What is the mechanism of action for diethylcarbamazine?

Diethylcarbamazine (DEC) primarily functions by immobilizing microfilariae, which are the juvenile forms of filarial parasites found in the bloodstream. This immobilization is crucial because it allows the host's immune system to more effectively clear these parasites from circulation. The drug acts to alter the surface structure of the microfilariae, leading to increased susceptibility to phagocytosis and ultimately aiding in their removal by immune cells. This mechanism of action is particularly significant in the treatment of conditions caused by filarial infections, such as lymphatic filariasis and onchocerciasis.

While other options discuss various mechanisms of action employed by different drugs, they do not pertain to diethylcarbamazine. Enhancing immune response and inhibiting RNA synthesis are relevant to different types of treatments, and disrupting microtubule function characterizes other anthelmintics such as benzimidazoles. Therefore, immobilization of microfilariae is the correct and specific mechanism through which diethylcarbamazine exerts its therapeutic effects.