The principal central nervous system effect of the opioid analgesics with affinity for a mu receptor is:

Correct Answer: D

Rationale: The correct answer is D: All of the above. Opioid analgesics with affinity for the mu receptor exert their principal central nervous system effects through various mechanisms. 1. Analgesia: Opioids bind to mu receptors, inhibiting pain transmission in the CNS. 2. Respiratory depression: Stimulation of mu receptors in the brainstem suppresses the respiratory drive. 3. Euphoria: Activation of mu receptors in the limbic system can induce feelings of euphoria. Therefore, all these effects are collectively produced by opioids with mu receptor affinity. Other choices are incorrect because they do not encompass the comprehensive range of central nervous system effects associated with this class of analgesics.

Correct Answer: D

Rationale: The correct answer is D: Fluoxetine. Fluoxetine is a selective serotonin reuptake inhibitor (SSRI) because it specifically targets the reuptake of serotonin in the brain, leading to increased levels of serotonin available for neurotransmission. Phenelzine (A) is a monoamine oxidase inhibitor, Desipramine (B) is a tricyclic antidepressant, and Maprotiline (C) is a tetracyclic antidepressant. These medications work through different mechanisms than SSRIs and do not specifically target serotonin reuptake. Therefore, they are not classified as SSRIs.

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: B

Rationale: The correct answer is B: Antipsychotic drugs. Narco- and glue sniffing involve inhalation of substances for their mind-altering effects. Antipsychotic drugs are not typically abused for recreational purposes due to their sedative effects and lack of euphoria. Stimulants (choice A), psychedelics (choice C), and sedative drugs (choice D) are commonly misused for their psychoactive properties, leading to addiction and harmful effects on the body. Therefore, antipsychotic drugs do not fit the profile of substances commonly associated with narco- and glue sniffing.

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.