**Question:** End point of D/C is -

A. Inhibition of COX enzymes
B. Inhibition of lipoxygenase enzymes
C. Activation of prostaglandin synthesis
D. Inhibition of nitric oxide synthesis

**Correct Answer:** B. Inhibition of lipoxygenase enzymes

**Core Concept:**
The correct answer is based on understanding the role of cyclooxygenase (COX) and lipoxygenase (LOX) enzymes in the biosynthesis of eicosanoids, which are lipid mediators involved in various physiological processes, including inflammation, pain, and fever. Inhibition of COX enzymes leads to the production of prostaglandins, which are involved in pain and inflammation. Inhibition of LOX enzymes, on the other hand, results in the production of leukotrienes and hydroxyeicosatetraenoic acids, which contribute to inflammation, bronchoconstriction, and platelet aggregation.

**Why the Correct Answer is Right:**
The correct answer, inhibition of lipoxygenase enzymes (Option B), is right because it is the primary mechanism of action for nonsteroidal anti-inflammatory drugs (NSAIDs). NSAIDs target both COX and LOX enzymes, but since the question focuses on the end point, we only consider the effect on LOX enzymes. NSAIDs, such as ibuprofen and naproxen, primarily inhibit the COX enzymes, leading to a reduction in prostaglandin synthesis and subsequent analgesic, anti-inflammatory, and antipyretic effects.

**Why Each Wrong Option is Incorrect:**
A. Inhibition of COX enzymes (Option A) is incorrect because it does not result in the production of leukotrienes and hydroxyeicosatetraenoic acids, which are involved in inflammation, bronchoconstriction, and platelet aggregation. Inhibition of COX enzymes leads to a reduction in prostaglandin synthesis, resulting in analgesic, anti-inflammatory, and antipyretic effects.

C. Activation of prostaglandin synthesis (Option C) is incorrect because it contradicts the overall goal of NSAIDs, which is to reduce inflammation, pain, and fever. Activation of prostaglandin synthesis would exacerbate these symptoms rather than alleviate them.

D. Inhibition of nitric oxide synthase (Option D) is incorrect because nitric oxide (NO) plays a crucial role in various physiological processes, such as vasodilation, neurotransmission, and mucosal protection in the gastrointestinal tract. Inhibition of NO synthesis would negatively affect these processes and potentially lead to gastrointestinal complications like ulcers and bleeding.

**Clinical Pearl:**
Understanding the distinction between COX and LOX enzymes is crucial for understanding the mechanism of action of NSAIDs. The primary goal of NSAIDs is to reduce inflammation, pain, and fever, which is achieved by inhibiting COX enzymes. Inhibition of LOX enzymes is a secondary effect that results from the primary action on COX enzymes and does not contribute to the overall therapeutic effect.