metaproterenol sulfate
Alupent

Available forms
Available by prescription only
Aerosol inhaler: 0.65 mg/metered spray
Nebulizer inhaler: 0.4%, 0.6%, 5% solution
Syrup: 10 mg/5 ml
Tablets: 10 mg, 20 mg

Indications and dosages
 Bronchial asthma and reversible bronchospasm. Oral form. Adults and children older than age 9 or who weigh more than 27 kg (60 lb): 20 mg P.O. t.i.d. or q.i.d.
Children ages 6 to 9 or who weigh less than 27 kg: 10 mg P.O. t.i.d. or q.i.d.
Children younger than age 6: 1.3 to 2.6 mg/kg P.O. daily in divided doses.
Inhaled form
Adults and children age 12 and older: Administered by metered aerosol, two or three inhalations q 3 to 4 hours with at least 2 minutes between inhalations; no more than 12 inhalations in 24 hours. Administered by hand-bulb nebulizer, 10 inhalations of an undiluted 5% solution, or administered by intermittent positive pressure breathing, 0.3 ml (range, 0.2 to 0.3 ml of a 5% solution diluted in about 2.5 ml of a normal saline solution or 2.5 ml of a commercially available 0.4% or 0.6% solution for nebulization).
Children ages 6 to 11: 0.1 ml (range 0.1 to 0.2 ml) of 5% solution diluted with normal saline solution to final volume of 3 ml. Administer by nebulizer.
 Note: To relieve acute bronchospasm, usually don’t need to repeat more than q 4 hours. If part of bronchospastic pulmonary disease treatment regimen, administer t.i.d. to q.i.d.

Pharmacodynamics
Bronchodilator action: Metaproterenol relaxes bronchial smooth muscle and peripheral vasculature by stimulating beta₂-adrenergic receptors, thus decreasing airway resistance by way of bronchodilation. It has lesser effect on beta₁ receptors and has little or no effect on alpha-adrenergic receptors. In high doses, it may cause CNS and cardiac stimulation, resulting in tachycardia, hypertension, or tremors.

Pharmacokinetics
Absorption: Well-absorbed from the GI tract.
Distribution: Widely distributed throughout the body.
Metabolism: Extensively metabolized on first pass through the liver.
Excretion: Excreted in urine, mainly as glucuronic acid conjugates.

Contraindications and precautions
Contraindicated in patients hypersensitive to drug or its components and in those with tachycardia, arrhythmias related to tachycardia, peripheral or mesenteric vascular thrombosis, profound hypoxia, or hypercapnia. Also contraindicated during anesthesia with cyclopropane or halogenated hydrocarbon general anesthetics.
  Use cautiously in patients with hypertension, hyperthyroidism, heart disease, diabetes, or cirrhosis and in those receiving cardiac glycosides and in patients with sensitivity to parabens.

Interactions
Drug-drug. Beta blockers, especially propranolol: Antagonizes bronchodilating effects of metaproterenol. Avoid use together.
Cardiac glycosides, general anesthetics (especially chloroform, cyclopropane, halothane, and trichloroethylene), levodopa, theophylline derivatives, thyroid hormones: May increase potential for cardiac effects, including severe ventricular tachycardia, arrhythmias, and coronary insufficiency. Use together cautiously.
Contrast dyes (diatrizoates, iothalamate, ioversol, ioxaglate): May increase potential for neurologic effects. Use together cautiously.
MAO inhibitors, tricyclic antidepressants: May potentiate CV actions of these drugs. Use together cautiously.
Sympathomimetics: May produce additive effects and toxicity. Use together cautiously.
Xanthines, other sympathomimetics, other CNS-stimulating drugs: Increases CNS stimulation. Monitor patient closely.

Adverse reactions
CNS: nervousness, weakness, drowsiness, tremor, vertigo, headache.
CV: tachycardia, hypertension, palpitations, cardiac arrest.
GI: vomiting, nausea, heartburn, dry mouth.
Respiratory: paradoxical bronchiolar constriction with excessive use, cough, dry and irritated throat.
Skin: rash, hypersensitivity reactions.

Effects on lab test results
None reported.

Overdose and treatment
Signs and symptoms of overdose include exaggeration of common adverse reactions, particularly nausea and vomiting, arrhythmias, angina, hypertension, and seizures.
 Treatment includes supportive and symptomatic measures. Monitor vital signs closely. Support CV status. Use cardioselective beta₁-adrenergic blockers (acebutolol, atenolol, metoprolol) to treat symptoms with extreme caution; they may induce severe bronchospasm or asthmatic attack.

Special considerations
• Excessive or prolonged use may lead to decreased effectiveness.
• Avoid simultaneous administration of adrenocorticoid inhalation aerosol. Allow at least 5 minutes to lapse between using the two aerosols.
• Aerosol treatments may be used with oral tablet dosing.
• Monitor patient for signs and symptoms of toxic effects, such as nausea and vomiting, tremors, and arrhythmias.
• Periodically monitor pulmonary function.
• Drug may reduce sensitivity of spirometry in diagnosis of asthma.
• Adverse reactions are dose-related and characteristic of sympathomimetics, and may persist a long time because of the long duration of action of metaproterenol.
• Store tablets and oral solution at 59° to 86° F (15° to 30° C) in tight, light-resistant containers. Store oral inhalation and nebulizer solution at 59° to 86° F (15° to 30° C).
Pediatric patients
• Oral inhalation of aerosol in children younger than age 12 isn’t recommended because safety and efficacy haven’t been established. Safety and efficacy of oral preparations in children younger than age 6 haven’t been established.
Geriatric patients
• Geriatric patients may be more sensitive to the therapeutic and adverse effects of drug.

Patient education
• Instruct patient to use only as directed and to take no more than 2 inhalations at one time with 2-minute intervals between. Remind patient to save applicator; refills may be available.
• Tell patient to take missed dose if remembered within 1 hour. After 1 hour, patient should skip dose and resume regular schedule. The patient shouldn’t double the dose.
• Tell patient to store drug away from heat and light, and safely out of reach of children.
• Tell patient to call immediately if condition worsens or no relief occurs.
• Warn patient to avoid simultaneous use of adrenocorticoid aerosol and to allow at least 5 minutes to elapse between using the two aerosols.
• Tell patient that he may experience an unpleasant taste after using oral inhaler. Advise patient to rinse mouth with water after each use.
• Instruct patient to shake container, exhale through nose as completely as possible, administer aerosol while inhaling deeply through mouth, and hold breath for 10 seconds before exhaling slowly. Patient should wait 1 to 2 minutes before repeating inhalations.
• Tell patient that drug may have shorter duration of action after prolonged use. Advise patient to report failure to respond to usual dose.
• Warn patient not to increase dose or frequency unless prescribed; serious adverse reactions are possible.

Reactions may be common, uncommon, life-threatening, or COMMON AND LIFE THREATENING.
◆ Canada only
◇ Unlabeled clinical use