Mechanism of action of calcitonin is:

Correct Answer: B

Rationale: The correct answer is B) Raises intracellular cAMP in osteoclasts. Calcitonin is a hormone produced by the thyroid gland that plays a key role in regulating calcium levels in the body. One of its main actions is to inhibit bone breakdown by osteoclasts. This is achieved by increasing intracellular cyclic adenosine monophosphate (cAMP) levels in osteoclasts, which leads to decreased bone resorption. Option A) Inhibits hydroxyapatite crystal formation, aggregation, and dissolution is incorrect because calcitonin does not directly affect the formation or dissolution of hydroxyapatite crystals. Option C) Activates bone resorption is incorrect because calcitonin actually inhibits bone resorption by osteoclasts. Option D) Inhibits macrophages is incorrect because calcitonin primarily targets osteoclasts in bone tissue, not macrophages. In an educational context, understanding the mechanism of action of calcitonin is important in the study of pharmacology, especially when learning about drugs that impact bone metabolism and calcium regulation. Knowing how calcitonin functions can help healthcare professionals make informed decisions when prescribing medications that affect bone health.

Correct Answer: D

Rationale: In this question, the correct answer is D) Mannitol (Osmitrol). Mannitol is an osmotic diuretic that acts by affecting tubular fluid composition in a non-receptor mediated fashion. It exerts its diuretic effect by creating an osmotic gradient that inhibits water reabsorption in the proximal tubule and loop of Henle. Now let's analyze why the other options are incorrect: A) Furosemide (Lasix) is a loop diuretic that acts by inhibiting the Na+/K+/2Cl- co-transporter in the thick ascending limb of the loop of Henle. It exerts its effect through a receptor-mediated mechanism. B) Acetazolamide (Diamox) is a carbonic anhydrase inhibitor that acts in the proximal convoluted tubule to prevent HCO3- reabsorption. It also works through a receptor-mediated mechanism. C) Triamterene (Dyrenium) is a potassium-sparing diuretic that acts on the distal convoluted tubule and collecting duct by blocking the epithelial sodium channel. This action is receptor-mediated. Educationally, understanding the different mechanisms of action of diuretics is crucial in pharmacology. Knowing how each drug affects tubular fluid composition helps in selecting the appropriate diuretic based on the clinical scenario, patient condition, and desired outcome. This knowledge is essential for healthcare professionals to make informed decisions regarding drug therapy for cardiovascular conditions.

Correct Answer: D

Rationale: In the context of pharmacology, understanding the mechanism of action of drugs is crucial for safe and effective prescribing. In the case of Amphotericin B, the correct answer is D) Alteration of cell membrane permeability. This antifungal medication works by binding to ergosterol in the fungal cell membrane, leading to the formation of pores that result in leakage of intracellular contents and ultimately cell death. Option A) Inhibition of cell wall synthesis is incorrect because this mechanism is typically associated with drugs like beta-lactam antibiotics targeting bacteria, not fungi. Option B) Inhibition of fungal protein synthesis is incorrect as Amphotericin B does not directly interfere with protein synthesis. Option C) Inhibition of DNA synthesis is also incorrect as this is not the primary mode of action of Amphotericin B. Educationally, grasping the mechanism of action of drugs like Amphotericin B aids in understanding how they exert their therapeutic effects and potential side effects. This knowledge is essential for healthcare professionals to make informed decisions when selecting and administering medications to patients, especially in cases of severe fungal infections where Amphotericin B is commonly used.

Correct Answer: C

Rationale: In this question about antimalarial drugs belonging to 8-aminoquinoline derivatives, the correct answer is C) Primaquine. Primaquine is classified as an 8-aminoquinoline derivative and is specifically used for the treatment of malaria caused by Plasmodium vivax and Plasmodium ovale. Now, let's analyze why the other options are incorrect: A) Doxycycline is a tetracycline antibiotic commonly used for treating various bacterial infections, not malaria caused by Plasmodium species sensitive to 8-aminoquinolines. B) Quinidine is an antiarrhythmic agent used to treat certain heart rhythm disorders, not malaria. D) Chloroquine is also an antimalarial drug, but it belongs to the 4-aminoquinoline class, not the 8-aminoquinoline derivatives as specified in the question. Educational context: Understanding the classification of antimalarial drugs is crucial in pharmacology to ensure the appropriate selection of medications for treating specific types of malaria infections. Knowing the distinct characteristics of different drug classes helps healthcare providers make effective and safe treatment decisions for patients with malaria.

Correct Answer: C

Rationale: In this question, the correct answer is C) Cyclophosphamide. Cyclophosphamide is an anticancer alkylating drug that is a derivative of chloroethylamine. Alkylating agents work by attaching alkyl groups to DNA, which prevents cell division and ultimately leads to cell death. Cyclophosphamide is commonly used in the treatment of various cancers, including leukemia, lymphoma, and solid tumors. Now, let's analyze why the other options are incorrect: A) Methotrexate: Methotrexate is not an alkylating agent. It is a type of antimetabolite drug that inhibits dihydrofolate reductase, interfering with DNA synthesis. B) Cisplatin: Cisplatin is a platinum-containing compound and not an alkylating agent. It works by forming cross-links in DNA, leading to cell death. D) Carmustine: Carmustine, also known as BCNU, is a nitrosourea compound and not an alkylating agent. It interferes with DNA replication and RNA transcription. Educationally, understanding the classification of anticancer drugs based on their mechanisms of action is crucial for pharmacology students and healthcare professionals. Knowing the specific properties of each drug helps in selecting the most appropriate treatment for different types of cancers and understanding potential side effects and interactions. This knowledge is essential for safe and effective medication management in clinical practice.