Metaproterenol Sulfate Inhalation Solution is indicated as a bronchodilator for bronchial asthma and for reversible bronchospasm which may occur in association with bronchitis and emphysema.Following controlled single dose studies by an intermittent positive pressure breathing apparatus (IPPB) and by hand bulb nebulizers, significant improvement (15% or greater increase in FEV1) occurred within 5 to 30 minutes and persisted for periods varying from 2 to 6 hours.In these studies, the longer duration of effect occurred in the studies in which the drug was administered by IPPB, i.e.
6 hours versus 2 to 3 hours when administered by hand bulb nebulizer.
In these studies the doses used were 0.3 mL by IPPB and 10 inhalations by hand bulb nebulizer.In controlled repetitive dosing studies by IPPB and by hand bulb nebulizer the onset of effect occurred within 5 to 30 minutes and duration ranged from 4 to 6 hours.
In these studies the doses used were 0.3 mL b.i.d.
when given by IPPB and 10 inhalations q.i.d.
(no more often than q 4h) when given by hand bulb nebulizer.
As in the single dose studies, effectiveness was measured as a sustained increase in FEV1 of 15% or greater.
In these repetitive dosing studies there was no apparent difference in duration between the two methods of delivery.During other clinical tolerance studies, metaproterenol was administered q.i.d.
(by nebulizer) for periods of 60 and 90 days.
On specified days before, during and after these open label trials, patients were referred to a laboratory where the effects of single doses of metaproterenol and isoproterenol on pulmonary function were recorded (in a double blind crossover controlled setting).Both drugs continued to exert significant improvement in function throughout this period of treatment.
Use in patients with cardiac arrhythmias associated with tachycardia is contraindicated.Although rare, immediate hypersensitivity reactions can occur.Therefore, Metaproterenol Sulfate Inhalation Solution is contraindicated in patients with a history of hypersensitivity to any of its components.
Excessive use of adrenergic aerosols is potentially dangerous.
Fatalities have been reported following excessive use of metaproterenol sulfate as with other sympathomimetic inhalation preparations, and the exact cause is unknown.Cardiac arrest was noted in several cases.Paradoxical bronchoconstriction with repeated excessive administration has been reported with sympathomimetic agents.Patients should be advised to contact their physician in the event that they do not respond to their usual dose of sympathomimetic amine aerosol.