(-)-Salbutamol

Salbutamol is a beta(2)-adrenergic agonist and thus it stimulates beta(2)-adrenergic receptors. Binding of albuterol to beta(2)-receptors in the lungs results in relaxation of bronchial smooth muscles. It is believed that salbutamol increases cAMP production by activating adenylate cyclase, and the actions of salbutamol are mediated by cAMP. Increased intracellular cyclic AMP increases the activity of cAMP-dependent protein kinase A, which inhibits the phosphorylation of myosin and lowers intracellular calcium concentrations. A lowered intracellular calcium concentration leads to a smooth muscle relaxation and bronchodilation. In addition to bronchodilation, salbutamol inhibits the release of bronchoconstricting agents from mast cells, inhibits microvascular leakage, and enhances mucociliary clearance.

β2 adrenergic receptors on airway smooth muscle are Gs coupled and their activation by levosalbutamol leads to activation of adenylate cyclase and to an increase in the intracellular concentration of 3',5'-cyclic adenosine monophosphate (cyclic AMP). Increased cyclic AMP activates protein kinase A which itself inhibits the phosphorylation of myosin produces lower intracellular ionic calcium concentrations, inducing muscle relaxation. Increased cyclic AMP concentrations are also associated with the inhibition of the release of mediators from mast cells in the airways, potentially contributing to its benefit in asthma attacks.

Pure (R)-salbutamol formulation known as levosalbutamol is metabolised up to 12 times faster than (S)-salbutamol by intestine.

Hydrolyzed by esterases in tissue and blood to the active compound colterol. The drug is also conjugatively metabolized to salbutamol 4'-O-sulfate. Route of Elimination: Approximately 72% of the inhaled dose is excreted in the urine within 24 hours, 28% as unchanged drug and 44% as metabolite. Half Life: 1.6 hours

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LEVALBUTEROL

Mechanisms of Action [MoA] - Adrenergic beta2-Agonists

Established Pharmacologic Class [EPC] - beta2-Adrenergic Agonist

Levalbuterol is a beta2-Adrenergic Agonist. The mechanism of action of levalbuterol is as an Adrenergic beta2-Agonist.

LEVALBUTEROL

Inhalation delivers the medication directly into the airways and lungs, thereby minimizing side effects because of reduced systemic absorption of the inhaled medications.

excreted into the urine.