Which of the following psychostimulants acts centrally mainly by blocking adenosine receptors?

Correct Answer: B

Rationale: The correct answer is B: Caffeine. Caffeine acts centrally mainly by blocking adenosine receptors. Adenosine normally inhibits the release of neurotransmitters, but when adenosine receptors are blocked by caffeine, this inhibition is reduced, leading to increased alertness and wakefulness. Meridil (A), Amphetamine (C), and Sydnophen (D) do not primarily act by blocking adenosine receptors. Meridil is a sympathomimetic amine, Amphetamine is a psychostimulant that primarily acts by increasing the release of dopamine and norepinephrine, and Sydnophen is a stimulant drug.

Correct Answer: C

Rationale: The correct answer is C because hypertension is not a common consequence of neuroleptanalgesia. Droperidol and fentanyl are commonly used (A), and it can be combined with nitrous oxide for neuroleptanesthesia (B). Confusion and mental depression are potential adverse effects (D). The key is to recognize that hypertension is not a typical outcome of neuroleptanalgesia, making choice C the correct answer.

Correct Answer: D

Rationale: The correct answer is D: Apomorphine hydrochloride. Apomorphine is an emetic drug that acts centrally by stimulating dopamine receptors in the brain, particularly in the chemoreceptor trigger zone. This stimulation triggers the vomiting reflex. A: Ipecacuanha derivatives are peripheral emetics that work by irritating the stomach lining, leading to vomiting. B: Promethazine is an antiemetic drug that works by blocking dopamine receptors and has no emetic properties. C: Tropisetron is a serotonin receptor antagonist used to prevent nausea and vomiting, but it does not induce vomiting itself. In summary, apomorphine hydrochloride is the correct answer as it acts centrally to induce vomiting by stimulating dopamine receptors, whereas the other choices do not have central emetic action.

Correct Answer: B

Rationale: Verapamil is a calcium channel blocker and is not recommended in the initial stages of treating heart failure. ACE inhibitors and diuretics are commonly used to manage heart failure symptoms, while reduced salt intake is essential to prevent fluid retention. Verapamil can lead to negative effects on the heart in some heart failure patients, making it unsuitable for initial treatment. It is crucial to prioritize medications like ACE inhibitors and diuretics that have proven benefits in managing heart failure.

Correct Answer: D

Rationale: The correct answer is D: Potassium channel openers (Minoxidil). Potassium channel openers do not decrease myocardial oxygen requirement or increase myocardial oxygen delivery in angina. Nitrates and nitrite drugs, calcium channel blockers, and beta-adrenoceptor-blocking drugs all have mechanisms that achieve both of these effects. Nitrates and nitrite drugs dilate coronary arteries, increasing oxygen delivery, and decrease preload, decreasing oxygen demand. Calcium channel blockers reduce myocardial contractility and dilate coronary arteries. Beta-adrenoceptor-blocking drugs reduce heart rate and contractility, thus reducing oxygen demand. Potassium channel openers like minoxidil primarily act as vasodilators but do not have a direct effect on myocardial oxygen demand or delivery in angina.