**Question:** Chemoprohylaxis of chloroquine includes -

A. Proguanil
B. Pyrimethamine
C. Sulfadoxine
D. Mefloquine

**Core Concept:** Chloroquine is an antimalarial drug used to prevent and treat malaria infection caused by Plasmodium species. Chemoprophylaxis refers to the use of drugs to prevent disease. The correct combination for chloroquine chemoprophylaxis depends on the Plasmodium species prevalent in the region.

**Why the Correct Answer is Right:**

The correct answer, **C. Sulfadoxine**, is used in combination with pyrimethamine (Fansidar) for chloroquine chemoprophylaxis. This combination is effective against Plasmodium falciparum, the most common cause of severe malaria worldwide, particularly in sub-Saharan Africa, Asia, and South America.

**Why Each Wrong Option is Incorrect:**

A. **Proguanil (Paludrine)** is used for malaria prophylaxis but is ineffective against Plasmodium falciparum. It is recommended for areas with Plasmodium vivax and Plasmodium ovale infections.

B. **Pyrimethamine (Daraprim)** is an antifolate drug used in combination with sulfadoxine (Fansidar) for chloroquine-resistant Plasmodium falciparum malaria. However, it is not a standalone chemoprophylactic agent.

D. **Mefloquine (Lariam)** is used for prophylaxis in areas with Plasmodium vivax and Plasmodium ovale infections, but it does not cover Plasmodium falciparum, which is the primary cause of severe malaria.

**Core Concept:** Sulfadoxine is an antifolate drug, while pyrimethamine is an antifolate drug that inhibits dihydrofolate reductase enzyme in Plasmodium parasites. When used together, they effectively combat chloroquine-resistant Plasmodium falciparum malaria.

**Why Each Wrong Option is Incorrect:**

A. Proguanil is not effective against chloroquine-resistant Plasmodium falciparum malaria. It is used primarily for Plasmodium vivax and Plasmodium ovale infections.

B. Mefloquine is effective against Plasmodium vivax and Plasmodium ovale but is not recommended for Plasmodium falciparum malaria, which is the primary cause of severe malaria.

D. Pyrimethamine is effective against Plasmodium vivax and Plasmodium ovale but is not recommended for Plasmodium falciparum malaria, which is the primary cause of severe malaria.

**Clinical Pearl:** Combining sulfadoxine and pyrimethamine is essential for chloroquine-resistant Plasmodium falciparum malaria prevention. The correct combination is known as Fansidar (s