Side effect of vitamin D3 is:

Correct Answer: B

Rationale: The correct answer is B: Metastatic calcifications. Vitamin D3 can lead to hypercalcemia, causing calcium to deposit in soft tissues like blood vessels and kidneys, leading to metastatic calcifications. Choice A is incorrect because vitamin D deficiency, not excess, causes defective bone mineralization. Choice C is incorrect as vitamin D toxicity primarily affects calcium levels, not the liver. Choice D is incorrect as nephrolithiasis is more commonly associated with excess intake of calcium supplements, not vitamin D3.

Correct Answer: B

Rationale: The correct answer is B: Enlarged uptake of the drug by a microorganism. This is incorrect because mechanisms of bacterial resistance involve reducing the uptake of the drug (choice D), modifying the drug's target (choice C), and actively transporting the drug out of the microorganism or hydrolyzing it with enzymes (choice A). Enlarged uptake would actually make the bacteria more susceptible to the antimicrobial agent, not resistant.

Correct Answer: D

Rationale: The correct answer is D. Sulfonamides inhibit folic acid synthesis, which is essential for the growth of bacteria, Chlamydia, Actinomyces, and some protozoa. This mechanism makes them effective against all the mentioned microorganisms. Choice A is incorrect because it does not include protozoa. Choice B is incorrect because sulfonamides are effective against Actinomyces. Choice C is incorrect because sulfonamides are not effective against all protozoa.

Correct Answer: B

Rationale: The correct answer is B: Diloxanide. Diloxanide is the drug of choice for treating the asymptomatic intestinal form of amebiasis because it acts specifically against the trophozoites in the lumen of the intestine without affecting the cysts. Chloroquine (A) is used for malaria, emetine (C) is used for invasive amebiasis, and doxycycline (D) is an antibiotic not typically used for amebiasis.

Correct Answer: B

Rationale: The correct answer is B: Doxorubicin. Doxorubicin is an antibiotic commonly used in cancer chemotherapy to treat various types of cancer. It works by inhibiting DNA and RNA synthesis in cancer cells, leading to cell death. Cytarabine (A) is an antimetabolite used in leukemia treatment, not an antibiotic for cancer chemotherapy. Gentamycin (C) is an aminoglycoside antibiotic used for bacterial infections, not cancer treatment. Etoposide (D) is a topoisomerase inhibitor used in cancer chemotherapy but is not classified as an antibiotic.