Which of the following anthelmintic acts as a cholinergic agonist in the nematodes and causes spastic paralysis of the worms?

Correct Answer: B

Rationale: Step-by-step rationale for why Pyrantel pamoate (choice B) is the correct answer: 1. Pyrantel pamoate is a cholinergic agonist that acts on nematodes by stimulating nicotinic receptors, leading to spastic paralysis of the worms. 2. Its mechanism of action involves depolarizing the neuromuscular junction, causing sustained muscle contraction in the parasites. 3. This spastic paralysis makes the worms lose their ability to maintain attachment to the host's intestine, facilitating their expulsion from the body. 4. Piperazine (choice A) works by blocking the response of the worm's muscle cells to acetylcholine, causing flaccid paralysis. 5. Mebendazole (choice C) and Albendazole (choice D) are benzimidazole anthelmintics that inhibit microtubule formation, leading to impaired glucose uptake and energy depletion in the parasites, not acting as cholinergic agonists.

Correct Answer: B

Rationale: The correct answer is B: Testosterone. Dutasteride is a 5-alpha reductase inhibitor used to treat BPH by reducing DHT levels. Testosterone is converted to DHT by the enzyme 5-alpha reductase, so combining dutasteride with testosterone can potentially increase the risk of side effects related to low DHT levels. Tamsulosin is an alpha blocker and does not directly interact with dutasteride. Sildenafil is a phosphodiesterase inhibitor used for erectile dysfunction and does not have a known interaction with dutasteride. Hydrochlorothiazide is a diuretic and is unlikely to interact with dutasteride.

Correct Answer: C

Rationale: The correct answer is C: Nitroglycerin should be avoided in a patient taking sildenafil because both drugs can cause a significant drop in blood pressure leading to severe hypotension, syncope, or even cardiovascular collapse. Nitroglycerin is a potent vasodilator, and when combined with sildenafil (a phosphodiesterase type 5 inhibitor), the additive vasodilatory effects can result in dangerous hypotension. A: Amlodipine and B: Diltiazem are calcium channel blockers that are commonly used in combination with sildenafil for the treatment of hypertension and angina. They work through different mechanisms and do not have a significant interaction with sildenafil. D: Metoprolol is a beta-blocker that can be safely used with sildenafil. It helps in reducing heart rate and blood pressure, and its combination with sildenafil can have a beneficial effect in patients with angina.

Correct Answer: C

Rationale: Furosemide inhibits the Na+K+/2Cl- transporter in the renal tubular cell specifically in the thick ascending limb of the loop of Henle. This leads to decreased reabsorption of sodium, potassium, and chloride ions, resulting in increased excretion of water and electrolytes. The other choices, Na+K+ ATPase (A), Na+/Cl- transporter (B), and Na+H+ antiporter (D), are not the primary target of furosemide in the kidney and do not lead to the same diuretic effect.

Correct Answer: D

Rationale: The correct answer is D: Hydrochlorothiazide. When combined with potassium sparing diuretics like spironolactone, hydrochlorothiazide can lead to hyperkalemia due to the additive effects on potassium levels. This combination requires close monitoring to prevent dangerous elevations in potassium levels. Furosemide (A) is a loop diuretic and does not typically interact with spironolactone in the same way. Captopril (B) is an ACE inhibitor, not a diuretic, and does not directly affect potassium levels. Verapamil (C) is a calcium channel blocker and does not interact with spironolactone in terms of potassium levels.