Psychotropic drugs act on neurotransmitter systems. Knowing the system predicts both effect and adverse effects.

Most antidepressants and mood stabilizers need weeks for full effect; antipsychotics calm agitation within days but full antipsychotic effect takes weeks.

Before starting any psychotropic

• Target symptoms and baseline mental status; suicide risk
• Allergies, all medications and supplements (St. John's wort, tryptophan), alcohol and drug use
• Pregnancy status and plans, breastfeeding
• Cardiac history, seizure history, liver and kidney disease
• Weight, BMI, waist, blood pressure, pulse (lying and standing)

Monitor during treatment: response, adherence, adverse effects (below), suicidality in the first weeks and after dose changes, and falls in older adults.

Therapeutic levels

Antidepressants — onset 2–4 weeks, full effect 6–8 weeks.

• Boxed warning (all antidepressants): increased suicidal thoughts and behavior in children, adolescents, and young adults under 25. Monitor closely during the first months and after dose changes. The warning remains current.
• Discontinuation syndrome after abrupt stop (especially paroxetine, venlafaxine): dizziness, "electric shock" sensations, flu-like symptoms, irritability, insomnia — taper slowly.
• MAOI rules: avoid tyramine — aged cheeses, cured or fermented meats (salami), soy sauce and fermented soy, sauerkraut, tap and unpasteurized beer, spoiled or overripe foods; avoid decongestants, stimulants, meperidine, tramadol, dextromethorphan, other antidepressants, St. John's wort. Allow 14 days between an MAOI and other serotonergic antidepressants in either direction (5 weeks after stopping fluoxetine before starting an MAOI). Dietary restriction is not needed at the lowest selegiline patch dose.

Antipsychotics

• Boxed warning (all antipsychotics): increased mortality in older adults with dementia-related psychosis (mostly cardiovascular and infectious deaths). Not approved for this use; use nonpharmacologic approaches first (consistent with MS-066).
• Clozapine REMS change: the US Clozapine REMS was eliminated (effective June 13, 2025) — pharmacies no longer need to verify ANC results before dispensing. The boxed warning and the ANC monitoring schedule in the label remain; the label still recommends ANC monitoring.
• Clozapine ANC action thresholds (general population, current labeling): 1,000–1,499/µL (1.0–1.49 × 10⁹/L, mild) → continue, check ANC three times weekly; 500–999/µL (0.5–0.99 × 10⁹/L, moderate) → interrupt clozapine, notify prescriber, hematology consultation, resume only when ANC ≥ 1,000/µL; below 500/µL (below 0.5 × 10⁹/L, severe) → discontinue, hematology consultation. In benign ethnic neutropenia, 500–999/µL → continue with three-times-weekly ANC; below 500/µL → discontinue
• Long-acting injectables (e.g., paliperidone, aripiprazole, haloperidol decanoate) improve adherence; olanzapine pamoate requires 3-hour post-injection monitoring for delirium/sedation syndrome.

Extrapyramidal and movement effects

Anticholinergic agents (benztropine, trihexyphenidyl, diphenhydramine): dry mouth, constipation, urinary retention, blurred vision, confusion in older adults; avoid in narrow-angle glaucoma and prostatic hyperplasia.

Mood stabilizers

Anxiolytics and hypnotics

ADHD stimulants (methylphenidate, amphetamines): boxed warning for abuse, misuse, and addiction; insomnia, appetite loss, growth monitoring in children, increased heart rate and BP; give early in the day.

Listed in priority order.

1. Recognize emergencies — NMS, serotonin syndrome, lithium toxicity, hypertensive crisis, laryngeal dystonia, agranulocytosis (Section 7)
2. Suicide safety — monitor closely as energy returns in the first weeks of antidepressant treatment; limit supply for high-risk clients
3. Check levels and labs before giving — hold lithium and notify provider if the level is above range or toxicity signs appear; check ANC before clozapine doses and hold and notify the prescriber when ANC is below 1,000/µL (below 500/µL in benign ethnic neutropenia)
4. Monitor vital signs — orthostatic BP (rise slowly), temperature (fever may signal NMS, agranulocytosis, or myocarditis)
5. Screen for movement disorders (AIMS) and metabolic changes
6. Promote adherence — explain delayed onset; address adverse effects early; consider long-acting injectables
7. Manage adverse effects — sugar-free gum and sips of water for dry mouth; fiber, fluids, activity for constipation (report no bowel movement for several days on clozapine); sunscreen with low-potency antipsychotics

• Antidepressants take 2–4 weeks to start working — do not stop early; never stop abruptly
• Report worsening mood, agitation, or suicidal thoughts right away, especially under age 25
• Lithium: drink about 2–3 L of fluid daily, keep salt intake consistent, avoid NSAIDs unless approved, report vomiting, diarrhea, heavy sweating, or fever (dehydration raises levels); know toxicity signs; keep lab appointments
• MAOIs: carry a list of forbidden foods and drugs; seek emergency care for severe headache, stiff neck, palpitations
• Clozapine: keep all blood tests; report fever, sore throat, flu-like symptoms, chest pain, shortness of breath, or constipation immediately; tell the prescriber if you stop or start smoking
• Antipsychotics: rise slowly; watch weight and diet; avoid heat exhaustion
• Avoid alcohol with psychotropics; do not drive until sedation is known
• Discuss pregnancy plans before conceiving

Serotonin syndrome vs. neuroleptic malignant syndrome

Lithium toxicity

Action: hold lithium, notify provider, obtain level, IV isotonic saline as ordered; hemodialysis for severe toxicity. Activated charcoal does not bind lithium.

Other emergencies

• Hypertensive crisis (MAOI): severe occipital headache, stiff neck, palpitations, hypertension, sweating → emergency BP control
• Agranulocytosis (clozapine, carbamazepine): fever, sore throat → hold drug, check ANC/CBC
• Anticholinergic toxicity: hot, dry, flushed skin, dilated pupils, urinary retention, delirium
• TCA overdose: wide QRS, dysrhythmias, seizures → sodium bicarbonate per protocol

• Antidepressant boxed warning: suicidality under age 25 — monitor early treatment
• Antipsychotic boxed warning: increased death in older adults with dementia-related psychosis
• Clozapine: treatment-resistant schizophrenia; REMS eliminated in 2025, but ANC monitoring and the boxed warning remain; report fever or sore throat
• Lithium 0.6–1.2 mEq/L, trough 12 h post-dose; toxicity above 1.5; dehydration, low sodium, thiazides, NSAIDs, ACE inhibitors raise levels
• MAOI + tyramine = hypertensive crisis; 14-day washout
• Serotonin syndrome = rapid, clonus/hyperreflexia, diarrhea; NMS = slow, lead-pipe rigidity, very high fever, high CK
• Acute dystonia → IM/IV benztropine or diphenhydramine; TD → valbenazine/deutetrabenazine, not anticholinergics
• SSRI: nausea, sexual dysfunction, hyponatremia, bleeding; taper to avoid discontinuation syndrome
• TCAs: anticholinergic, orthostatic, lethal cardiotoxic overdose
• Valproate: hepatotoxicity, pancreatitis, neural tube defects, weight gain; avoid alcohol
• Benzodiazepines: dependence, taper; deadly with opioids; buspirone has no dependence and delayed onset