Hypnotic drugs should:

Correct Answer: C

Rationale: The correct answer is C because hypnotic drugs are primarily used to induce drowsiness and promote sleep. They help with insomnia and encourage the onset and maintenance of sleep. This is achieved by affecting the brain's neurotransmitters and promoting relaxation. Options A and D are incorrect as hypnotic drugs are not intended to specifically reduce anxiety, exert a calming effect, or prevent mood swings in patients with bipolar affective disorders. Option B is incorrect as hypnotic drugs do not induce an absence of sensation; that would be more characteristic of anesthetics.

Correct Answer: B

Rationale: Levodopa is the precursor of dopamine as it is converted into dopamine in the brain. Bromocriptine is a dopamine agonist, not a precursor. Selegiline is a MAO-B inhibitor that helps preserve dopamine, not a precursor. Amantadine is an antiviral drug with unclear mechanisms regarding dopamine production. Therefore, B is the correct answer.

Correct Answer: C

Rationale: The correct answer is C: Meperidine. Meperidine is commonly used in obstetric labor due to its rapid onset of action and short duration, making it suitable for managing acute pain during labor without affecting the fetus adversely. Fentanyl (A) is also a potent opioid analgesic, but its rapid onset and short duration make it more suitable for surgical procedures. Pentazocine (B) is a partial opioid agonist-antagonist and is not commonly used in obstetric labor due to its limited efficacy in managing severe pain. Buprenorphine (D) is a partial agonist with a long duration of action and is typically used for opioid maintenance therapy rather than acute pain management during labor.

Correct Answer: B

Rationale: The correct answer is B: Tramadol. Tramadol is a mixed (opioid/non-opioid) agent as it acts on opioid receptors and inhibits the reuptake of serotonin and norepinephrine. This dual mechanism provides both opioid and non-opioid effects. Paracetamol (A) is a non-opioid analgesic, sodium valproate (C) is an anticonvulsant, and butorphanol (D) is a mixed opioid agonist-antagonist but not typically used as a tick mixed agent.

Correct Answer: A

Rationale: Rationale: MAO-A is more selective for depression because it primarily metabolizes serotonin and norepinephrine, neurotransmitters implicated in mood regulation. MAO-B mainly metabolizes dopamine. Choices B and C are incorrect because MAO-B is not as closely associated with depression, and MAO-C is a fictitious enzyme.