Indication for administration of histamine H1 antagonists is:

Correct Answer: D

Rationale: Rationale: Histamine H1 antagonists are commonly used to prevent or treat allergic reactions like rhinitis and urticaria due to their antihistaminic properties. They are also effective in managing symptoms of motion sickness and vestibular disturbances by inhibiting histamine release in the brain. Moreover, these antagonists are recommended for treating nausea and vomiting in pregnancy, commonly known as "morning sickness," as they help alleviate these symptoms by blocking histamine receptors. Therefore, the correct answer is D, as histamine H1 antagonists are indicated for all the mentioned conditions. Choices A, B, and C are incorrect as they individually do not encompass the full range of indications for histamine H1 antagonists.

Correct Answer: A

Rationale: The correct answer is A: TRUE. The Coronary Primary Prevention Trial (CPPT) indeed showed that treatment with a lipid-lowering drug reduced the risk of death due to coronary heart disease. This conclusion is based on the findings and results of the study, which have been scientifically validated. Choice B is incorrect because the CPPT did demonstrate the effectiveness of lipid-lowering drugs in reducing coronary heart disease mortality. Choice C, All, and Choice D, None, are also incorrect as they do not accurately reflect the specific outcome of the CPPT. Thus, the correct answer is A because it aligns with the established evidence and results of the study.

Correct Answer: D

Rationale: Rationale: D is the correct answer because the parathyroid hormone (PTH) actually increases calcium reabsorption and decreases phosphate excretion in the kidneys, not the other way around. PTH acts on the kidneys to enhance calcium reabsorption and decrease phosphate reabsorption, leading to increased serum calcium levels and decreased serum phosphate levels. Choices A, B, and C are correct statements about PTH, highlighting its role in regulating calcium and phosphate levels in the body.

Correct Answer: D

Rationale: The correct answer is D because magnesium is not a physiological calcium agonist. Magnesium acts as a physiological calcium antagonist, meaning it competes with calcium for binding sites and can inhibit calcium influx into cells. This is important for various cellular functions, including muscle contraction, nerve conduction, and blood clotting. Choices A, B, and C are correct statements about magnesium. Magnesium is indeed mainly an intracellular cation and is the fourth most abundant cation in the body. The recommended dietary amounts of magnesium are around 350-400 mg per day, and the common causes of magnesium deficiency include diet, alcoholism, diarrhea, malabsorption, diabetes mellitus, and certain medications like diuretics and aminoglycosides.

Correct Answer: D

Rationale: The correct answer is D: Collecting duct. Amiloride acts as a potassium-sparing diuretic by blocking sodium channels in the collecting duct, preventing reabsorption of sodium and water. This leads to increased excretion of sodium and water, while retaining potassium. This mechanism specifically targets the collecting duct, making choice D the correct answer. Choices A, B, and C are incorrect because amiloride does not act on the proximal convoluted tubule, ascending thick limb of the loop of Henle, or distal convoluted tubule.