Isoetharine (Isoetarine) mesylate is an orally active selective agonist of β-adrenergic receptors. Isoetharine mesylate is a catechol-like agent and catechol O-methyltransferase (COMT) mediates its methylation. Isoetharine mesylate can promote the production of cAMP which stimulates the relaxation of smooth muscle cells and can be used as an emphysema, bronchitis and bronchodilator.