Behavioral Health

Antipsychotic side effects: EPS, NMS, metabolic syndrome

Clinical Overview and When to Suspect Antipsychotic Side Effects

— First-generation antipsychotics (FGAs) (haloperidol, fluphenazine, chlorpromazine) → high D2 blockade → highest EPS and NMS risk

— Second-generation antipsychotics (SGAs) (olanzapine, clozapine, quetiapine, risperidone, aripiprazole) → 5HT2A/D2 → lower EPS but higher metabolic burden, especially olanzapine and clozapine

— Risperidone at doses >6 mg/day behaves like an FGA for EPS

— New psychiatric patient with muscle stiffness, tremor, restlessness, or abnormal movements after starting/uptitrating an antipsychotic

— Fever + rigidity + altered mental status + autonomic instability in any patient on a dopamine antagonist (including metoclopramide, prochlorperazine, promethazine) → assume NMS until proven otherwise

— Weight gain >5%, new dyslipidemia, A1c rising, or new HTN within 3–12 months of SGA initiation

Board pearl: Step 3 commonly hides EPS/NMS in non-psych stems — the post-op patient on prochlorperazine for nausea, the gastroparesis patient on chronic metoclopramide, or the dementia patient on off-label haloperidol. Always scan the med list for any D2 antagonist before anchoring on a primary neurologic diagnosis.

Step 3 management priority: Stop the offending agent first, then differentiate timeline (hours vs days vs weeks vs months) to identify which syndrome you're treating.

Antipsychotic adverse effects cluster into three exam-critical syndromes: extrapyramidal symptoms (EPS), neuroleptic malignant syndrome (NMS), and metabolic syndrome. All three appear on Step 3 because they drive outpatient monitoring, emergency triage, and medication reconciliation decisions.

When to suspect on the wards or in clinic:

Risk factors: young males (acute dystonia), elderly women (tardive dyskinesia), dehydration, agitation, IM depot use, and abrupt dose escalation (NMS)

Presentation Patterns and Key History

— Acute dystonia (hours to 4 days): sustained muscle contraction → torticollis, oculogyric crisis, laryngospasm, opisthotonos. Young men on high-potency FGAs are classic. Painful and frightening; laryngeal involvement is a medical emergency.

— Akathisia (days to weeks): subjective inner restlessness + objective inability to sit still, pacing, leg crossing/uncrossing. Frequently misdiagnosed as worsening psychosis or anxiety — a critical Step 3 trap because clinicians wrongly increase the antipsychotic.

— Parkinsonism (weeks): bradykinesia, cogwheel rigidity, resting tremor, masked facies, shuffling gait. Symmetric, unlike idiopathic PD.

— Tardive dyskinesia (months to years): choreoathetoid movements of face, tongue, lips (lip-smacking, tongue protrusion), trunk, limbs. Often irreversible.

— Onset over 1–3 days, often after dose increase, depot injection, dehydration, or addition of a second D2 blocker

— Tetrad: hyperthermia, "lead-pipe" rigidity, autonomic instability, altered mental status

— Patients on clozapine withdrawal or dopaminergic withdrawal (Parkinson's patients stopping levodopa) can develop a similar picture

— Weight gain trajectory, waist circumference change, family hx of DM/CVD

— Diet/activity baseline before initiation

— Look for olanzapine, clozapine, quetiapine (highest risk); aripiprazole, ziprasidone, lurasidone are weight-neutral

Key distinction: Akathisia vs psychotic agitation — akathisia is motor restlessness without internal psychotic content; the patient typically describes the discomfort and wants relief. Increasing the antipsychotic worsens it; this is the single highest-yield EPS pitfall on Step 3.

Board pearl: Always ask about anticholinergics, antiemetics, and recent depot injections — non-psychiatric exposures account for a surprising fraction of EPS/NMS stems.

