Indicate the psychostimulant,which is a methylxanthine derivative:

Correct Answer: A

Rationale: The correct answer is A: Caffeine. Caffeine is a methylxanthine derivative known for its psychostimulant effects on the central nervous system. Methylxanthines are a class of compounds that include caffeine, theophylline, and theobromine, all of which act as stimulants. Sydnocarb (B) is a psychostimulant but not a methylxanthine derivative. Amphetamine (C) is a different class of psychostimulant compounds, and Meridil (D) is not a psychostimulant. Therefore, caffeine is the correct choice as the methylxanthine derivative with psychostimulant properties.

Correct Answer: B

Rationale: The correct answer is B: Flumazenil. Flumazenil is a specific benzodiazepine receptor antagonist that competitively inhibits the effects of benzodiazepines like midazolam, accelerating recovery from sedative actions. Naloxone (A) is used to reverse opioid effects, not benzodiazepines. Ketamine (C) is a dissociative anesthetic and not used to reverse benzodiazepine sedation. Fomepizole (D) is used in methanol or ethylene glycol toxicity, not for benzodiazepine reversal. Flumazenil is the specific antidote for benzodiazepine overdose.

Correct Answer: A

Rationale: Step-by-step rationale for choice A: 1. Metoclopramide is known to block dopamine receptors, making it a dopamine antagonist. 2. This action helps in treating nausea, vomiting, and gastrointestinal issues by enhancing motility. 3. Therefore, the statement that Metoclopramide is a potent dopamine antagonist is TRUE. Summary of other choices: B: FALSE - Incorrect, as Metoclopramide is indeed a dopamine antagonist. C: All - Incorrect, as not all the choices are correct. D: None of the above - Incorrect, as the correct answer is A.

Correct Answer: C

Rationale: The correct answer is C: An increase in vagal tone. In congestive heart failure, compensatory mechanisms aim to maintain cardiac output. An increase in ventricular end-diastolic volume helps to increase stroke volume. An increase in plasma catecholamines enhances contractility. Increased renin-angiotensin-aldosterone system activity helps to retain fluid and increase preload. However, an increase in vagal tone would actually decrease heart rate and cardiac output, worsening heart failure. Therefore, choice C is not a compensatory mechanism in congestive heart failure.

Correct Answer: A

Rationale: The correct answer is A because angina pectoris is defined as severe chest pain caused by insufficient blood supply to the heart due to coronary disease. This pain typically radiates to the left shoulder and arm due to reduced oxygen delivery to the heart muscle. Option B describes ventricular fibrillation, not angina. Option C refers to heart failure, not angina. Option D is incorrect as it includes unrelated conditions, making it an incorrect choice. Therefore, choice A is the correct answer for the definition of angina pectoris.