A 31-year-old man comes to the physician because of several months of recurrent abdominal pain and diarrhea. Six months ago, he traveled to Lake Superior for a fishing trip with his friends, during which they often ate their day's catch for dinner. Physical examination shows pallor. Laboratory studies show macrocytic anemia with eosinophilia. A peripheral blood smear shows megaloblasts and hypersegmented neutrophils. A cestode infection is suspected and a drug is prescribed that kills cestodes by inducing uncontrollable muscle spasm in the parasite. The drug prescribed for this patient most likely acts by which of the following mechanisms of action?

Increased calcium influx into the sarcoplasm

Increased potassium efflux from the sarcoplasm

Increased sodium efflux from the sarcoplasm

Phosphorylation of adenosine diphosphate

Blockade of myosin binding sites

An 18-year-old boy from Rajasthan weighing 50 kg is diagnosed with mixed P . vivax and P . falciparum malaria. What is the appropriate treatment regimen on day 2?

Artesunate 50 mg (4 tablets) + Sulfadoxine/ pyrimethamine ( 750/37.5 mg ) (2 tablets) + Primaquine 2.5 mg ( 6 tablets)

Artesunate 50 mg (4 tablets) + Primaquine 2.5 mg ( 6 tablets)

Artesunate 50 mg (4 tablets) + Primaquine 7.5 mg (6 tablets)

Artesunate 50 mg (4 tablets) + Sulfadoxine/ pyrimethamine ( 750/37.5 mg ) (2 tablets) + Primaquine 7.5 mg ( 6 tablets)

Artesunate 50 mg (4 tablets) only

Which of the following statements about Ciclesonide is incorrect?

Oral candidiasis is common with its use.

It is a prodrug activated by bronchial esterase.

It has comparable efficacy to other inhalational corticosteroids.

It has fewer side effects than other inhalational corticosteroids.

It has low systemic bioavailability due to extensive first-pass metabolism.

Anthelmintics for USMLE Step 3: High-Yield Pharmacology Lessons

Anthelmintic Classes - Worms, Be Gone!

Benzimidazoles (e.g., Albendazole, Mebendazole): Inhibit microtubule synthesis.
- Broad-spectrum: nematodes (roundworms, pinworms, hookworms) & cestodes (tapeworms).
Praziquantel: Increases calcium permeability, causing paralysis & death.
- Treats cestodes (tapeworms) & trematodes (flukes like Schistosoma).
Pyrantel Pamoate: Depolarizing neuromuscular blocker, causing paralysis.
- Effective for pinworms, roundworms, and hookworms.

Anthelmintic Drugs: Classes and Mechanisms of Action

⭐ High-Yield: Albendazole is the drug of choice for neurocysticercosis (pork tapeworm larvae in the brain). Co-administer with corticosteroids to reduce inflammation from dying cysticerci.

Drugs for Nematodes - Roundworm Roundup

Benzimidazoles (Albendazole, Mebendazole)
- MOA: Inhibit microtubule polymerization by binding to β-tubulin, disrupting cellular transport and energy metabolism.
- Spectrum: Broad. Effective for Ascaris lumbricoides (giant roundworm), Trichuris trichiura (whipworm), Enterobius vermicularis (pinworm), and hookworms (Ancylostoma, Necator).
- 📌 Mnemonic: Worms get bent out of shape.
Ivermectin
- MOA: Potentiates glutamate-gated chloride channels in invertebrate nerve and muscle cells → hyperpolarization and paralysis.
- Spectrum: Drug of choice for Strongyloides stercoralis and Onchocerca volvulus (River Blindness).
Pyrantel Pamoate
- MOA: Depolarizing neuromuscular blocking agent → spastic paralysis of worms.
- Spectrum: Pinworms and roundworms. Available over-the-counter.

⭐ For neurocysticercosis (a CNS infection with tapeworm larvae), Albendazole is used with corticosteroids to manage the inflammatory response to dying cysts.

Drugs for Trematodes & Cestodes - Flatworm Finishers

Praziquantel: The primary drug for flukes (trematodes) and tapeworms (cestodes).
- MoA: Increases cell membrane permeability to Ca²⁺, causing spastic paralysis, dislodgement, and death of the worm.
- 📌 Praziquantel paralyzes the worms.

Indication	Drug of Choice	Notes
Schistosoma, Clonorchis	Praziquantel	Treats most fluke infections.
Taenia solium (tapeworm)	Praziquantel	For intestinal stage.
Neurocysticercosis	Albendazole	Use with corticosteroids.

Praziquantel: Molecular Targets, Phenotypes, and Outcomes

High‑Yield Points - ⚡ Biggest Takeaways

Benzimidazoles (e.g., albendazole) inhibit parasitic microtubule synthesis. They are broad-spectrum agents for most nematode (roundworm) infections.

Praziquantel increases calcium permeability, causing spastic paralysis of trematodes (flukes) and cestodes (tapeworms). It is the drug of choice for schistosomiasis.

Ivermectin activates glutamate-gated chloride channels, leading to flaccid paralysis. It is first-line for onchocerciasis and strongyloidiasis.

Pyrantel pamoate is a depolarizing neuromuscular blocker causing paralysis.

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Anthelmintics