An antihelmenthic drug that is effective against blood fluke, liver fluke, lung fluke and cysticercus is :
Antihelminthic drugs vary by target. Praziquantel is known for treating schistosomiasis and tapeworms, including cysticercus. It works by causing muscle spasms and tegumental damage. Bithionol is used for liver flukes but not others. Triclabendazole is for liver flukes too. Praziquantel should be effective against all the mentioned parasites here. The other options are more specific. So the correct answer is praziquantel.
**Core Concept**
This question tests knowledge of broad-spectrum antihelminthic agents. **Praziquantel** is a key drug effective against various flukes (e.g., *Schistosoma*, *Clonorchis*, *Paragonimus*) and cestodes (e.g., *Taenia solium* cysticercus). Its mechanism involves tegumental calcium influx and muscle hypercontraction.
**Why the Correct Answer is Right**
**Praziquantel** acts on all listed parasites by disrupting calcium homeostasis in their teguments, leading to paralysis and immune clearance. It is the first-line treatment for schistosomiasis, paragonimiasis, and cysticercosis. Its efficacy spans trematodes (flukes) and cestodes (tapeworms), making it uniquely broad-spectrum among antihelminthics.
**Why Each Wrong Option is Incorrect**
**Option A: Bithionol** – Effective only against liver flukes (*Clonorchis*, *Opisthorchis*), not blood/lung flukes or cysticercus.
**Option B: Triclabendazole** – Targeted at liver flukes (*Fasciola*, *Clonorchis*), with no activity against other flukes or cestodes.
**Option C: Niclosamide** – Active solely against tapeworms, not flukes.
**Clinical Pearl / High-Yield Fact**
Praziquantel is the **gold standard** for all fluke infections and cysticercosis. Remember: "Praziquantel = Praz for **P**arasites like **Flukes** and **Tapeworms**." Avoid confusion with flukicides like triclabendazole, which lack cestode activity.
**Correct Answer: C. Praziquantel**