Which of the following antianginal agents is a calcium channel blocker?

Correct Answer: D

Rationale: Nifedipine is a calcium channel blocker used as an antianginal agent to treat angina by dilating blood vessels and reducing the workload of the heart. It specifically blocks L-type calcium channels in vascular smooth muscle. Nitroglycerin is a nitrate that works by dilating blood vessels but does not block calcium channels. Dipyridamole is a platelet aggregation inhibitor. Minoxidil is a direct vasodilator that opens potassium channels, not calcium channels. Therefore, the correct answer is D (Nifedipine).

Correct Answer: B

Rationale: The correct answer is B: Angina pectoris. Thyroid hormones can increase cardiac output and oxygen demand, potentially leading to angina. A: Increases in basal metabolic rate is a common therapeutic effect of thyroid hormones. C: Tremors may occur as a sign of hyperthyroidism but not a direct side effect of thyroid hormone therapy. D: Exopthalmos is a clinical sign of Graves' disease, not a direct side effect of thyroid hormone therapy.

Correct Answer: A

Rationale: The correct answer is A: TRUE. Mifepristone is a progesterone receptor antagonist that can be used for both contraception and abortion. As a contraceptive, it prevents implantation by altering the endometrium. As an abortifacient, it induces uterine contractions and softens the cervix, leading to expulsion of the embryo. Incorrect choices: B: FALSE - Mifepristone is indeed used for contraception and abortion, so this statement is inaccurate. C: None - This choice does not provide any information or contribute to the discussion, making it irrelevant. D: All of the above - This is incorrect as not all choices are true. Mifepristone being used for contraception and abortion does not mean that all choices are correct.

Correct Answer: A

Rationale: The correct answer is A because an immediate allergy reaction, also known as a type I allergic reaction, typically occurs within minutes to about an hour after exposure to an antigen. This rapid onset is characteristic of type I hypersensitivity reactions mediated by IgE antibodies. It involves the release of histamine and other inflammatory mediators from mast cells and basophils, leading to symptoms such as hives, itching, swelling, and in severe cases, anaphylaxis. Choice B is incorrect because it describes a delayed allergic reaction, which usually takes hours to days to develop. Choice C is incorrect as it describes type II hypersensitivity reactions involving IgM or IgG antibodies, not type I reactions. Choice D is incorrect as it describes type III hypersensitivity reactions involving antigen-antibody complexes, not type I reactions.

Correct Answer: B

Rationale: The correct answer is B because antivitamins are substances that interfere with the absorption, metabolism, or utilization of vitamins, preventing them from exerting their typical metabolic effects. This definition directly aligns with the concept of antivitamins. Option A is incorrect because it describes vitamins themselves, not antivitamins. Option C describes enzymes, not antivitamins. Option D refers to coenzymes, which are necessary for enzyme function, but it does not accurately define antivitamins. Thus, B is the correct choice.