**Question:** Prolonged administration of Sodium nitroprusside can cause poisoning of:

**Core Concept:** Sodium nitroprusside is a medication used as a vasodilator in the treatment of hypertension, and it works by activating soluble guanylate cyclase in the smooth muscle cells of blood vessels, leading to vasodilation and a reduction in blood pressure. However, prolonged usage can lead to cyanide poisoning due to the formation of cyanide from nitroprusside.

**Why the Correct Answer is Right:** Cyanide is a highly toxic and poisonous substance. When administered over a prolonged period, nitroprusside is converted into cyanide. Cyanide interferes with cellular respiration by inhibiting the enzyme cytochrome c oxidase, thus leading to cell damage and potential organ failure.

**Why Each Wrong Option is Incorrect:**

A. **Sodium bicarbonate (Option A):** This is incorrect because sodium bicarbonate acts as a buffer against excess hydrogen ions in the body and does not directly counteract the toxic effects of cyanide.

B. **Hydrogen cyanide (Option B):** Although hydrogen cyanide is a component of cyanide, it is not the actual poison causing the toxic effects, but rather a precursor to cyanide formation from nitroprusside.

C. **Oxides of nitrogen (Option C):** This is incorrect because oxides of nitrogen are unrelated to the toxic effects of cyanide and are unrelated to nitroprusside administration.

D. **Acetaminophen (Option D):** Acetaminophen is an analgesic and antipyretic, unrelated to cyanide poisoning and nitroprusside administration.

**Clinical Pearl:** Cyanide poisoning is a serious complication of prolonged nitroprusside administration, and monitoring of serum nitroprusside levels and promptly discontinuing nitroprusside when therapeutic goals are achieved can help prevent this complication. In case of cyanide poisoning, administration of sodium thiosulfate is the standard treatment.

**Correct Answer:** Cyanide (Option E)

**Why Cyanide is the Correct Answer:** As mentioned earlier, cyanide is a toxic substance formed from the breakdown of nitroprusside, a medication used to treat hypertension. Cyanide interferes with cellular respiration by inhibiting the enzyme cytochrome c oxidase, leading to organ dysfunction and potential death if not treated promptly. In clinical practice, monitoring nitroprusside levels and promptly discontinuing its administration when therapeutic goals are achieved helps prevent cyanide poisoning. In case cyanide poisoning occurs, sodium thiosulfate is the standard treatment.