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Pharmacodynamics and Pharmacokinetics: Salbutamol is a direct acting sympathomimetic agent that acts selectively on beta-2 adrenergic receptors in the bronchial muscles. This results in bronchodilation thereby relieving bronchospasm. It has little or no action on cardiac receptors (beta-1 adrenergic receptors in the heart) so it produces much less cardiac stimulation. Salbutamol therefore relaxes bronchial smooth muscles and expands or dilates the air passages to improve airflow.
Salbutamol also enhances mucociliary functions to help promote efficient mucus expectoration.
Guaifenesin promotes efficient expectoration of abnormal mucus secretions that accompany certain respiratory tract disorders. It is reported to increase the volume and reduces the viscosity of tenacious sputum.
Guaifenesin effectively loosens and dissolves excessive, viscid or thick mucus secretions present in the respiratory tract, thereby facilitating expectoration of bronchial mucus secretions that obstruct the respiratory air passages.
Following oral administration, salbutamol is well-absorbed from the gastrointestinal tract then metabolized in the liver. In the majority of patients, the effects of oral salbutamol usually lasts for 4-6 hours.
Salbutamol is excreted in the urine within 48-72 hours after oral administration, little is excreted via the feces.
Guaifenesin is well-absorbed from the gastrointestinal tract following oral administration. After metabolism, guaifenesin is excreted in the urine.
