Asmalin Mechanism of Action

Pharmacology: Pharmacodynamics: Salbutamol is a selective short-acting beta₂-adrenergic agonist with preferential effect on beta₂-adrenergic receptors found in the respiratory tract. It stimulates adenyl cyclase, the enzyme which catalyzes the conversion of adenosine triphosphate (ATP) to cyclic-3',5'-adenosine monophosphate (cAMP). cAMP mediates cellular responses such as bronchial smooth muscle relaxation resulting in bronchodilation.
Pharmacokinetics: Syrup: Salbutamol is readily absorbed from the gastrointestinal tract after oral administration. Salbutamol's onset of action is within 30 minutes, peaks in 2-3 hours after the dose, and persists for 6 hours. The plasma half-life of salbutamol is from 4-6 hours. It is extensively metabolized in the liver, being converted to salbutamol 4'O-sulfate. Salbutamol and its metabolites are rapidly excreted in urine and feces. After an oral administration of salbutamol to healthy individuals, about 75% of a single dose is excreted in urine within 72 hours, mainly as the major metabolite; about 4% of the dose is excreted in feces.
Pulmoneb: Onset of bronchodilation is within 5 minutes after nebulization with Salbutamol, peaks in 1 to 2 hours, and persists for 3 to 4 hours. Bronchodilation generally persist up to 6 hours or longer. After inhalation of nebulized salbutamol, less than 20% of the drug is absorbed in the lungs. The remaining amount is retained in the nebulizer and recovered in expired air. Much of the salbutamol dose delivered by oral inhalation is deposited on the buccal mucosa and subsequently swallowed and absorbed from the gastrointestinal tract.
Salbutamol is metabolized in the liver, being converted to salbutamol 4'-O-sulfate. This is then excreted in the urine and feces. In patients with asthma, about 70% of the inhaled dose is excreted in urine as unchanged drug and metabolites within 24 hours, and 80 to 100% within 72 hours. About 30% of the inhaled dose is excreted unchanged in the urine in 24 hours. About 10% of the inhaled dose may be excreted in the feces.
Animal studies show that salbutamol can cross the blood-brain barrier and the placenta. It may be secreted in breast milk but the concentrations are not known.