Salmol Expectorant Mechanism of Action

Pharmacology: Pharmacodynamics: Salbutamol is sympathomimetic agent that stimulate beta₂- adrenergic receptors. Salbutamol relaxes the bronchial smooth muscle with little effect on heart rate.
Guaifenesin is an expectorant which increases respiratory tract fluid secretions and helps to loosen phlegm and brochial secretions. By reducing the viscosity of secretions and increasing sputum volume, guaifenesin increases the efficiency of the cough reflex and of ciliary action in removing accumulated secretions from the trachea and bronchi.
Pharmacokinetics: Salbutamol sulfate is rapidly and well-absorbed following oral administration. Peak plasma concentrations occur within about 2 hours following administration of oral solution. Salbutamol crosses the blood-brain barrier, reaching the brain at concentrations that are approximately 5% of plasma concentrations. Salbutamol apparently crosses the placenta, but it is not known whether salbutamol is distributed into milk. After oral administration, the half-life of salbutamol is 5 - 6 hours. Salbutamol is extensively metabolized in the liver, mainly to salbutamol 4'-O-sulfate which has little effect or no β-adrenergic blocking effect. Salbutamol and its metabolites are rapidly excreted in urine and feces. About 75% of single dose oral administration is excreted in urine within 72 hours, mainly as the major metabolite; about 4% of the dose is excreted in feces.
Guaifenesin is readily absorbed from the gastrointestinal tract and rapidly metabolized and excreted in the urine. Guaifenesin has a plasma half-life of 1 hour. The major urinary metabolite is β-(2-methoxyphenoxy) lactic acid.