A morbidly obese person visits the local bariatric (weight loss) clinic seeking a pill that will help shed weight. The physician prescribes dextroamphetamine. In addition to causing its expected centrally mediated anorexigenic (appetite-suppressant) effects, it causes a host of peripheral adrenergic effects that, for some patients, can prove fatal. The main mechanism by which dextroamphetamine or amphetamines in general, cause their peripheral autonomic effects is

Correct Answer: C

Rationale: Rationale for Correct Answer (C): Dextroamphetamine causes peripheral adrenergic effects by displacing, releasing, intraneuronal NE. Amphetamines disrupt the storage and release of NE from intraneuronal vesicles, leading to an increase in synaptic NE levels. This excess NE can stimulate adrenergic receptors in the periphery, causing adverse effects like hypertension, tachycardia, and potentially fatal outcomes. Summary of Incorrect Choices: A: Activating MAO would increase NE breakdown, not cause peripheral adrenergic effects. B: Blocking NE reuptake would increase NE levels in the synapse, not intraneuronally, leading to central effects. D: Enhancing NE synthesis would not directly lead to peripheral adrenergic effects, as it would require release and action at the synapse.

Correct Answer: D

Rationale: Adrenaline is contraindicated in hypertension because it can worsen high blood pressure and increase the risk of cardiovascular events. Adrenaline's vasoconstrictive effects can further elevate blood pressure in individuals with hypertension, potentially leading to severe complications. Therefore, it is crucial to avoid administering adrenaline in patients with hypertension to prevent adverse cardiovascular outcomes. Summary: - A: Adrenaline is indicated in cardiac arrest to improve cardiac output. - B: Adrenaline is indicated in acute bronchial asthma to relax bronchial smooth muscles. - C: Adrenaline is indicated in anaphylactic shock to reverse severe allergic reactions. - D (Correct): Adrenaline is contraindicated in hypertension due to its vasoconstrictive effects.

Correct Answer: C

Rationale: Monoamine oxidase enzyme (MAO) is responsible for the degradation of neurotransmitters like adrenaline. MAO breaks down adrenaline into inactive metabolites, regulating its levels in the body. This process is crucial for maintaining neurotransmitter balance. Choice A is incorrect because MAO does not activate adrenaline. Choice B is incorrect as MAO is not involved in adrenaline synthesis. Choice D is incorrect as MAO does not degrade acetylcholine, but rather neurotransmitters like serotonin, dopamine, and adrenaline.

Correct Answer: D

Rationale: The correct answer is D: Atropine does not produce bronchoconstriction. Atropine is an anticholinergic drug that blocks the action of acetylcholine, leading to increased heart rate (A), stimulation of the respiratory center (B), and mydriatic effect (C). Bronchoconstriction is not a pharmacological effect of atropine because it actually helps dilate the bronchi, making it a useful treatment in cases of bronchospasm.

Correct Answer: D

Rationale: The correct answer is D because acidification of urine actually increases the excretion of amphetamine. Step 1: Amphetamine is an indirect acting sympathomimetic, which means it stimulates the release of norepinephrine. Step 2: It has prominent CNS action by increasing the release of dopamine and norepinephrine, leading to effects like increased alertness and euphoria. Step 3: Chronic use of amphetamine can indeed lead to addiction due to its reinforcing properties and impact on the brain's reward system. Therefore, D is incorrect as acidification of urine does not decrease amphetamine excretion; instead, it can enhance excretion by increasing its solubility in urine.