Medical Pharmacology Question Bank
Chapter 16: Antipsychotic Medications — Module 1 — Dopamine Pharmacology, Pathways & Classification
Tier: Core Concepts — Foundational Knowledge (22 questions)
1. All currently approved antipsychotic medications share a single common pharmacological target, even though they differ widely in their effects at other receptors. Which receptor is the primary target shared by all approved antipsychotics?
ANSWER: C
Rationale:
The dopamine D2 receptor is the single pharmacological target common to every currently approved antipsychotic. Whether an agent is a first-generation drug that blocks D2 potently or a second-generation drug that also engages serotonin and other receptors, meaningful antipsychotic effect requires action at D2. This is why D2 occupancy — not action at any other receptor — is the unifying concept that explains how this entire drug class works, and why understanding D2 pharmacology is the foundation for everything that follows in this module.
2. The original dopamine hypothesis of psychosis was first formulated in the early 1960s based on two observations: that drugs reducing dopamine signaling improved psychotic symptoms, and that dopamine-releasing drugs such as amphetamine could produce a paranoid psychotic state. In its simplest original form, what did this hypothesis propose was the cause of schizophrenia?
ANSWER: A
Rationale:
The original dopamine hypothesis proposed, in its simplest form, that schizophrenia resulted from too much dopamine activity, and that effective antipsychotics worked by reducing it. This was a unifying idea built from two converging clues: drugs that lowered dopamine signaling (such as chlorpromazine and reserpine) reduced psychosis, while drugs that raised dopamine release (such as amphetamine) could create a paranoid psychotic picture in healthy people. Understanding this starting point matters because the hypothesis was later refined into a more anatomically specific model, but the core insight — that dopamine activity is central to psychosis — still anchors how this drug class is understood.
3. Among first-generation antipsychotics, haloperidol is effective at doses of only a few milligrams per day, whereas chlorpromazine requires several hundred milligrams to achieve a comparable antipsychotic effect. When these drugs are described as "high-potency" versus "low-potency," what does the term potency refer to in this clinical context?
ANSWER: D
Rationale:
In antipsychotic pharmacology, potency refers specifically to the milligram dose needed to produce the antipsychotic effect — not to how strong the maximum effect can be. A high-potency agent such as haloperidol binds the D2 receptor tightly enough to work at single-digit milligram doses, while a low-potency agent such as chlorpromazine needs hundreds of milligrams for an equivalent effect. The clinical payoff of grasping this is that high-potency and low-potency agents can be equally effective at controlling psychosis; they simply differ in the dose required and, importantly, in their side-effect profiles.
4. The five dopamine receptors are all G protein-coupled receptors and are divided into two families based on how they signal inside the cell. The D1-like family (D1 and D5) couples to a stimulatory G protein (Gs). When a D1-like receptor is activated, what is the direct intracellular consequence?
ANSWER: B
Rationale:
The D1-like family (D1 and D5) couples to the stimulatory G protein Gs, which activates the enzyme adenylyl cyclase and raises intracellular cyclic AMP (cAMP) — a small signaling molecule that relays the receptor's message inside the cell. This is the defining feature that separates the D1-like family from the D2-like family. The concept matters because the two families have opposing effects on neuronal signaling: knowing that D1-like raises cAMP while D2-like lowers it is the foundation for understanding why blocking D2 receptors changes neuronal behavior in the circuits relevant to psychosis.
5. Dopamine neurons in the brain are organized into four major projection systems, and understanding these pathways is the key to predicting both the therapeutic effects and the side effects of antipsychotic drugs. Which of the following correctly lists the four major dopaminergic pathways?
ANSWER: E
Rationale:
The four major dopaminergic pathways are the mesolimbic, mesocortical, nigrostriatal, and tuberoinfundibular pathways. Each originates in a midbrain or hypothalamic nucleus and serves a distinct function, and the central principle of antipsychotic pharmacology is that D2 blockade affects all four simultaneously — producing the therapeutic effect in one pathway and characteristic side effects in the others. Committing this list to memory is worthwhile because nearly every benefit and adverse effect discussed in this drug class maps back to one of these four circuits.
