Select the side-effect characteristic for non-selective beta2-adrenomimics:

Correct Answer: B

Rationale: The correct answer is B: Tachycardia. Non-selective beta2-adrenomimics stimulate both beta1 and beta2 adrenergic receptors, leading to increased heart rate (tachycardia) due to beta1 receptor activation. A: Depression of the breathing centre is not a side effect of non-selective beta2-adrenomimics. C: Peripheral vasoconstriction is more commonly associated with alpha-adrenergic agonists, not beta2-adrenomimics. D: Dry mouth is not a common side effect of beta-adrenergic stimulation.

Correct Answer: C

Rationale: Amrinone inhibits breakdown of cAMP by inhibiting phosphodiesterase enzyme in vascular smooth muscle. This leads to increased cAMP levels, causing vasodilation. Digoxin, dobutamine, and dopamine have no direct effect on cAMP breakdown in vascular smooth muscle. Digoxin increases intracellular calcium, dobutamine is a beta-adrenergic agonist, and dopamine acts on dopamine receptors.

Correct Answer: C

Rationale: Step 1: Beta-adrenoceptor-blocking drugs primarily work by blocking the beta-adrenergic receptors in the body. Step 2: By blocking these receptors, these drugs decrease heart rate, blood pressure, and contractility of the heart muscle. Step 3: These hemodynamic effects lead to decreased myocardial oxygen requirements at rest and during exercise, providing beneficial effects. Step 4: Choice C is correct as it accurately describes the main mechanism and beneficial effects of beta-adrenoceptor-blocking drugs. Step 5: Choices A, B, and D are incorrect as they do not accurately describe the primary mechanism or effects of beta-adrenoceptor-blocking drugs.

Correct Answer: D

Rationale: The correct answer is D because all the listed drug groups influence cerebral blood flow. Ca-channel blockers dilate blood vessels, enhancing cerebral perfusion. GABA derivatives can modulate blood flow by affecting neurotransmission. Vinca minor derivatives like vincamine can improve cerebral circulation. Therefore, all choices have a direct impact on cerebral flow, making D the correct answer.

Correct Answer: A

Rationale: The correct answer is A: Radioiodines in the body emit mainly β radiations. This is because radioiodines typically decay by β- decay, releasing β particles. β radiation consists of electrons or positrons, which are emitted during the decay process. This type of radiation is commonly observed with radioiodines. Option B is incorrect because γ radiation is a type of electromagnetic radiation emitted by the nucleus, not by radioiodines in this case. Option C is incorrect because radioiodines predominantly emit β radiation, not an equal amount of β and γ. Option D is incorrect because radioiodines do emit radiation, particularly β radiation, and therefore are not completely safe in terms of radiation exposure.