Active ingredient: Metaproterenol - Brands, Medical Use, Clinical Data

Brands, Medical Use, Clinical Data

Drug Category

• Tocolytic Agents
• Bronchodilator Agents

Dosage Forms

• Inhalation

Brands / Synonyms

Alotec; Alupent; Metaprel; Metaproterenol; Metaproterenol Polistirex; Metaproterenol Polistirex [Usan]; Metaproterenol Sulfate; Novasmasol; Orciprenalina [Inn-Spanish]; Orciprenaline; Orciprenalinum [Inn-Latin]; Prometa

Indications

For the treatment of bronchospasm, chronic bronchitis, asthma, and emphysema.

Pharmacology

Metaproterenol, a synthetic amine, is structurally and pharmacologically similar to isoproterenol. Metaproterenol is used exclusively as a bronchodilator. The pharmacologic effects of beta adrenergic agonist drugs, such as Metaproterenol, are at least in part attributable to stimulation through beta adrenergic receptors of intracellular adenyl cyclase, the enzyme which catalyzes the conversion of adenosine triphosphate (ATP) to cyclic- 3',5'- adenosine monophosphate (c-AMP). Increased c-AMP levels are associated with relaxation of bronchial smooth muscle and inhibition of release of mediators of immediate hypersensitivity from cells, especially from mast cells.

Mechanism of Action

Metaproterenol is a moderately selective beta(2)-adrenergic agonist that stimulates receptors of the smooth muscle in the lungs, uterus, and vasculature supplying skeletal muscle, with minimal or no effect on alpha-adrenergic receptors. Intracellularly, the actions of metaproterenol are mediated by cAMP, the production of which is augmented by beta stimulation. The drug is believed to work by activating adenylate cyclase, the enzyme responsible for producing the cellular mediator cAMP.

Absorption

3% (oral bioavailability of 40%)

Toxicity

Symptoms of overdose include angina, hypertension or hypotension, arrhythmias, nervousness, headache, tremor, dry mouth, palpitation, nausea, dizziness, fatigue, malaise and insomnia. LD₅₀=42 mg/kg (orally in rat).

Biotrnasformation / Drug Metabolism

Hepatic and gastric. The major metabolite, metaproterenol-3-0-sulfate, is produced in the gastrointestinal tract. Alupent is not metabolized by catechol-0-methyltransferase nor have glucuronide conjugates been isolated to date.

Contraindications

CONTRAINDICATIONS

Use in patients with cardiac arrhythmias associated with tachycardia is
contraindicated.

Although rare, immediate hypersensitivity reactions can occur. Therefore,
Alupent® (metaproterenol sulfate USP) Inhalation Aerosol is contraindicated
in patients with a history of hypersensitivity to any of its components.

Drug Interactions

Other beta adrenergic aerosol bronchodilators should not be used concomitantly with Alupent^® (metaproterenol sulfate USP) because they may have additive effects. Beta adrenergic agonists should be administered with caution to patients being treated with monoamine oxidase inhibitors or tricyclic antidepressants, since the action of beta adrenergic agonists on the vascular system may be potentiated.