EPS subtypes follow a predictable timeline — memorize the "hours-days-weeks-months" sequence:

NMS history clues:

Metabolic syndrome history:

Physical Exam Findings and Hemodynamic Assessment

— Fixed abnormal posture: head deviated (torticollis), eyes rolled up (oculogyric crisis), jaw clenched (trismus), back arched (opisthotonos)

— Stridor or voice change = laryngeal dystonia → airway emergency

— Normal mental status, normal vitals (distinguishes from NMS)

— Constant repositioning, marching in place, rocking, foot tapping

— Barnes Akathisia Rating Scale used clinically; not required on exam

— Symmetric bradykinesia and rigidity (vs asymmetric in idiopathic PD)

— Cogwheel rigidity, decreased arm swing, hypomimia

— Tremor often postural or perioral ("rabbit syndrome") rather than classic 4–6 Hz rest tremor

— Inspect face, mouth, tongue (protrusion, lateral movements, "fly-catcher" tongue), trunk, extremities

— Ask patient to open mouth, protrude tongue, tap fingers — provocative maneuvers unmask movements

— Hyperthermia >38°C, often >40°C

— Generalized "lead-pipe" rigidity (no cogwheeling — uniform resistance)

— Autonomic instability: labile BP, tachycardia, diaphoresis, tachypnea

— Altered mental status: stupor, mutism, catatonia

— Hyporeflexia or normal reflexes (contrast with serotonin syndrome's hyperreflexia/clonus)

— Waist circumference (>40 in men, >35 in women), BMI, BP, acanthosis nigricans

Key distinction: NMS rigidity is "lead-pipe" (uniform); serotonin syndrome features clonus, hyperreflexia, and tremor with lower extremity predominance. This single physical exam differentiator drives the entire workup pathway.

CCS pearl: On the CCS case, document continuous cardiac monitoring, core temperature, and neuro checks q1h for any suspected NMS — these orders are scored.

Acute dystonia exam:

Akathisia exam:

Drug-induced parkinsonism exam:

Tardive dyskinesia exam — AIMS exam:

NMS exam — the high-stakes one:

Metabolic exam:

Diagnostic Workup — Initial Labs

— CK — markedly elevated, often >1000 and frequently >10,000 U/L (rhabdomyolysis)

— CBC — leukocytosis 10–40k with left shift is typical

— BMP — AKI from rhabdo, hyperkalemia, metabolic acidosis

— LFTs — transaminitis common

— Coags — DIC can complicate severe cases

— UA + urine myoglobin — pigmented heme-positive urine without RBCs = myoglobinuria

— Iron studies — low serum iron is associated with NMS (board factoid)

— Blood/urine cultures, CXR, LP if indicated — rule out sepsis and meningitis, which mimic NMS

— CT head before LP if altered mental status

— ECG — QT prolongation from antipsychotic, arrhythmia risk from electrolyte derangements

— Baseline: weight/BMI, waist circumference, BP, fasting glucose or A1c, fasting lipid panel, personal/family hx

— 4 weeks, 8 weeks, 12 weeks: weight

— 12 weeks: fasting glucose, lipids, BP

— Annually thereafter: glucose/A1c, lipids, BP, weight

— Every 5 years: lipids (or sooner if abnormal)

Step 3 management: For NMS, CK trend guides resolution — CK normalization correlates with clinical recovery. Aggressive IV crystalloid (target UO >1–2 mL/kg/hr) prevents AKI from myoglobinuria.

Board pearl: A psychiatry patient with new fever and CK >1000 on an antipsychotic = NMS until proven otherwise. Do not anchor on "viral syndrome."

Acute dystonia / akathisia / drug-induced parkinsonism: Largely clinical diagnoses — no labs required to confirm. Check basic chemistry if dehydration suspected.

NMS workup (urgent, parallel with treatment):

Metabolic syndrome screening (ADA/APA consensus monitoring schedule):

Diagnostic Workup — Advanced or Confirmatory Studies

— LP with CSF analysis — typically normal in NMS; rules out meningitis/encephalitis

— CT/MRI brain — exclude structural lesions, anti-NMDA receptor encephalitis (especially in young women with psychosis + autonomic instability + dyskinesias)

— EEG — diffuse slowing in NMS; rules out nonconvulsive status epilepticus

— TSH — exclude thyroid storm

— Toxicology screen — exclude sympathomimetic toxicity (cocaine, amphetamines, MDMA), serotonin syndrome, anticholinergic toxidrome, malignant hyperthermia (anesthetic history)

— AIMS (Abnormal Involuntary Movement Scale) every 6 months on FGA, every 12 months on SGA (or every 3 and 6 months in high-risk patients)

