All of these drugs reduce intestinal peristalsis EXCEPT:

Correct Answer: B

Rationale: The correct answer is B: Cisapride. Cisapride is a prokinetic agent that enhances gastrointestinal motility, therefore it does not reduce intestinal peristalsis. Loperamide (A) is an anti-diarrheal drug that acts by slowing down intestinal peristalsis. Methyl cellulose (C) is a bulk-forming laxative that can help regulate bowel movements by increasing stool bulk and promoting peristalsis. Magnesium aluminium silicate (D) is an antacid that can potentially slow down intestinal transit time by absorbing water in the intestine. So, B is the correct answer as it is the only drug that does not reduce intestinal peristalsis.

Correct Answer: C

Rationale: The correct answer is C: Amyl nitrite, inhalant. Amyl nitrite is a short-acting drug used for the treatment of angina pectoris and cyanide poisoning. It works quickly to dilate blood vessels and relieve chest pain. Nitroglycerin ointment and sustained-release tablets have longer durations of action, making them not short-acting. Sustac is not a nitrate or nitrite drug, so it is an incorrect choice. Overall, the rapid onset and short duration of action of amyl nitrite make it the correct choice for a short-acting nitrate/nitrite drug.

Correct Answer: C

Rationale: The correct answer is C: Phenylephrine. Phenylephrine is a synthetic vasoconstrictor that acts by stimulating adrenergic receptors, specifically alpha-adrenergic receptors, leading to vasoconstriction. Noradrenaline (A) and adrenaline (B) are endogenous catecholamines that also have vasoconstrictive effects but are not synthetic. Angiotensinamide (D) is not a synthetic vasoconstrictor and acts through a different mechanism involving the renin-angiotensin system. In summary, Phenylephrine is the correct choice as it is a synthetic vasoconstrictor with adrenomimetic effects, while the other options do not fit this description.

Correct Answer: D

Rationale: Thyroid stimulating hormone (TSH) regulates all the mentioned functions. 1. A: TSH stimulates iodine uptake by thyroid follicular cells for thyroid hormone synthesis. 2. B: TSH promotes the biosynthesis of iodothyroglobulin, a precursor of thyroid hormones. 3. C: TSH triggers the release of thyroid hormones into the bloodstream. Therefore, the correct answer is D as TSH regulates all these processes essential for thyroid hormone production and release. Other choices are incorrect as they do not encompass all the functions regulated by TSH.

Correct Answer: C

Rationale: Step-by-step rationale for why choice C (Progesterone) is correct: 1. Progesterone is a major natural progestin produced by the corpus luteum in the ovaries. 2. It plays a crucial role in the menstrual cycle and maintaining pregnancy. 3. Estradiol (choice A), Estron (choice B), and Estriol (choice D) are all estrogens, not progestins. 4. Estradiol is a predominant estrogen in premenopausal women, while Estron and Estriol are less potent estrogens. 5. Therefore, the correct answer is choice C, Progesterone, as it is the primary natural progestin in the body.