**Question:** Tissue schizontocide which prevents relapse of vivax malaria -

A. Chloroquine
B. Artemisinin
C. Primaquine
D. Mefloquine

**Core Concept:**
Malaria is a parasitic disease caused by the Plasmodium species, specifically Plasmodium falciparum, Plasmodium vivax, Plasmodium ovale, Plasmodium malariae, and Plasmodium knowlesi. Vivax malaria is caused by Plasmodium vivax and Plasmodium ovale, which can undergo hepatic hypnozoite stage to cause relapses months after the initial infection.

**Why the Correct Answer is Right:**
Among the given options, Primaquine (C) is the only drug that acts as a tissue schizontocide, specifically targeting the hypnozoite form of Plasmodium vivax and Plasmodium ovale in the liver. This prevents relapse of vivax malaria.

**Why Each Wrong Option is Incorrect:**
1. Chloroquine (A) primarily targets the asexual schizonts in the red blood cells and is ineffective against hepatic hypnozoite form.
2. Artemisinin (B) is effective against asexual schizonts but is not a specific hypnozoite-targeting drug, so it doesn't prevent relapse.
3. Mefloquine (D) targets asexual schizonts but is not a specific hypnozoite-targeting drug, so it doesn't prevent relapse.

**Clinical Pearl:**
Primaquine is an important drug for preventing relapses of vivax and ovale malaria. However, due to its potential for causing hemolysis in glucose-6-phosphate dehydrogenase (G6PD)-deficient individuals, it is recommended to test for G6PD deficiency before administering primaquine. In G6PD-deficient patients, alternative therapies should be considered.