Correct Answer: C

Rationale: Rifampin (Rifadin) achieves a therapeutic action against both intracellular and extracellular tuberculosis organisms by inhibiting the synthesis of RNA. This action interferes with bacterial RNA synthesis, leading to the suppression of protein synthesis in the bacteria, ultimately causing their death. Option A is incorrect because rifampin is primarily metabolized in the liver, but this is not how it exerts its bactericidal effects. Option B is incorrect as rifampin does not bind to acetylcholine. Option D is also incorrect as rifampin does not cause phagocytosis.

Correct Answer: C

Rationale: The correct answer is C. Oral contraceptives can be less effective when taken with certain antibiotics due to potential drug interactions that may reduce contraceptive efficacy. It is crucial for patients to be aware of this to consider additional contraceptive measures when prescribed antibiotics. Choice A is incorrect because while oral contraceptives are highly effective when taken correctly, they are not 100% foolproof. Choice B is incorrect as oral contraceptives may take some time to reach their full effectiveness after starting. Choice D is also incorrect as taking oral contraceptives with food does not significantly affect their efficacy.

Correct Answer: D

Rationale: Osteosarcoma is a type of bone cancer that can be found in any bone but is most commonly located in the long bones of the legs. While it is more prevalent in children and young adults, it can also occur in older individuals like the 60-year-old male patient in this case. Early diagnosis is crucial for a better prognosis in osteosarcoma cases. Therefore, all the statements provided are true regarding osteosarcoma, making option D the correct answer. Option A is accurate as osteosarcoma is more common in children and young adults. Option B is correct as early diagnosis improves the prognosis. Option C is accurate as osteosarcoma is frequently located in the leg bones.

Correct Answer: C

Rationale: Ivermectin (Stromectol) is commonly used to treat parasitic infections, particularly Strongyloides stercoralis. This parasitic infection is known to respond well to Ivermectin therapy. Entamoeba histolytica causes amoebiasis and is typically treated with antiprotozoal drugs like metronidazole, not Ivermectin. Giardia lamblia is a protozoan parasite causing giardiasis, which is usually treated with medications like metronidazole or tinidazole, not Ivermectin. Plasmodium falciparum is a malaria-causing parasite and is not treated with Ivermectin but with antimalarial medications like chloroquine or artemisinin-based combination therapies.

Correct Answer: C

Rationale: Rifampin (Rifadin) achieves a therapeutic action against both intracellular and extracellular tuberculosis organisms by inhibiting the synthesis of RNA. This action interferes with bacterial RNA synthesis, leading to the suppression of protein synthesis in the bacteria, ultimately causing their death. Option A is incorrect because rifampin is primarily metabolized in the liver, but this is not how it exerts its bactericidal effects. Option B is incorrect as rifampin does not bind to acetylcholine. Option D is also incorrect as rifampin does not cause phagocytosis.