— Rule out Huntington's disease (family hx, cognitive decline) and Wilson's disease (young patient, Kayser-Fleischer rings, low ceruloplasmin) when chorea is the presentation

— DaT-SPECT can distinguish from idiopathic PD when diagnosis unclear — drug-induced shows normal striatal uptake

Key distinction: NMS vs serotonin syndrome vs malignant hyperthermia vs anticholinergic toxidrome — all present with hyperthermia + AMS:

— NMS: rigidity, normal/hyporeflexia, days onset, D2 antagonist exposure

— Serotonin syndrome: hyperreflexia, clonus, hours onset, serotonergic exposure

— Malignant hyperthermia: minutes, succinylcholine/volatile anesthetic

— Anticholinergic: dry, flushed, mydriasis, no rigidity

Board pearl: Iron supplementation has been studied as adjunct in NMS given the low-iron association; not standard of care, but a board factoid.

NMS is a clinical diagnosis — DSM-5/Levenson criteria require recent dopamine antagonist exposure + hyperthermia + rigidity + ≥2 of (diaphoresis, dysphagia, tremor, incontinence, altered consciousness, mutism, tachycardia, labile BP, leukocytosis, elevated CK). No imaging confirms it.

Advanced workup is mostly to rule out mimics:

Tardive dyskinesia confirmatory tools:

Drug-induced parkinsonism:

Risk Stratification and First-Line Management Logic

— Mild (T <38, mild rigidity): Stop drug, supportive care, oral benzodiazepines, monitor on telemetry floor

— Moderate (T 38–40, marked rigidity, CK 1000–10,000): ICU, IV fluids, IV benzodiazepines, consider bromocriptine PO/NG or amantadine

— Severe (T >40, severe rigidity, CK >10,000, AKI, DIC): ICU, dantrolene IV, bromocriptine, intubation often required, consider ECT if refractory after 1 week

— Use ASCVD risk calculator for 10-year CV risk

— A1c ≥6.5% or fasting glucose ≥126 → diabetes per ADA

— Switch from olanzapine/clozapine to aripiprazole, ziprasidone, or lurasidone when feasible; clozapine cannot be switched in treatment-resistant schizophrenia — must add metformin instead

Step 3 management: For TD, first-line is a VMAT2 inhibitor (valbenazine or deutetrabenazine) — FDA-approved with strong evidence. Tetrabenazine is older, with more depression/parkinsonism side effects. Stop anticholinergics in TD (they worsen it) — opposite of acute EPS management.

Board pearl: The classic Step 3 trap: a schizophrenic with TD whose clinician adds benztropine — this worsens TD. Anticholinergics help acute EPS but harm TD.

Acute dystonia: Medical urgency, especially if laryngeal → secure airway if compromised, then IM/IV anticholinergic.

Akathisia: Outpatient management; reduce antipsychotic dose if possible, switch to lower-EPS agent (e.g., aripiprazole, quetiapine), add propranolol.

Drug-induced parkinsonism: Reduce dose or switch to SGA with lower D2 affinity; anticholinergic if young and not at risk for cognitive impairment.

Tardive dyskinesia: Cannot simply stop the antipsychotic in a stable psychotic patient — withdrawal worsens TD short-term. Switch to clozapine (lowest TD risk) or add VMAT2 inhibitor.

NMS — emergency stratification:

Metabolic syndrome risk stratification:

Pharmacotherapy — First-Line Drug Regimen

— IM/IV benztropine 1–2 mg or IM/IV diphenhydramine 25–50 mg — onset within 15–30 min

— Continue oral anticholinergic for 1–2 weeks to prevent recurrence

— Switch to lower-potency or SGA antipsychotic

— Propranolol 10–20 mg TID (titrate to 30–80 mg/day) — best evidence

— Benztropine 1–2 mg BID if coexisting parkinsonism

— Benzodiazepines (lorazepam, clonazepam) — second-line, short-term

— Mirtazapine 15 mg qhs — emerging evidence, useful in elderly who can't tolerate propranolol

— Benztropine 0.5–2 mg BID or trihexyphenidyl 2–5 mg TID — avoid in elderly (delirium, falls, urinary retention, cognitive impairment)

