MAC Pharmacology of Substances 2 — Questions and Answers
Question 1: Which neurotransmitter system is PRIMARILY responsible for the reinforcing effects of most addictive substances?
- Serotonin in the raphe nuclei
- Dopamine in the mesolimbic pathway (Correct answer)
- GABA in the cerebellum
- Acetylcholine in the striatum
Correct answer: Dopamine in the mesolimbic pathway
The mesolimbic dopamine pathway, particularly projections from the ventral tegmental area to the nucleus accumbens, mediates reward and reinforcement for most addictive substances.
Question 2: A client reports that after stopping benzodiazepines abruptly, they experienced seizures. This is because benzodiazepines act as:
- GABA-A receptor positive allosteric modulators (Correct answer)
- NMDA receptor antagonists
- Opioid receptor agonists
- Dopamine reuptake inhibitors
Correct answer: GABA-A receptor positive allosteric modulators
Benzodiazepines enhance GABA-A receptor activity, and abrupt cessation causes CNS hyperexcitability due to rebound, which can manifest as seizures.
Question 3: Naltrexone reduces alcohol cravings primarily by blocking:
- GABA receptors in the cortex
- Endogenous opioid receptors that mediate alcohol's rewarding effects (Correct answer)
- Serotonin 5-HT3 receptors in the gut
- Adenosine receptors in the brainstem
Correct answer: Endogenous opioid receptors that mediate alcohol's rewarding effects
Naltrexone blocks mu-opioid receptors, thereby attenuating the endorphin-mediated euphoria and reward that contributes to alcohol craving.
Question 4: Which of the following is the MOST accurate description of the half-life of THC metabolites in heavy cannabis users?
- 2–6 hours, cleared within 24 hours
- 12–24 hours, cleared within 3 days
- Several days to weeks due to fat solubility (Correct answer)
- Exactly 72 hours in all users
Correct answer: Several days to weeks due to fat solubility
THC is highly lipophilic and accumulates in fatty tissue, causing metabolites to be detectable in urine for weeks in heavy chronic users.
Question 5: Cocaine's primary mechanism of action involves:
- Increasing GABA release in the limbic system
- Blocking reuptake of dopamine, norepinephrine, and serotonin (Correct answer)
- Stimulating mu-opioid receptors directly
- Opening voltage-gated calcium channels
Correct answer: Blocking reuptake of dopamine, norepinephrine, and serotonin
Cocaine inhibits the reuptake transporters for dopamine, norepinephrine, and serotonin, increasing synaptic concentrations of all three monoamines.
Question 6: A client prescribed methadone for opioid use disorder asks why they need a higher dose than the one used for pain management. The counselor should understand that methadone's analgesic duration is approximately:
- Same as its duration for suppressing opioid withdrawal (24–36 hours)
- 6–8 hours, much shorter than its withdrawal-suppression duration (Correct answer)
- 48–72 hours, longer than its anti-withdrawal duration
- Identical regardless of the clinical indication
Correct answer: 6–8 hours, much shorter than its withdrawal-suppression duration
Methadone's analgesic effect lasts 4–8 hours, while its ability to suppress opioid withdrawal lasts 24–36 hours, so pain patients may need more frequent dosing.
Question 7: Which substance produces withdrawal symptoms that can be life-threatening due to autonomic instability and seizures, similar to alcohol?
- Heroin
- Amphetamine
- Barbiturates (Correct answer)
- Cannabis
Correct answer: Barbiturates
Barbiturate withdrawal, like alcohol withdrawal, can cause severe autonomic instability and potentially fatal seizures due to CNS rebound hyperexcitability.
MAC Pharmacology of Substances 2
Which neurotransmitter system is PRIMARILY responsible for the reinforcing effects of most addictive substances?