**Core Concept**
Amyl nitrite is a vasodilator used to counteract the effects of cyanide poisoning, which occurs due to its inhibition of cellular respiration and the mitochondrial enzyme cytochrome c oxidase. This leads to a decrease in ATP production and ultimately cellular asphyxiation.

**Why the Correct Answer is Right**
The mechanism of action of amyl nitrite in cyanide poisoning involves the formation of methemoglobin, which has a higher affinity for cyanide than cytochrome c oxidase. This results in the binding of cyanide to methemoglobin, thereby reducing its availability to inhibit cytochrome c oxidase and allowing cellular respiration to occur. Amyl nitrite also increases oxygen delivery to tissues by causing vasodilation, further aiding in the recovery from cyanide poisoning.

**Why Each Wrong Option is Incorrect**
* **Option A:** Digitalis poisoning is treated with digoxin-specific antibodies, not amyl nitrite. Digitalis inhibits the Na+/K+ ATPase pump, leading to an increase in intracellular calcium and cardiac arrhythmias.
* **Option B:** Organophosphate poisoning is treated with atropine and pralidoxime, which counteract the effects of acetylcholinesterase inhibition. Amyl nitrite is not effective in this scenario.
* **Option C:** Barbiturate poisoning is treated with supportive care and activated charcoal, but not amyl nitrite. Barbiturates are central nervous system depressants that can cause respiratory depression and coma.

**Clinical Pearl / High-Yield Fact**
Amyl nitrite is one of the earliest vasodilators used in medicine, and its use as an antidote for cyanide poisoning dates back to the early 20th century. It is often used in combination with other antidotes, such as sodium thiosulfate, to treat cyanide poisoning.

**Correct Answer: C. Barbiturate poisoning is treated with supportive care and activated charcoal, but not amyl nitrite. Barbiturates are central nervous system depressants that can cause respiratory depression and coma.