(-)-Salbutamol

DescriptionSalbutamol is a bronchodilator medication that eases muscle tension in the airways adjoining with the lungs and enhances the flow of air circulating through the lungs. It is a short-acting medication that is used in the treatment of acute bronchopulmonary disorders which may include chronic obstructive pulmonary disorders (COPD), and chronic instances of bronchospasm resultant of acute bronchitis and bronchial asthma. It can also be used for the prophylactic treatment of training-induced bronchospasm. Salbutamol indicates 29 times more selectivity for beta2 receptors as compared to beta1 receptors, which gives it a higher specificity for adrenergic receptors positioned in the heart. Salbutamol comprises a racemic combination of Sand Risomers, where the R-isomer illustrates a higher affinity (about 150 times more) than the S-isomer, which is directly linked to increased toxicity. This has also influenced the development of levalbuterol.

DescriptionLevalbuterol was launched in the US for the treatment or prevention of bronchospasm in patients with reversible obstructive airway disease. It is the single R-enantiomer version of racemic albuterol (salbutamol) marketed for more than 30 years as a mainstay in the treatment of asthma. The R-isomer can be obtained with an excellent optical purity by enantiomeric purification based on the separation of diastereomeric tartrates. This isomer retains solely the desired bronchodilating effect of the racemic mixture due to a potent agonistic effect on β2-adrenoceptors, with a lower incidence of β- mediated side effects such as pulse rate increase, tremor and decrease in blood glucose and potassium levels. A pivotal clinical trial with two doses of levalbuterol and racemic albuterol, given by nebulization, demonstrated a greater improvement in lung function for the pure enantiomer levalbuterol.

Uses(R)-Salbutamol is used in composition and methods to reduce beta-agonist-mediated tachyphylaxis.

UsesSalbutamol is the β2-agonist used most commonly for the prevention and treatment of bronchospasm. I t is most commonly administered in its inhaled form by metered-dose inhaler (1–2 puffs of 100μg each) or via nebuliser in more severe cases of bronchospasm (2.5–5mg). In patients with lifethreatening asthma it may be administered i.v. as both a bolus (250μg) and infusion (3–20μgmin –1). Intravenous administration requires cardiac monitoring as tachyarrhythmias may be significant. Salbutamol may also be used in the management of hyperkalaemia, temporarily driving K+ intracellularly via stimulation of the Na+–K+ ATPase pump.