Each of the following parasympathomimetics is paired with an appropriate therapeutic use EXCEPT:

Correct Answer: D

Rationale: The correct answer is D because parathion is not a parasympathomimetic drug; it is an organophosphorus insecticide. Physostigmine (A), Neostigmine (B), and Edrophonium (C) are all parasympathomimetics used for their respective therapeutic purposes. Physostigmine is used in glaucoma to reduce intraocular pressure, Neostigmine is used to treat postoperative urinary retention by improving bladder emptying, and Edrophonium is used in the diagnosis of myasthenia gravis by temporarily improving muscle strength. In contrast, parathion is not a medication but a toxic substance used in insecticides, and it does not have any therapeutic use as a parasympathomimetic drug.

Correct Answer: A

Rationale: The correct answer is A: Excessive salivation. Atropine is an anticholinergic medication that blocks the action of acetylcholine, leading to decreased secretions including saliva. Excessive salivation is not an adverse effect but rather a therapeutic effect of atropine. Choices B, C, and D are incorrect because retention of urine, sinus tachycardia, and constipation are known adverse effects of atropine due to its anticholinergic properties.

Correct Answer: D

Rationale: The correct answer is D: Tachycardia. Anticholinergic medications block the action of acetylcholine, leading to increased heart rate (tachycardia) by inhibiting the parasympathetic nervous system. Excessive salivation (choice A) is a cholinergic effect, not anticholinergic. Bradycardia (choice B) is not consistent with anticholinergic side effects. Diarrhea and colic (choice C) are more commonly associated with cholinergic, not anticholinergic, effects.

Correct Answer: B

Rationale: Correct Answer: B Rationale: 1. Prazosin and phentolamine both antagonize alpha1-receptors, leading to vasodilation and decreased blood pressure. 2. Both drugs are competitive antagonists, competing with norepinephrine at alpha1-receptors. 3. However, phentolamine causes reflex tachycardia due to its non-selective alpha-adrenergic blockade, unlike prazosin. 4. Therefore, the statement that both cause the same degree of tachycardia is incorrect based on their pharmacological differences.

Correct Answer: D

Rationale: Step-by-step rationale: 1. Isoprenaline is a beta-adrenergic agonist. 2. It directly stimulates beta adrenoceptors, leading to effects like increased heart rate. 3. Isoprenaline causes bronchodilation by relaxing bronchial smooth muscles. 4. It also causes vasodilation, leading to decreased blood pressure. 5. Isoprenaline does not have a direct effect on intestinal motility, making option D incorrect. Summary: Option D is incorrect as isoprenaline does not increase intestinal motility. Options A, B, and C are correct as isoprenaline directly stimulates beta adrenoceptors, relaxes bronchial smooth muscles, and decreases blood pressure, respectively.