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
Zileuton is - 
Select and explain. 
A. 5 lipooxygenase inhibitor, B. TX A2 inhibitor, C. Leukotriene receptor antagonist, D. Prostaglandins synthesis inhibitor
A: 5 lipooxygenase inhibitor
Answer: A: 5 lipooxygenase inhibitor 
Explanation: Ans. is 'a' i.e., 5 lipooxygenase inhibitor 5-lipoxygenase inhibitoro 5-lipoxygenase involved in production of leukotrienes especially LTB4 (chemoattractant) and LTC4, LTD4 (Bronchoconstrictor). These are the most important mediators in bronchial asthma.o Zileuton inhibits 5-lip>>xygenase and thereby the production of leukotrienes. Therefore, Zileuton is useful in the treatment of asthma.