DUAKLIR PRESSAIR

DUAKLIR PRESSAIR contains two bronchodilators: aclidinium a long-acting muscarinic antagonist (also known as an anticholinergic) and formoterol a long-acting beta2-adrenergic agonist. Further information regarding these two substances is provided below. The mechanism of action described below for the individual components apply to DUAKLIR PRESSAIR. These drugs represent two different classes of medications (a long-acting antimuscarinic agent and a selective long-acting beta2-adrenergic receptor agonist) that have different effects on clinical and physiological indices of COPD.

Aclidinium bromide

Aclidinium bromide is a long-acting antimuscarinic agent, which is often referred to as an anticholinergic. It has similar affinity to the subtypes of muscarinic receptors M1 to M5. In the airways, it exhibits pharmacological effects through inhibition of M3 receptors at the smooth muscle leading to bronchodilation. The competitive and reversible nature of antagonism was shown with human and animal origin receptors and isolated organ preparations. In preclinical in vitro as well as in vivo studies, prevention of acetylcholine-induced bronchoconstriction effects was dose-dependent and lasted longer than 24 hours. The clinical relevance of these findings is unknown. The bronchodilation following inhalation of aclidinium bromide is predominantly a site-specific effect.

Formoterol fumarate

Formoterol fumarate is a long-acting selective beta2-adrenergic receptor agonist (LABA) (beta2-agonist). Inhaled formoterol fumarate acts locally in the lung as a bronchodilator. In-vitro studies have shown that formoterol has more than 200-fold greater agonist activity at beta2-receptors than at beta1-receptors. The in-vitro binding selectivity to beta2-over beta1-adrenoceptors is higher for formoterol than for albuterol (5 times), whereas salmeterol has a higher (3 times) beta‑selectivity ratio than formoterol.

Although beta2-receptors are the predominant adrenergic receptors in bronchial smooth muscle and beta1-receptors are the predominant receptors in the heart, there are also beta2-receptors in the human heart comprising 10% to 50% of the total beta-adrenergic receptors. The precise function of these receptors has not been established, but they raise the possibility that even highly selective beta2-agonists may have cardiac effects.

The pharmacologic effects of beta2-adrenoceptor agonist drugs, including formoterol, are at least in part attributable to stimulation of intracellular adenyl cyclase, the enzyme that catalyzes the conversion of adenosine triphosphate (ATP) to cyclic-3', 5'-adenosine monophosphate (cyclic AMP). Increased cyclic AMP levels cause relaxation of bronchial smooth muscle and inhibition of release of mediators of immediate hypersensitivity from cells, especially from mast cells.

In vitro tests show that formoterol is an inhibitor of the release of mast cell mediators, such as histamine and leukotrienes, from the human lung. Formoterol also inhibits histamine-induced plasma albumin extravasation in anesthetized guinea pigs and inhibits allergen-induced eosinophil influx in dogs with airway hyper responsiveness. The relevance of these in vitro and animal findings to humans is unknown.