Route of administration of dihydrotachysterol is:

Correct Answer: C

Rationale: The correct answer is C: Oral. Dihydrotachysterol is a form of vitamin D used to treat hypoparathyroidism. The oral route is chosen for its optimal absorption in the gastrointestinal tract. Intravenous (A) and subcutaneous (B) routes are not commonly used for dihydrotachysterol administration due to potential adverse effects and lack of significant benefits. Intranasal (D) administration is not suitable for dihydrotachysterol as it is not designed to be absorbed through the nasal mucosa.

Correct Answer: A

Rationale: The correct answer is A: Doxycycline, as it belongs to the tetracycline class of antibiotics. Tetracyclines inhibit bacterial protein synthesis by binding to the bacterial ribosome. Streptomycin (B) is an aminoglycoside, Clarithromycin (C) is a macrolide, and Amoxicillin (D) is a penicillin; these do not belong to the tetracycline class.

Correct Answer: B

Rationale: The correct answer is B because isoniazid inhibits the synthesis of mycolic acids, a crucial component of the cell wall of Mycobacterium tuberculosis. By blocking mycolic acid synthesis, isoniazid disrupts the integrity of the bacterial cell wall, leading to cell death. Choices A, C, and D are incorrect because isoniazid does not affect protein synthesis, RNA synthesis, or ADP synthesis. These processes are not targeted by isoniazid in its mechanism of action against tuberculosis.

Correct Answer: D

Rationale: Step-by-step rationale for choosing Pyrantel for nematodosis treatment: 1. Pyrantel is a well-known anthelmintic drug effective against roundworms. 2. It works by causing paralysis in the worms, leading to their expulsion from the body. 3. Pyrantel is commonly used to treat various nematode infections in humans. 4. Niclosamide is more effective against tapeworms, not nematodes. 5. Praziquantel is used for tapeworm and fluke infections, not specifically for nematodes. 6. Bithionol is an older drug with limited use and not commonly used for nematodosis treatment.

Correct Answer: A

Rationale: The correct answer is A: Leuprolide. Leuprolide is a gonadotropin-releasing hormone agonist that works by suppressing the release of gonadotropins, ultimately leading to decreased production of testosterone or estrogen. This is commonly used in the treatment of hormone-sensitive cancers, endometriosis, and certain reproductive disorders. Explanation for incorrect choices: B: Tamoxifen is a selective estrogen receptor modulator, not a gonadotropin-releasing hormone agonist. C: Flutamide is an androgen receptor antagonist used in the treatment of prostate cancer, not a gonadotropin-releasing hormone agonist. D: Anastrozole is an aromatase inhibitor that inhibits estrogen synthesis, not a gonadotropin-releasing hormone agonist.