6. The symptoms of schizophrenia are grouped into clinical dimensions. One dimension is described as "positive symptoms," where the word positive refers to the presence of abnormal experiences rather than to anything desirable. Which of the following best describes positive symptoms?
ANSWER: A
Rationale:
Positive symptoms are distortions or excesses of normal mental function — most prominently hallucinations (commonly auditory), delusions, and disorganized thinking or behavior. The term positive signals that something abnormal is present, not added benefit. This dimension matters clinically because positive symptoms are the most directly linked to mesolimbic dopamine overactivity and are, as a group, the symptoms most responsive to antipsychotic treatment.
7. Second-generation ("atypical") antipsychotics are distinguished from first-generation agents not only by a lower tendency to cause movement side effects but also by a characteristic pharmacological feature shared across the class. Which receptor action, combined with dopamine D2 activity, mechanistically defines most second-generation antipsychotics?
ANSWER: C
Rationale:
Most second-generation antipsychotics are defined mechanistically by combined dopamine D2 and serotonin 2A (5-HT2A) antagonism — or, for partial-agonist agents such as aripiprazole and cariprazine, by partial D2 agonism alongside 5-HT2A blockade. The relatively high ratio of 5-HT2A to D2 affinity is the property most associated with the class's lower movement-side-effect burden. Recognizing this pairing is the bridge to understanding why these agents behave differently from older drugs even when they reach similar levels of D2 blockade.
8. In the tuberoinfundibular pathway, dopamine released from the hypothalamus normally travels to the pituitary gland, where it continuously suppresses the secretion of prolactin (the hormone that stimulates milk production). What is the expected consequence when an antipsychotic blocks D2 receptors in this pathway?
ANSWER: B
Rationale:
Dopamine normally acts as a brake on prolactin release by tonically inhibiting the pituitary cells that secrete it. When an antipsychotic blocks D2 receptors in the tuberoinfundibular pathway, that brake is removed and prolactin rises — a state called hyperprolactinemia. The concept is clinically important because elevated prolactin produces recognizable effects such as galactorrhea (inappropriate milk production), menstrual irregularity, and sexual dysfunction, and unlike some other side effects it tends to persist rather than fade with continued treatment. Option A is the opposite of the true effect; removing dopamine's inhibition raises, not lowers, prolactin.
9. Many antipsychotics cause drowsiness, and some are notably more sedating than others. Blockade of which receptor is the primary mechanism responsible for antipsychotic-induced sedation?
ANSWER: D
Rationale:
Blockade of the histamine H1 receptor is the primary mechanism of antipsychotic-induced sedation, and it also contributes substantially to weight gain. Agents with high H1 affinity — such as clozapine, olanzapine, and quetiapine — are the most sedating in the class. This concept is practically useful because sedation can be either a liability or a tool: it may help with acute agitation, but persistent daytime drowsiness during maintenance treatment impairs functioning and adherence.
10. The nigrostriatal pathway carries dopamine to the part of the brain that controls movement, and it is the same pathway that degenerates in Parkinson disease. When an antipsychotic blocks D2 receptors here, it mimics a state of dopamine deficiency in the motor system. What clinical consequence does this produce?
ANSWER: B
Rationale:
Blocking D2 receptors in the nigrostriatal pathway recreates the functional state of dopamine deficiency in the brain's motor-control system, producing extrapyramidal symptoms (EPS) — drug-induced parkinsonism, acute dystonia (sustained muscle contractions), akathisia (motor restlessness), and, with long exposure, tardive dyskinesia. This connection between a specific pathway and a specific side effect is the core reasoning skill the module is building: each pathway's blockade predicts a particular clinical outcome. Option A maps to the tuberoinfundibular pathway, not the nigrostriatal pathway. Option C results from alpha-1 adrenergic blockade, a separate receptor action. Option D results from H1 (and metabolic) effects, not from nigrostriatal D2 blockade.
11. In schizophrenia, the mesocortical pathway (which projects to the prefrontal cortex) is characterized by too little dopamine activity rather than too much. This hypodopaminergic state is thought to underlie the negative symptoms and cognitive deficits of the illness. Given this, what is the expected effect of a standard D2-blocking antipsychotic on negative symptoms?
