What is the main effect of mebendazole on helminths?

Mebendazole is primarily effective against helminths due to its ability to inhibit reproduction and cell growth. It works by binding to the beta-tubulin of helminths, disrupting the formation and function of microtubules. Microtubules are crucial for various cellular processes, including mitosis and transport within cells, leading to impaired cell division and growth in the parasites. This mechanism ultimately results in the death of the helminths as they are unable to reproduce effectively.

In contrast, the other options do not accurately describe the action of mebendazole. For instance, increasing blood flow to worms or enhancing nutrient absorption does not represent how anthelmintic agents operate; rather, their purpose is to incapacitate or kill the parasites. Additionally, while mebendazole can affect the metabolism of parasites, it does not primarily function by decreasing their metabolic rate in a direct sense. The main effect of mebendazole is clearly linked to its inhibitory action on reproduction and cell growth, making this the definitive answer.