**Core Concept**
Ketorolac is a nonsteroidal anti-inflammatory drug (NSAID) that acts as a potent inhibitor of cyclooxygenase (COX) enzymes, specifically COX-1 and COX-2. This action leads to a reduction in prostaglandin synthesis, which in turn results in decreased inflammation and pain.

**Why the Correct Answer is Right**
Ketorolac is a selective COX-1 inhibitor, which means it preferentially blocks the COX-1 enzyme over COX-2. This is in contrast to many other NSAIDs, which are non-selective and block both enzymes. The selective inhibition of COX-1 is thought to be responsible for ketorolac's lower gastrointestinal toxicity compared to non-selective NSAIDs. Additionally, ketorolac has a high affinity for COX-1, which allows it to effectively reduce prostaglandin synthesis and subsequent pain and inflammation.

**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect, as ketorolac is not an opioid analgesic.
**Option B:** Incorrect, as ketorolac's mechanism of action is through inhibition of COX enzymes, not through modulation of the opioid receptor.
**Option C:** Incorrect, as ketorolac is not a selective COX-2 inhibitor; in fact, it is more selective for COX-1.

**Clinical Pearl / High-Yield Fact**
Ketorolac is often used as a short-term alternative to opioids for acute pain management, particularly in the postoperative setting. Its mechanism of action and selective COX-1 inhibition make it a useful option for patients who require potent analgesia with a lower risk of gastrointestinal side effects.

**Correct Answer:** C.