Facts read from nursingworld.org and 1 more · last checked Nov 7, 2026
Domain I carries 22% of the scored items, 33 questions. It asks why a drug does what it does: which receptor explains a side effect, which enzyme explains an interaction, which circuit explains a symptom. Choosing the drug for a given patient is tested in diagnosis and treatment.
Practice questions
60 questions written to the PMHNP-BC outline; each choice is explained once you pick.
Pathophysiology: medical illness that presents as, or worsens, psychiatric illness.
General pharmacology: contraindications, interactions and adverse effects of the non-psychiatric drugs your patients also take.
Psychopharmacology: pharmacokinetics, pharmacodynamics, extrapyramidal symptoms and neuroleptic malignant syndrome.
The brain: neurodevelopment, neuroanatomy and neurophysiology.
Psychopharmacogenomics: gene–drug interactions and heritability.
Skill: advanced physical assessment.
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Six mechanisms that decide answers
Extrapyramidal effects follow a clock. Acute dystonia appears within hours to days of starting or raising a high-potency antipsychotic, akathisia within days to weeks, drug-induced parkinsonism over weeks, tardive dyskinesia after months or years. The timing in a stem is often the clue to which one it is.
NMS and serotonin toxicity look alike only at a glance. NMS develops over days after dopamine blockade (or abrupt withdrawal of a dopamine agonist), with lead-pipe rigidity, slowed reflexes and a high CK. Serotonin toxicity comes on within hours of a serotonergic combination, with clonus, hyperreflexia and agitation (Hunter criteria).
Long half-lives set washout times. Fluoxetine and its metabolite norfluoxetine linger for weeks; its label requires at least 5 weeks off fluoxetine before an MAOI starts.
Lithium skips the liver. It is not metabolized by CYP enzymes and leaves through the kidneys, so its interactions are renal: thiazides, NSAIDs and ACE inhibitors raise levels (lithium labeling).
Estrogen lowers lamotrigine. Estrogen-containing contraceptives cut lamotrigine levels by about half, and levels rise in the pill-free week (lamotrigine labeling); pregnancy lowers them too.
Psychiatric symptoms can be medical. Thyroid disease, B12 deficiency, HIV, syphilis, hepatic encephalopathy and delirium all present with mood, anxiety or psychotic symptoms. A first episode warrants a basic work-up before the label sticks.
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Pharmacogenomic results, read narrowly
The outline names gene–drug interactions, and stems may hand you a lab report. CPIC’s 2023 guideline on antidepressants gives dosing advice by CYP2D6 and CYP2C19 phenotype, and FDA’s table of pharmacogenomic biomarkers lists which psychotropic labels carry gene information. A genotype changes a starting dose or steers you away from a drug; it does not predict whether the drug will work, and a panel is not needed before every prescription.
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15 questions on mechanisms and neurobiology
0 / 15 answered15 questions
Tap an option: why each one is right or wrong appears under it.
Scientific Foundation · 22%
A 42-year-old taking tranylcypromine for treatment-resistant depression presents with new-onset confusion, diaphoresis, tachycardia, and myoclonus. Which recently added medication is most likely responsible for this acute presentation?
With an MAOI, pseudoephedrine risks a hypertensive crisis with severe headache, not myoclonus with altered mental status.
This antibiotic has no MAO-inhibiting or serotonergic activity, unlike linezolid.
Acetaminophen has no serotonergic or pressor action and is a safe analgesic with MAOIs.
Dextromethorphan inhibits serotonin reuptake, and with an MAOI it can cause serotonin syndrome: confusion, sweating, tachycardia, and myoclonus.
A patient being treated for severe depression asks why their medication requires several weeks to achieve maximal efficacy despite reaching steady-state plasma concentrations in days. What is the primary biological mechanism responsible for this specific delay?
Reuptake blockade is immediate, but the clinical effect follows slower adaptive changes: receptor regulation, second-messenger signaling, and gene expression that support neuroplasticity.
Antidepressants raise synaptic monoamines rather than exhaust them; depletion would predict worsening.
