**Core Concept:** Cyanide poisoning is a life-threatening emergency caused by the inhibition of mitochondrial complex IV in the electron transport chain, leading to decreased oxygen utilisation and cellular hypoxia. Cyanide competitively inhibits cytochrome c oxidase, the terminal enzyme in the electron transport chain, and thereby reduces cellular oxygen utilization.

**Why the Correct Answer is Right:**

The correct answer is the use of sodium thiosulfate. Sodium thiosulfate acts as a cyanide scavenger, binding to and neutralizing cyanide ions, allowing the body to excrete the toxic substance through urine. This process enhances cellular oxygen utilization and reduces the severity of cyanide poisoning.

**Why Each Wrong Option is Incorrect:**

A. Hydrogen sulfide (H2S) is a toxic gas, but it is not the primary treatment for cyanide poisoning. Instead, sodium thiosulfate is the appropriate agent for cyanide detoxification.

B. Hydroxocobalamin (Cyanokit) is used for cyanide detoxification, but it is not the primary treatment option for cyanide poisoning. Sodium thiosulfate is the correct choice.

C. Naloxone, an opioid antagonist, is used for opioid overdose reversal but is not effective in treating cyanide poisoning. Sodium thiosulfate is the appropriate agent for cyanide detoxification.

D. Oxygen therapy is a supportive measure for cyanide poisoning patients, but it is not the primary treatment. Sodium thiosulfate is the appropriate agent for cyanide detoxification.

**Clinical Pearl:** In cases of cyanide poisoning, it is essential to promptly administer sodium thiosulfate (50-100g IV over 10-15 minutes) to neutralize cyanide ions and enhance cellular oxygen utilization. Timing is crucial in treating cyanide poisoning, as early intervention can improve patient outcomes.

**Correct Answer:**

The correct answer is B. Hydroxocobalamin (Cyanokit) is an alternative agent used for cyanide detoxification. It forms a complex with cyanide, preventing its interaction with cellular components and enabling its excretion through urine.

**Why Each Wrong Option is Incorrect:**

A. Sodium thiosulfate is the primary treatment for cyanide poisoning due to its ability to directly bind with cyanide ions and neutralize them, thereby improving cellular oxygen utilization and enhancing oxygen delivery to vital organs.

C. Naloxone is used for opioid overdose reversal, not cyanide poisoning. It acts as an antagonist to opioids, binding with opioid receptors and preventing their effects.

D. Oxygen therapy is supportive care for cyanide poisoning patients by increasing oxygen delivery to tissues. However, it is not the primary treatment for cyanide poisoning.

In summary, hydroxocobalamin (Cyanokit) is a secondary treatment option for cyanide poisoning, while sodium thiosulfate is