ANSWER: E
Rationale:
Because negative and cognitive symptoms arise from too little dopamine activity in the mesocortical pathway, a drug that blocks D2 receptors throughout the brain does not correct that deficit — and by further reducing dopamine signaling in an already underactive circuit, it may worsen these symptoms. This is a central reason negative symptoms respond poorly to standard antipsychotics, particularly older agents, and why they account for much of the long-term disability in schizophrenia.
12. Brain imaging studies that measure how much of the D2 receptor population a drug occupies have defined a useful therapeutic range. Antipsychotic response generally requires striatal D2 occupancy in the range of about 65 to 80 percent. What happens when occupancy is pushed above approximately 80 percent?
ANSWER: C
Rationale:
Above roughly 80 percent striatal D2 occupancy, extrapyramidal side effects climb steeply while antipsychotic benefit does not meaningfully increase — meaning the patient absorbs more harm for no added gain. This therapeutic window (about 65 to 80 percent) explains why pushing the dose ever higher is usually counterproductive and why dose optimization aims to stay above the efficacy threshold but below the side-effect threshold.
13. Serotonin normally suppresses dopamine release in several brain regions by acting on 5-HT2A receptors. Many second-generation antipsychotics block these 5-HT2A receptors. What is the expected effect of blocking 5-HT2A receptors on dopamine release in regions such as the prefrontal cortex and striatum?
ANSWER: A
Rationale:
Because serotonin acting at 5-HT2A receptors normally holds dopamine release in check, blocking those receptors removes the brake and disinhibits (increases) dopamine release. In the prefrontal cortex this partially restores the deficient mesocortical dopamine tone; in the striatum it raises the dopamine level enough to lessen the degree of effective D2 blockade, which raises the threshold for movement side effects. This is the mechanistic reason the newer agents tend to cause fewer extrapyramidal symptoms than older drugs at comparable D2 occupancy. Option E is biologically incorrect; neurons do not transform from one neurotransmitter identity into another in response to receptor blockade.
14. A patient started on a low-potency antipsychotic reports feeling dizzy and lightheaded when standing up quickly. This symptom reflects blockade of the alpha-1 adrenergic receptor, which normally helps maintain blood pressure when a person changes position. Which adverse effect does alpha-1 blockade most directly explain, and what is the main strategy to minimize it?
ANSWER: D
Rationale:
Alpha-1 adrenergic blockade impairs the reflex that maintains blood pressure on standing, producing orthostatic hypotension — the dizziness and lightheadedness the patient describes. The principal management strategy is to start at a low dose and titrate upward gradually, which allows partial tolerance to develop and limits symptomatic drops in pressure; this is especially important in elderly patients and those on antihypertensives.
15. In addition to receptors on the receiving (postsynaptic) neuron, D2 receptors also sit on the dopamine-releasing neuron itself, where they act as autoreceptors — sensors that detect dopamine in the synapse and signal the neuron to slow its own dopamine synthesis and release. What is the expected acute effect when an antipsychotic blocks these presynaptic D2 autoreceptors?
ANSWER: A
Rationale:
The presynaptic D2 autoreceptor is part of a negative-feedback loop: when it senses dopamine, it tells the neuron to make and release less. Blocking that autoreceptor removes the brake, so the neuron acutely releases more dopamine — partially counteracting the drug's blockade at postsynaptic receptors. This self-opposing effect is one reason the full antipsychotic response is delayed rather than immediate, even though receptor occupancy is achieved quickly. Option C is biologically incorrect, as neurons do not switch neurotransmitter identity.
16. When clinicians weigh first- versus second-generation antipsychotics, one major category of long-term harm is concentrated much more heavily in the second-generation group and has complicated the idea that newer agents are simply "better." Which group of adverse effects is most strongly associated with second-generation agents, particularly clozapine and olanzapine?
ANSWER: C
Rationale:
The metabolic adverse effects — weight gain, impaired glucose regulation, and abnormal lipids — are concentrated in the second-generation class and are most pronounced with clozapine and olanzapine. These effects are largely absent from most first-generation agents and represent a major long-term safety concern, which is why the early view of newer agents as categorically superior had to be tempered.
17. A young woman who began taking a high-potency first-generation antipsychotic several weeks ago develops milk production from her breasts and her menstrual periods have stopped. Using the pathway framework established earlier in this set, blockade of D2 receptors in which pathway best explains these new findings?
