The following sympathomimetic drug is a catecholamine:

Correct Answer: D

Rationale: Step-by-step rationale for why D (Isoprenaline) is the correct answer: 1. Isoprenaline is a catecholamine because it has a catechol structure, which consists of a benzene ring with two hydroxyl groups. 2. Catecholamines are a class of neurotransmitters that include dopamine, norepinephrine, and epinephrine. 3. Isoprenaline acts as a non-selective beta-adrenergic agonist, stimulating both beta-1 and beta-2 adrenergic receptors. 4. Its pharmacological effects include increased heart rate, bronchodilation, and vasodilation. Summary of why other choices are incorrect: A. Ephedrine is a sympathomimetic drug but is not a catecholamine as it lacks the catechol structure. B. Phenylephrine is a sympathomimetic drug that acts as an alpha-adrenergic agonist,

Correct Answer: B

Rationale: The correct answer is B: Hyoscine. Muscarinic receptors can be stimulated by Pilocarpine, Acetylcholine, and Neostigmine, as they are known agonists of muscarinic receptors. Hyoscine, also known as scopolamine, is an antagonist of muscarinic receptors, blocking their stimulation. This makes it the exception among the listed drugs.

Correct Answer: C

Rationale: The correct answer is C: Hypotension. Chronic tobacco smoking typically causes vasoconstriction, leading to increased blood pressure rather than hypotension. Peripheral vascular disease (A), cardiac arrhythmias (B), and increased gastric secretion (D) are common effects of chronic tobacco smoking due to the harmful impact on blood vessels, heart function, and gastrointestinal system.

Correct Answer: D

Rationale: Propranolol is a non-selective beta-blocker which primarily affects the heart. Bronchodilation is not a common effect of propranolol due to its non-selectivity for beta-2 receptors in the lungs. Therefore, choice D is the correct answer. Choices A, B, and C are correct because propranolol typically causes negative inotropic effect (reduced force of heart contraction), negative chronotropic effect (slowing of heart rate), and slowing of A-V conduction (delay in electrical signal between atria and ventricles), respectively.

Correct Answer: C

Rationale: Certainly! Bethanechol is a muscarinic agonist that specifically targets the bladder and bowel smooth muscles, improving their tone and contractility. It is used for conditions like atonic bowel or bladder dysfunction. Clonidine is an alpha-2 adrenergic agonist, Chlorpromazine is a typical antipsychotic, and Ephedrine is a sympathomimetic amine used for decongestion and bronchodilation. These medications do not have the same mechanism of action or target as Bethanechol and are not indicated for atonic bowel or bladder issues.