**Core Concept:** Albendazole is an anthelmintic drug commonly used in the treatment of various helminth infections, including ascariasis, a type of roundworm infection caused by Ascaris lumbricoides. It works by inhibiting beta-tubulin, a crucial protein for parasite cell division.

**Why the Correct Answer is Right:** In the treatment of ascariasis, albendazole is administered at a dose of 400 mg as a single oral dose. The drug exerts its effect by inhibiting the function of beta-tubulin, a key component in the parasite's cell division process. This results in the impaired growth and reproduction of Ascaris lumbricoides, eventually leading to the death of the parasites and their expulsion from the body.

**Why Each Wrong Option is Incorrect:**

A. 400 mg twice daily (twice the correct dose): This is incorrect because albendazole's effect is dose-dependent, and administering the drug twice daily would result in excessive toxicity to the patient without significantly improving the treatment outcome.

B. 200 mg twice daily: This is incorrect too, as it is also higher than the recommended dose and might cause side effects without improving treatment efficacy.

C. 200 mg dose: This is wrong because 200 mg is half the recommended dose, making it insufficient for effective treatment of ascariasis.

D. Oral route: Although the correct answer states the route of administration (oral), the actual dose remains crucial for effective treatment, as explained above.

**Clinical Pearl:** The proper dosing of albendazole is crucial for effective treatment of ascariasis. In this case, the correct answer states the route of administration (oral), while emphasizing the importance of the 400 mg single dose for optimal efficacy and safety.

**Correct Answer:** A. 400 mg as a single oral dose