## **Core Concept**
The question tests knowledge of antimalarial drugs and their side effect profiles, specifically focusing on neuropsychiatric adverse reactions. Antimalarial drugs are crucial in the management and prophylaxis of malaria, but they can have various side effects. Neuropsychiatric adverse reactions include symptoms like hallucinations, psychosis, and depression.

## **Why the Correct Answer is Right**
Mefloquine is well-documented to cause neuropsychiatric adverse reactions. It is a quinine derivative used for malaria prophylaxis and treatment. The mechanism behind its neuropsychiatric side effects is not entirely clear, but it is thought to relate to its effect on the central nervous system. Mefloquine can cause a range of neuropsychiatric symptoms, including anxiety, depression, hallucinations, and even psychosis in some cases.

## **Why Each Wrong Option is Incorrect**
- **Option A:** Chloroquine is an antimalarial drug that can have side effects like retinal toxicity and cardiac issues but is less commonly associated with neuropsychiatric adverse reactions compared to mefloquine.
- **Option B:** Artesunate is a derivative of artemisinin used in the treatment of malaria. While it has a generally favorable side effect profile, it is not particularly known for causing neuropsychiatric adverse reactions.
- **Option D:** Primaquine is used for the radical cure of P. vivax and P. ovale malaria. Its side effects include hemolysis, especially in individuals with G6PD deficiency, but it is not notably associated with neuropsychiatric reactions.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that mefloquine is associated with a higher risk of neuropsychiatric side effects, such as anxiety and hallucinations. Due to these potential side effects, mefloquine is sometimes reserved for travelers who have no other options for malaria prophylaxis, and its use is often accompanied by careful monitoring for adverse effects.

## **Correct Answer:** C. Mefloquine