**Core Concept**
Pure opiate antagonists are a class of medications that competitively block μ-opioid receptors without agonistic effects. This class of drugs is used to counteract opioid overdose and reverse opioid-induced respiratory depression.

**Why the Correct Answer is Right**
Naloxone is a pure opiate antagonist that rapidly reverses opioid-induced respiratory depression by competitively binding to μ-opioid receptors, thereby blocking the action of endogenous opioids and exogenously administered opioids. This action is due to its high affinity for μ-opioid receptors and its ability to cross the blood-brain barrier. Naloxone's mechanism of action is independent of the opioid receptor subtype, making it a universal antagonist for opioid receptors.

**Why Each Wrong Option is Incorrect**
**Option A:** Naltrindole is a selective κ-opioid receptor antagonist, not a pure opiate antagonist, as it specifically targets κ-opioid receptors without affecting μ-opioid receptors.
**Option B:** Nalorphine is a mixed opioid agonist-antagonist, as it exhibits partial agonist activity at μ-opioid receptors and antagonist activity at κ-opioid receptors.
**Option C:** Pentazocine is also a mixed opioid agonist-antagonist, with agonist activity at κ-opioid receptors and antagonist activity at μ-opioid receptors.

**Clinical Pearl / High-Yield Fact**
Naloxone's rapid onset of action and short duration of action make it an ideal choice for emergency reversal of opioid-induced respiratory depression. However, its short half-life requires repeated dosing to maintain efficacy.

**Correct Answer: D. Naloxone**