Complex sentence: Leukotrienes are involved in asthmatic and allergic reactions and act to sustain inflammatory reactions; several leukotriene receptor antagonists (e.g., montelukast and zafirlukast) are used to treat asthma.
Split into simpler sentences: Leukotrienes are involved in asthmatic and allergic reactions and act to sustain inflammatory reactions. Several leukotriene receptor antagonists such as montelukast and zafirlukast are used to treat asthma.