Fat distribution shapes half-life and washout, not the lag between steady-state levels and response.
Active metabolites reach steady state with the parent drug, so metabolism does not explain a delay that outlasts steady state.
A 31-year-old gained 9 kg in the first 4 months of olanzapine treatment and reports constant hunger. Antagonism at which pair of receptors is most responsible for this weight gain?
Muscarinic and alpha-1 blockade explain constipation, dry mouth, and orthostasis, not hunger.
Neither D2 nor alpha-2 blockade is the appetite mechanism; alpha-2 antagonism is how mirtazapine raises monoamine release.
Combined H1 and 5-HT2C antagonism raises appetite and is the main driver of weight gain with olanzapine and clozapine, the agents strongest at both receptors.
D2 blockade drives EPS and prolactin, and 5-HT1A partial agonism belongs to weight-sparing agents such as aripiprazole.
A 35-year-old with schizophrenia responds well to haloperidol 5 mg daily, which corresponds to about 70% striatal D2 occupancy. To speed recovery, a colleague proposes raising the dose to reach about 85% occupancy. What is the most likely result?
Antipsychotic response plateaus near 65 to 70% striatal D2 occupancy, while extrapyramidal symptoms climb steeply above about 80%.
More D2 blockade at the pituitary raises prolactin further; it does not lower it.
Higher occupancy does not cause acute loss of efficacy through desensitization.
Efficacy does not keep rising beyond the therapeutic occupancy window; the extra blockade buys side effects.
A 34-year-old veteran with PTSD reports intrusive trauma memories triggered by contextual cues and shows impaired fear extinction on a laboratory task. Imaging shows reduced gray matter volume in one limbic structure. Dysfunction of which structure best explains the contextual memory disturbance?
The locus coeruleus supplies norepinephrine for arousal and hypervigilance; it is a brainstem nucleus, not a limbic memory structure.
The ventral striatum serves reward and motivation, not contextual memory.
The amygdala drives fear acquisition and expression and is hyperactive in PTSD, but it does not store context.
The hippocampus encodes context and signals when a cue is safe in the current setting, so its dysfunction fits cue-triggered intrusions and poor extinction; smaller hippocampal volume is a replicated PTSD finding.
A 55-year-old man with no psychiatric history began prednisone 60 mg daily for sarcoidosis 2 weeks ago. He now sleeps 2 hours a night, has grandiose business plans, pressured speech, and irritability. He is fully oriented with intact attention. Which diagnosis is most likely?
Manic symptoms starting within weeks of high-dose prednisone in a man with no mood history meet criteria for medication-induced bipolar and related disorder.
Schizoaffective disorder needs at least 2 weeks of psychosis without mood symptoms, which he has never had.
Delirium requires disturbed attention and awareness; he is oriented with intact attention.
Bipolar I requires that the episode not be attributable to a substance or medication; the timing points to prednisone.
A 38-year-old woman who is a known CYP2D6 poor metabolizer stopped paroxetine because of side effects and needs a new antidepressant. Which agent depends least on CYP2D6 for its clearance?
Nortriptyline depends on CYP2D6, and levels rise sharply in poor metabolizers.
CYP2D6 converts venlafaxine to desvenlafaxine, so poor metabolizers accumulate the parent drug.
Vortioxetine is metabolized mainly by CYP2D6, and its label caps the dose at 10 mg in poor metabolizers.
Desvenlafaxine is cleared mainly by conjugation and the kidneys, with minimal CYP2D6 involvement, so genotype does not change its dosing.
A 24-year-old woman develops acute psychosis, agitation, and memory loss over two weeks, followed by seizures and orofacial dyskinesias. An ovarian teratoma is found. Which mechanism underlies this condition?
Prion disease causes rapidly progressive dementia with myoclonus over months and is not antibody-mediated.
Ischemia produces focal deficits in a vascular distribution, not an autoimmune neuropsychiatric syndrome.
IgG antibodies against the GluN1 subunit internalize NMDA receptors and cause hypofunction, producing psychosis, memory loss, seizures, and autonomic instability.
