PEBC MCQ study guide: Central Nervous System & Psychiatric Disorders

Providing Care – Clinical Care

Depression, anxiety, insomnia, epilepsy, and psychotic disorders.

Major Depressive Disorder

CANMAT (Canadian Network for Mood and Anxiety Treatments) 2023 guidelines list SSRIs as first-line pharmacotherapy for most patients, given comparable efficacy across agents but favourable tolerability versus older classes. SNRIs (venlafaxine, duloxetine), mirtazapine, and bupropion are also first-line options, selected by side-effect profile and patient-specific factors (e.g., bupropion avoids sexual dysfunction and is favoured with comorbid fatigue; mirtazapine helps with insomnia/appetite loss; bupropion is avoided in seizure disorder/eating disorder history).

Full antidepressant effect takes 4–6 weeks; an adequate trial before switching is generally 4–8 weeks at an adequate dose. Abrupt discontinuation of SSRIs/SNRIs (especially paroxetine, venlafaxine — short half-life) risks discontinuation syndrome (dizziness, "brain zaps," flu-like symptoms) — taper rather than stop abruptly.

Key interaction/safety points: SSRIs + triptans, tramadol, or other serotonergic agents → serotonin syndrome risk; SSRIs (especially fluoxetine, paroxetine) are potent CYP2D6 inhibitors; MAOIs require a strict washout (generally 2 weeks, 5 weeks for fluoxetine given its long half-life) before starting/stopping other serotonergic drugs.

Anxiety Disorders

SSRIs/SNRIs are first-line for generalized anxiety disorder, panic disorder, and social anxiety disorder — same agents as depression, though often started at lower doses with slower titration (anxious patients are more sensitive to early activating side effects).

Benzodiazepines provide rapid symptom relief but are recommended only for short-term/as-needed use due to tolerance, dependence, and withdrawal risk — not first-line for chronic maintenance therapy. Buspirone is a non-habit-forming alternative but has a slower onset and more modest efficacy.

Insomnia

Cognitive behavioural therapy for insomnia (CBT-I) is first-line over pharmacotherapy per most Canadian guidance. When medication is used short-term, options include the Z-drugs (zopiclone, zolpidem) or low-dose trazodone/mirtazapine off-label; benzodiazepines are an option but carry the same dependence concerns as in anxiety. All sedative-hypnotics carry fall risk in the elderly and are flagged on the Beers Criteria.

Epilepsy — Core Concepts

Drug selection depends on seizure type: broad-spectrum agents (valproic acid, lamotrigine, levetiracetam) cover both focal and generalized seizures; carbamazepine and phenytoin are effective for focal seizures but can worsen certain generalized seizure types (absence, myoclonic).

Valproic acid is teratogenic (neural tube defects) and generally avoided in women of childbearing potential when alternatives exist; lamotrigine and levetiracetam are relatively preferred in pregnancy. Enzyme-inducing anticonvulsants (carbamazepine, phenytoin, phenobarbital) reduce the efficacy of hormonal contraceptives and many other drugs via CYP induction — a critical counseling point.

Psychotic Disorders

Second-generation ("atypical") antipsychotics (risperidone, olanzapine, quetiapine, aripiprazole) are generally first-line over first-generation agents, offering lower extrapyramidal symptom (EPS) risk at the cost of greater metabolic side effects (weight gain, dyslipidemia, new-onset diabetes — especially olanzapine and clozapine).

Clozapine is reserved for treatment-resistant schizophrenia due to agranulocytosis risk, requiring mandatory regular absolute neutrophil count monitoring. All antipsychotics carry a boxed warning for increased mortality in elderly patients with dementia-related psychosis and are used with caution in that population.

High-yield points

CANMAT 2023: SSRIs remain first-line for depression; full effect takes 4–6 weeks; taper, don't stop abruptly (especially paroxetine/venlafaxine).
Benzodiazepines: short-term/as-needed only for anxiety/insomnia — not first-line maintenance therapy.
Valproic acid = teratogenic; avoid in women of childbearing potential when alternatives exist.
Enzyme-inducing anticonvulsants (carbamazepine, phenytoin) reduce hormonal contraceptive efficacy.
Second-generation antipsychotics: lower EPS, higher metabolic risk; clozapine requires mandatory ANC monitoring.

Guideline references

CANMAT 2023 Depression Guidelines
Canadian Psychiatric Association Practice Guidelines
Canadian League Against Epilepsy