Metaproterenol

Mechanism :

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 orciprenaline 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.

Indication :

Asthma
Bronchospasm
Chronic Bronchitis
Emphysema

Contraindications :

Hypersensitivity, Tachyarrhythmias; Caution if MAO inhibitor or TCA use w/in 14 days.

Caution if ischemic heart disease, HTN, arrhythmias, hypokalemia, diabetes mellitus, seizure disorder, hyperthyroidism, unusually responsive to sympathomimetic amines.

Dosing :

Nebuliser:

Infants and children: 0.5 to 1 mg/kg (0.01 to 0.02 mL/kg of 5% solution); minimum dose: 5 mg (0.1 mL); maximum dose: 15 mg (0.3 mL); every 4 to 6 hours.

Oral:

<2 years: 0.4 mg/kg/dose in 3 to 4 divided doses a day.

2 to 6 years: 1.3 to 2.6 mg/kg/day divided every 6 to 8 hours.

6 to 9 years: 10 mg 3 to 4 times a day.

>9 years: 20 mg 3 to 4 times a day.

Inhalation Aerosol:

>12 years: 2 to 3 inhalations every 3 to 4 hours, up to 12 inhalations in 24 hours.

Adverse Effect :

More common: Tachycardia, tremors, nervousness.

Rare: Blurred vision, dizziness, fainting, headache, fever, chills, cough, joint pains, increased sweating, diarrhoea, loss of appetite, nausea, heartburn, pharyngitis, insomnia, chest pain.

Interaction :

Acebutolol: Antagonism.
Alseroxylon: Increased arterial pressure.
Amitriptyline: The tricyclic antidepressant, amitriptyline, increases the sympathomimetic effect of orciprenaline.
Amoxapine: The tricyclic antidepressant, amoxapine, increases the sympathomimetic effect of orciprenaline.
Atenolol: Antagonism.
Betaxolol: Beta-Blockers (Beta1 Selective) like betaxolol may diminish the bronchodilator effect of Beta2-Agonists like orciprenaline. Therapy should be monitored.
Bevantolol: Antagonism.
Bisoprolol: Antagonism.
Carteolol: Antagonism.
Carvedilol: Antagonism.
Clomipramine: The tricyclic antidepressant, clomipramine, increases the sympathomimetic effect of orciprenaline.
Deserpidine: Increased arterial pressure.
Desipramine: The tricyclic antidepressant, desipramine, increases the sympathomimetic effect of orciprenaline.
Doxepin: The tricyclic antidepressant, doxepin, increases the sympathomimetic effect of orciprenaline.
Esmolol: Antagonism.
Imipramine: The tricyclic antidepressant, imipramine, increases the sympathomimetic effect of orciprenaline.
Isocarboxazid: Increased arterial pressure.
Labetalol: Antagonism.
Linezolid: Possible increase of arterial pressure.
Methyldopa: Increased arterial pressure.
Metoprolol: Antagonism.
Midodrine: Increased arterial pressure.
Moclobemide: Moclobemide increases the sympathomimetic effect of orciprenaline.
Nadolol: Antagonism.
Nortriptyline: The tricyclic antidepressant, nortriptyline, increases the sympathomimetic effect of orciprenaline.
Oxprenolol: Antagonism.
Pargyline: Increased arterial pressure.
Penbutolol: Antagonism.
Phenelzine: Increased arterial pressure.
Pindolol: Antagonism.
Practolol: Antagonism.
Propranolol: Antagonism.
Protriptyline: The tricyclic antidepressant, protriptyline, increases the sympathomimetic effect of orciprenaline.
Rasagiline: Increased arterial pressure.
Reserpine: Increased arterial pressure.
Sotalol: Antagonism.
Timolol: Antagonism.
Tranylcypromine: Increased arterial pressure.
Trimipramine: The tricyclic antidepressant, trimipramine, increases the sympathomimetic effect of orciprenaline.

Hepatic Dose :

No dosage adjustments are recommended.