Dopamine excess is the model for primary psychosis; this encephalitis is an antibody attack on glutamate receptors.
A patient on antipsychotic therapy develops tremor and rigidity, then later galactorrhea. Which pathway-to-effect pairing is correct?
This reverses the pathways: the nigrostriatal tract governs movement, and prolactin is controlled by the tuberoinfundibular tract.
Mesolimbic blockade is the antipsychotic effect on positive symptoms, and nigrostriatal blockade causes movement effects, not prolactin rise.
D2 blockade in the nigrostriatal tract produces tremor and rigidity, and in the tuberoinfundibular tract it releases prolactin from dopamine inhibition, causing galactorrhea.
Akathisia is a nigrostriatal extrapyramidal effect, and the mesocortical tract has no role in prolactin.
A patient with treatment-resistant depression is found to carry an MTHFR gene mutation. The PMHNP understands this mutation contributes to depression primarily through which mechanism?
Serotonin transporter variation is a separate gene (SLC6A4) unrelated to folate metabolism.
MTHFR makes L-methylfolate, which supports the BH4 cofactor needed for serotonin, dopamine, and norepinephrine synthesis; reduced activity limits monoamine production and raises homocysteine.
MTHFR acts on folate metabolism, not on monoamine breakdown.
Tryptophan hydroxylase is downstream and depends on BH4; the variant does not alter the enzyme itself.
Predominant alogia, avolition, and flat affect in schizophrenia are linked to which pathway abnormality?
Low dopamine signaling in the mesocortical tract to the prefrontal cortex is linked to negative and cognitive symptoms such as alogia, avolition, and flat affect.
Noradrenergic overactivity drives arousal and anxiety rather than alogia and avolition.
Excess 5-HT2A signaling is linked to hallucinations, as with psychedelic drugs, not to deficit symptoms.
Mesolimbic overactivity is tied to positive symptoms such as hallucinations and delusions.
A 33-year-old with PTSD is starting prolonged exposure therapy, which relies on fear extinction learning. Which structure provides the top-down inhibition of amygdala fear responses that extinction depends on?
The nucleus accumbens handles reward and motivation, not inhibition of fear responses.
Extinction recall depends on the ventromedial prefrontal cortex inhibiting the amygdala; it is hypoactive in PTSD, and exposure therapy retrains this top-down control.
The locus coeruleus drives noradrenergic arousal, which feeds fear rather than suppressing it.
The paraventricular nucleus starts the HPA stress response through CRH; it does not inhibit fear.
A patient with schizoaffective disorder stabilized on quetiapine is started on carbamazepine. Two weeks later, psychotic symptoms recur. Which mechanism best explains this?
Autoinduction is real, but it lowers carbamazepine's own level, which would not make quetiapine fail.
Carbamazepine strongly induces CYP3A4, which clears almost all quetiapine, so quetiapine levels fall severalfold and psychosis returns.
Carbamazepine does not inhibit CYP2D6, and higher quetiapine levels would cause sedation, not relapse.
Quetiapine is cleared by hepatic metabolism, not renal tubular secretion.
A 78-year-old long-term care resident taking benztropine becomes acutely confused, disoriented, and inattentive, with symptoms fluctuating through the day. Which intervention is most appropriate?
Benzodiazepines worsen delirium and falls in older adults unless the delirium is from alcohol or sedative withdrawal.
Acute, fluctuating inattention is delirium, and benztropine's anticholinergic load is the likely trigger, so removing it comes first.
An antipsychotic leaves the cause in place and is reserved for dangerous agitation in delirium.
Donepezil treats dementia and does not reverse a drug-induced delirium; adding it alongside an anticholinergic also works at cross purposes.
No. Know the strong inhibitors and inducers that recur in psychiatric prescribing, such as bupropion, fluoxetine and paroxetine for CYP2D6 and fluvoxamine for CYP1A2, and which drugs they affect.
How much neuroanatomy is tested?
The outline names it without a separate weight. Expect it tied to a symptom or a drug effect, such as which circuit a side effect comes from, rather than a labeling exercise.