This guide opens by presenting the most recent updates on the improvement of montelukast stability and bioavailability, along with some innovative formulations produced by this research. Montelukast is a leukotriene modifier with bronchoprotective and anti-inflammatory actions frequently used in asthma management. As such, the authors go on to assess the impact of the addition of montelukast to ongoing asthma treatment in terms of improvement in clinical parameters, symptom control and quality of life. The closing chapter focuses on leukotrienes, formed by leukocytes, which are inflammatory mediators that play an active role in early and late-phase immune response. This group includes montelukast, zafirlukast and prankulast.