Question

Which class of antimalarial drugs is responsible for radical cure by killing exo-erythrocytic forms?

• A. 8-Aminoquinolines
• B. Artemisinin compounds
• C. Biguanides
• D. Phenanthrene methanols

Hint:

In malaria, some Plasmodium species (P. vivax and P. ovale) form dormant liver-stage parasites called hypnozoites (exo-erythrocytic forms).

Answer 1

The Correct Option is A

Step 1: What is a radical cure in malaria?
In malaria caused by Plasmodium vivax and P. ovale, the parasite can form dormant liver stages called hypnozoites. These can reactivate months or years later and cause relapse. Radical cure means eliminating these hypnozoites to prevent relapse.

Step 2: Exo-erythrocytic forms explained.
After a mosquito bite, the parasite first goes to the liver (exo-erythrocytic phase) and develops there before entering red blood cells. Hypnozoites are dormant exo-erythrocytic forms. Only drugs that can kill these liver-stage parasites can achieve radical cure.

Step 3: Evaluate Option 1 - 8-Aminoquinolines.
8-Aminoquinolines like Primaquine and Tafenoquine are the ONLY class of antimalarials that can kill hypnozoites (dormant liver stages). This makes them the only drugs capable of radical cure. They are used after chloroquine to prevent relapse in P. vivax and P. ovale malaria. This is the correct answer.

Step 4: Evaluate Option 2 - Artemisinin compounds.
Artemisinins are very effective against blood-stage parasites (erythrocytic forms) and reduce parasite load rapidly. They do not kill hypnozoites in the liver.

Step 5: Evaluate Options 3 and 4.
Biguanides (like proguanil) act on erythrocytic forms and as causal prophylaxis. Phenanthrene methanols (like lumefantrine) act on blood-stage parasites only. Neither affects hypnozoites.

Step 6: Conclusion.
8-Aminoquinolines are the only class that kills exo-erythrocytic (liver) forms, achieving radical cure.
Answer: Option (1) — 8-Aminoquinolines