Which of the following agents belongs to psychostimulants?

Correct Answer: A

Rationale: The correct answer is A: Meridil. Psychostimulants are substances that can increase alertness, attention, and energy levels. Meridil, also known as methylphenidate, is a commonly prescribed psychostimulant used to treat conditions like ADHD. Camphor (B) is a topical analgesic, Piracetam (C) is a nootropic agent, and Pantocrin (D) is a herbal supplement with purported energy-boosting properties. Therefore, only Meridil (A) fits the classification of a psychostimulant among the choices provided.

Correct Answer: D

Rationale: The correct answer is D: All of the above. Nitrous oxide, Desflurane, and Sevoflurane are all inhaled anesthetics known for their rapid onset and recovery. Nitrous oxide is rapid due to its low blood-gas solubility, while Desflurane and Sevoflurane are quick-acting because of their low solubility and fast elimination from the body. Therefore, all three options meet the criteria of having rapid onset and recovery. The other choices are incorrect because they do not fully encompass all the anesthetics that exhibit these characteristics.

Correct Answer: C

Rationale: The correct answer is C: Pirenzepin. M1-cholinoblockers specifically target the M1 muscarinic acetylcholine receptor subtype. Pirenzepin is a selective M1 receptor antagonist, making it the appropriate choice. A: Cimetidine and B: Ranitidine are H2-receptor antagonists used for treating gastric acid-related conditions. D: Omeprazole is a proton pump inhibitor that works by reducing stomach acid production. These drugs do not target the M1 muscarinic receptor subtype, so they are not the correct choices for M1-cholinoblockers.

Correct Answer: B

Rationale: Step 1: Heparin is a medication with poor oral bioavailability, meaning it is not effectively absorbed when taken orally. Step 2: For heparin to be effective, it needs to be administered via injection or infusion to reach therapeutic levels. Step 3: Therefore, the statement that heparin is effective when administered orally is false. Summary: Choice B is correct because heparin's efficacy is not achieved through oral administration. Choices A, C, and D are incorrect because they do not acknowledge the pharmacokinetics of heparin.

Correct Answer: C

Rationale: Rationale: Lidocaine is the drug of choice for acute treatment of ventricular tachycardias due to its fast onset of action and minimal negative inotropic effects. It works by stabilizing cell membranes and reducing automaticity in the ventricular tissue. Flecainide (A) and Sotalol (B) are contraindicated in ventricular tachycardias due to their potential to worsen arrhythmias. Verapamil (D) is a calcium channel blocker and is not effective for treating ventricular tachycardias.