation; mild, moderate, labile hypertension (may not be suitable for uncooperative patients); coronary insufficiency or recent myocardial infarction; uremia; glaucoma; organic pyloric stenosis; coadministration with antibiotics or sulfonamides

Dosing: Adult

Hypertension: Oral: Initial: 2.5 mg twice daily; may increase by increments of 2.5 mg at intervals ≥2 days until desired blood pressure response is achieved; average dose: 25 mg/day (usually in 3 divided doses; range of 2 to 4 divided doses or more may be required). Note: A small dose and sometimes no dose at all, should be administered in the morning as the blood pressure response is heightened early in the day. The larger dose should be given at noontime or the evening.

Concomitant therapy: When coadministered with thiazide diuretics, decrease the dose of mecamylamine by ≥50%

Dosing: Geriatric

Refer to adult dosing.

Dosing: Renal Impairment

There are no dosage adjustments provided in the manufacturer's labeling; use with caution; use with extreme caution, if at all, if renal impairment is manifested by a rising or elevated BUN. Use is contraindicated in uremia.

Dosing: Hepatic Impairment

There are no dosage adjustments provided in the manufacturer's labeling

Administration

Administration after meals may cause a more gradual absorption and smoother control of excessively high blood pressure. Timing of relationship to meals should be consistent.

Dietary Considerations

Take after meals. Concomitant use of alcohol may potentiate the effects of mecamylamine.

Storage

Store at 20°C to 25°C (68°F to 77°F); excursions are permitted between 15°C and 30°C (59°F and 86°F)

Drug Interactions

Alcohol (Ethyl): May enhance the adverse/toxic effect of Mecamylamine. Monitor therapy

Alfuzosin: May enhance the hypotensive effect of Blood Pressure Lowering Agents. Monitor therapy

Alkalinizing Agents: May increase the serum concentration of Mecamylamine. Monitor therapy

Amifostine: Blood Pressure Lowering Agents may enhance the hypotensive effect of Amifostine. Management: When amifostine is used at chemotherapy doses, blood pressure lowering medications should be withheld for 24 hours prior to amifostine administration. If blood pressure lowering therapy cannot be withheld, amifostine should not be administered. Consider therapy modification

Aminoglycosides: May enhance the neuromuscular-blocking effect of Mecamylamine. Avoid combination

Amphetamines: May diminish the antihypertensive effect of Antihypertensive Agents. Monitor therapy

Antipsychotic Agents (Second Generation [Atypical]): Blood Pressure Lowering Agents may enhance the hypotensive effect of Antipsychotic Agents (Second Generation [Atypical]). Monitor therapy

Barbiturates: May enhance the hypotensive effect of Blood Pressure Lowering Agents. Monitor therapy

Benperidol: May enhance the hypotensive effect of Blood Pressure Lowering Agents. Monitor therapy

Brimonidine (Topical): May enhance the hypotensive effect of Blood Pressure Lowering Agents. Monitor therapy

Capreomycin: May enhance the neuromuscular-blocking effect of Mecamylamine. Avoid combination

Colistimethate: May enhance the neuromuscular-blocking effect of Mecamylamine. Avoid combination

Diazoxide: May enhance the hypotensive effect of Blood Pressure Lowering Agents. Monitor therapy

DULoxetine: Blood Pressure Lowering Agents may enhance the hypotensive effect of DULoxetine. Monitor therapy

Herbs (Hypertensive Properties): May diminish the antihypertensive effect of Antihypertensive Agents. Monitor therapy

Herbs (Hypotensive Properties): May enhance the hypotensive effect of Blood Pressure Lowering Agents. Monitor therapy

Hypotension-Associated Agents: Blood Pressure Lowering Agents may enhance the hypotensive effect of Hypotension-Associated Agents. Monitor therapy

Levodopa: Blood Pressure Lowering Agents may enhance the hypotensive effect of Levodopa. Monitor therapy

Lincosamide Antibiotics: May enhance the neuromuscular-blocking effect of Mecamylamine. Avoid combination

Lormetazepam: May enhance the hypotensive effect of Blood Pressure Lowering Agents. Monitor therapy

Methylphenidate: May diminish the antihypertensive effect of Antihypertensive Agents. Monitor therapy

Molsidomine: May enhance the hypotensive effect of Blood Pressure Lowering Agents. Monitor therapy

Naftopidil: May enhance the hypotensive effect of Blood Pressure Lowering Agents. Monitor therapy

Nicergoline: May enhance the hypotensive effect of Blood Pressure Lowering Agents. Monitor therapy

Nicorandil: May enhance the hypotensive effect of Blood Pressure Lowering Agents. Monitor therapy

Nitroprusside: Blood Pressure Lowering Agents may enhance the hypotensive effect of Nitroprusside. Monitor therapy