ANSWER: E
Rationale:
Galactorrhea (milk production) and amenorrhea (loss of menstrual periods) are the classic signs of elevated prolactin, and prolactin rises when D2 receptors in the tuberoinfundibular pathway are blocked — removing dopamine's normal suppression of prolactin secretion at the pituitary. This question applies the tuberoinfundibular concept built earlier to a new clinical presentation.
18. Two antipsychotics both achieve about 80 percent occupancy of striatal D2 receptors in a given patient. Drug 1 is a first-generation agent with negligible serotonin activity; Drug 2 is a second-generation agent with strong 5-HT2A blockade in addition to its D2 activity. Based on the mechanisms established earlier in this set, which statement best predicts their movement side effects?
ANSWER: B
Rationale:
At equal striatal D2 occupancy, the agent with strong 5-HT2A blockade (Drug 2) is expected to cause fewer extrapyramidal symptoms. This follows directly from two concepts built earlier: 5-HT2A blockade disinhibits striatal dopamine release, which partially offsets the D2 blockade and raises the threshold for movement side effects. The question asks the student to combine the occupancy concept with the serotonin-dopamine interaction.
19. A patient with schizophrenia has been treated with two different antipsychotics, each at an adequate dose for an adequate duration, yet continues to have prominent hallucinations and delusions. This pattern of persistent positive symptoms despite adequate dopamine D2 blockade defines a recognized clinical category. Which category is this, and which agent has the strongest evidence base for it?
ANSWER: D
Rationale:
Persistent positive symptoms despite adequate D2 occupancy across adequate trials defines treatment-resistant schizophrenia, and clozapine has the strongest evidence base for this group. This question extends the positive-symptom concept from earlier: positive symptoms are usually the most treatment-responsive dimension, so their persistence after adequate blockade is what marks resistance.
20. A patient on a high-potency first-generation antipsychotic appears to have little facial expression and reduced spontaneous movement and seems unmotivated. On examination, the reduced movement is found to be drug-induced parkinsonism (a movement side effect), and after the dose is lowered the apparent lack of motivation improves substantially. Negative symptoms that arise from an identifiable, reversible cause like this are best described as which of the following?
ANSWER: A
Rationale:
Negative symptoms that arise from an identifiable, reversible cause — here, drug-induced parkinsonism producing reduced movement and an appearance of low motivation — are secondary negative symptoms, and they improved once the cause was addressed. This question applies the earlier concept that standard antipsychotics can worsen the functional state of the mesocortical system, and asks the student to distinguish a remediable mimic from the intrinsic deficit. Option E misuses "tardive," which refers specifically to late-emerging movement disorders such as tardive dyskinesia, not to reversible drug-induced parkinsonism mimicking avolition.
21. A patient started on an antipsychotic reports marked daytime drowsiness, has gained weight, and also complains of dry mouth, constipation, and blurred vision. Using the receptor concepts established earlier in this set, this combination of effects is best explained by strong blockade of which two receptors?
ANSWER: C
Rationale:
Drowsiness and weight gain point to histamine H1 blockade, while dry mouth, constipation, and blurred vision are the classic anticholinergic effects of muscarinic M1 blockade. Together they identify an agent with strong H1 and M1 activity. This question asks the student to combine two receptor-to-effect relationships built earlier and read them backward from a clinical picture to the receptor profile.
22. A large real-world comparative trial (CATIE) directly compared a mid-potency first-generation antipsychotic, perphenazine, against several second-generation agents and found that perphenazine performed comparably to the newer drugs on the main outcome of all-cause discontinuation. Using the classification concepts established earlier in this set, what is the best general lesson to draw from this finding?
ANSWER: B
Rationale:
The best general lesson is that the first- versus second-generation distinction is a useful starting point for pharmacological reasoning but not a guaranteed hierarchy: a well-chosen first-generation agent can perform comparably to newer drugs, so agent selection should be individualized rather than driven by a default class preference. This applies the earlier concepts of potency and of the FGA/SGA definitions to a real comparative result. Option C draws the opposite unjustified conclusion, dismissing second-generation agents entirely.