<prompt> A 34 year old man with a long history of asthma is referred to pulmonologist. The physician decides to prescribe zileuton. The mechanism of action of this drug is to:Antagonize Leukotriene D4 receptorInhibits 5 -lipoxygenaseInhibit phosphodiesterasesStimulate P2 receptors  <response>: Ans. b Inhibits 5 -lipoxygenase Leukotrienes are biochemical mediators that contribute to asthma symptoms Contracting airway smooth muscle Increasing vascular permeability and mucus secretion Attracting and activating airway inflammatory cells Zileuton is a 5-lipoxygenase inhibitor that decreases leukotriene production, and zafirlukast and montelukast are cysteinyl leukotriene receptor antagonists. They are useful to prevent asthma attacks and cause modest improvements in lung function. They lessen the need for b2 - agonist rescue therapy. 