Obinutuzumab: May enhance the hypotensive effect of Blood Pressure Lowering Agents. Management: Consider temporarily withholding blood pressure lowering medications beginning 12 hours prior to obinutuzumab infusion and continuing until 1 hour after the end of the infusion. Consider therapy modification

Pentoxifylline: May enhance the hypotensive effect of Blood Pressure Lowering Agents. Monitor therapy

Phosphodiesterase 5 Inhibitors: May enhance the hypotensive effect of Blood Pressure Lowering Agents. Monitor therapy

Polymyxin B: May enhance the neuromuscular-blocking effect of Mecamylamine. Avoid combination

Prostacyclin Analogues: May enhance the hypotensive effect of Blood Pressure Lowering Agents. Monitor therapy

Quinagolide: May enhance the hypotensive effect of Blood Pressure Lowering Agents. Monitor therapy

Sulfonamides: May enhance the adverse/toxic effect of Mecamylamine. Avoid combination

Tetracycline Derivatives: May enhance the neuromuscular-blocking effect of Mecamylamine. Avoid combination

Urinary Acidifying Agents: May decrease the serum concentration of Mecamylamine. Monitor therapy

Yohimbine: May diminish the antihypertensive effect of Antihypertensive Agents. Monitor therapy

Adverse Reactions

Frequency not defined.

Cardiovascular: Orthostatic hypotension, syncope

Central nervous system: Altered mental status, choreiform movements, convulsions, fatigue, orthostatic dizziness, paresthesia, sedation

Endocrine & metabolic: Decreased libido

Gastrointestinal: Anorexia, constipation (sometimes preceded by small, frequent stools), glossitis, intestinal obstruction, nausea, vomiting, xerostomia

Genitourinary: Impotence, urinary retention

Neuromuscular & skeletal: Tremor, weakness

Ophthalmic: Blurred vision, mydriasis

Respiratory: Pulmonary fibrosis, pulmonary interstitial edema

Warnings/Precautions

Concerns related to adverse effects:

• CNS effects: CNS effects, including tremor, choreiform movements, mental aberrations, and convulsions may occur (rarely), especially with large doses or in patients with cerebral or renal insufficiency. In addition, dizziness, lightheadedness, or fainting may also occur.

• Paralytic ileus: Discontinue if signs of paralytic ileus occur (eg, frequent loose bowel movements with abdominal distention, decreased borborygmi)

Disease-related concerns:

• Cardiovascular disease: Use with caution in patients with marked cerebral and coronary arteriosclerosis or after a recent cerebral accident.

• Prostatic hyperplasia/urinary stricture: Use with caution in patients with prostatic hyperplasia, bladder obstruction, or urethral stricture; may cause urinary retention.

• Renal impairment: Use with caution in patients with renal impairment. When renal impairment is manifested by a rising or elevated BUN, use with extreme caution, if at all. Since mecamylamine is excreted unchanged in the urine, renal impairment may reduce elimination and increase the risk of adverse effects including hypotension; the risk for neurological adverse effects is increased especially when large doses are administered to patients with renal impairment.

Other warnings/precautions:

• Abrupt discontinuation: Do not abruptly discontinue.

Monitoring Parameters

Monitor blood pressure (assess in the erect position before initiation and with dose increases), orthostatic vital signs, and heart rate

Pregnancy Risk Factor

C

Pregnancy Considerations

Animal reproduction studies have not been conducted. Mecamylamine crosses the placenta.

Patient Education

• Discuss specific use of drug and side effects with patient as it relates to treatment. (HCAHPS: During this hospital stay, were you given any medicine that you had not taken before? Before giving you any new medicine, how often did hospital staff tell you what the medicine was for? How often did hospital staff describe possible side effects in a way you could understand?)

• Patient may experience fatigue, dry mouth, lack of appetite, nausea, vomiting, or loss of strength and energy. Have patient report immediately to prescriber blurred vision, burning or numbness feeling, decreased libido, sexual dysfunction, severe dizziness, passing out, diarrhea, abdominal edema, mood changes, mouth irritation, tongue irritation, seizures, severe constipation, severe abdominal pain, shortness of breath, urinary retention, muscle rigidity, tremors, or abnormal movements (HCAHPS).

• Educate patient about signs of a significant reaction (eg, wheezing; chest tightness; fever; itching; bad cough; blue skin color; seizures; or swelling of face, lips, tongue, or throat). Note: This is not a comprehensive list of all side effects. Patient should consult prescriber for additional questions.

Intended Use and Disclaimer: Should not be printed and given to patients. This information is intended to serve as a concise initial reference for healthcare professionals to use when discussing medications with a patient. You must ultimately rely on your own discretion, experience, and judgment in diagnosing, treating, and advising patients.

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