This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Asthma, Subject name: Pharmacology
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: 
Select and explain. 
A. Antagonize Leukotriene D4 receptor, B. Inhibits 5 -lipoxygenase, C. Inhibit phosphodiesterases, D. Stimulate P2 receptors
B: Inhibits 5 -lipoxygenase
Answer: B: Inhibits 5 -lipoxygenase 
Explanation: 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.