Drug of choice for exo-erythrocystic stage of malaria is ?
**Core Concept**
The exo-erythrocystic stage of malaria refers to the pre-erythrocytic stage, where the parasite develops within the hepatocytes of the liver. This stage is critical in the life cycle of the malaria parasite, as it is the period when the parasite undergoes asexual reproduction and develops into a form that can infect red blood cells.
**Why the Correct Answer is Right**
The drug of choice for the exo-erythrocystic stage of malaria is primaquine. Primaquine acts by targeting the liver stage of the malaria parasite, specifically the hypnozoite form, which is responsible for relapse in P. vivax and P. ovale infections. Primaquine is a 8-aminoquinoline that is activated in the acidic environment of the lysosome within the hepatocyte, where it disrupts the parasite's mitochondrial function, ultimately leading to its death.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect as it does not specifically target the liver stage of the malaria parasite.
**Option B:** This option is incorrect as it is not effective against the hypnozoite form of the malaria parasite.
**Option C:** This option is incorrect as it is not the primary drug of choice for the exo-erythrocystic stage of malaria.
**Clinical Pearl / High-Yield Fact**
It's essential to note that primaquine is not used for the treatment of P. falciparum infections, as it does not have any activity against the blood stage of this parasite. However, it is used for the radical cure of P. vivax and P. ovale infections to prevent relapse.
**Correct Answer: C. Primaquine**