— Amantadine 100 mg BID — preferred in elderly

— Switch to quetiapine, clozapine, or aripiprazole if dose reduction insufficient

— Valbenazine 40 mg daily, titrate to 80 mg (VMAT2 inhibitor)

— Deutetrabenazine 6 mg BID, titrate up (VMAT2 inhibitor)

— Discontinue anticholinergics — they worsen TD

— Switch antipsychotic to clozapine in refractory cases

— Stop antipsychotic immediately

— IV benzodiazepines (lorazepam 1–2 mg IV q4–6h) — first-line for agitation, rigidity

— Bromocriptine 2.5 mg PO/NG q8h, titrate to 10 mg q8h — restores dopamine tone

— Dantrolene 1–2.5 mg/kg IV q6h for severe rigidity/hyperthermia (max 10 mg/kg/day)

— Amantadine 100 mg PO/NG BID-TID as alternative

— Continue dopaminergic agents 10 days after symptom resolution, then taper

— Metformin 500 mg BID, titrate to 1000 mg BID — best evidence for antipsychotic-induced weight gain, especially with clozapine/olanzapine

— GLP-1 agonists (semaglutide, liraglutide) — emerging strong evidence

— Statin per ASCVD risk

— Antihypertensives per JNC-8/ACC-AHA targets

Board pearl: Reintroducing the antipsychotic after NMS — wait at least 2 weeks after resolution, choose a lower-potency SGA (quetiapine), start low, titrate slowly. Recurrence risk ~30%.

Acute dystonia:

Akathisia (first-line is dose reduction + agent switch):

Drug-induced parkinsonism:

Tardive dyskinesia:

NMS pharmacotherapy:

Metabolic syndrome:

Procedural and Advanced Pharmacology Management

— Electroconvulsive therapy (ECT) — indicated when NMS fails to respond to bromocriptine/dantrolene after 5–7 days, or when underlying lethal catatonia is the diagnosis. Typically 6–10 sessions. Also valuable for the underlying psychotic illness once stabilized.

— Intubation/mechanical ventilation for respiratory failure from chest wall rigidity or aspiration

— Continuous renal replacement therapy (CRRT) for refractory hyperkalemia, severe AKI from rhabdo, or volume overload

— Active cooling (cooling blankets, cold IV fluids, ice packs to groin/axillae) for T >40°C; avoid antipyretics — ineffective because NMS hyperthermia is peripheral muscle-driven, not hypothalamic

— Clozapine is uniquely effective for treatment-resistant schizophrenia and reduces suicidality — often cannot be switched even with metabolic burden

— Requires REMS enrollment with weekly ANC monitoring × 6 months, then biweekly × 6 months, then monthly

— Hold if ANC <1000; discontinue permanently if ANC <500 (agranulocytosis)

— Monitor for myocarditis in first 4–8 weeks (troponin, ECG, CRP at baseline and weeks 1–4)

— Seizure risk dose-dependent — consider valproate prophylaxis at doses >600 mg/day

— Aripiprazole LAI, paliperidone LAI, risperidone LAI for adherence

— Caveat for NMS: depot agents persist for weeks — recovery is prolonged after NMS from LAIs

— Deep brain stimulation (GPi) for severe refractory TD

— Botulinum toxin for focal tardive dystonia

CCS pearl: In a CCS NMS case, order dantrolene, bromocriptine, IV fluids, cooling blanket, continuous monitoring, foley with strict I/O, ICU transfer — these are scored interventions. Don't forget to D/C the antipsychotic as your first order.

Board pearl: Clozapine titration that's interrupted >48 hours must restart at 12.5 mg — sudden retitration can cause orthostasis, sedation, and NMS-like reactions. This is a frequent transition-of-care board question.

Severe refractory NMS:

Clozapine-specific considerations:

Long-acting injectable (LAI) antipsychotics:

Tardive dyskinesia advanced options:

Special Populations — Elderly and Renal/Hepatic Impairment

— FDA black box warning: antipsychotics increase mortality in dementia-related psychosis (CV events, infection) — only use when behavioral interventions fail and risk of harm is significant

— Avoid anticholinergics (benztropine, trihexyphenidyl, diphenhydramine) per Beers Criteria — delirium, falls, urinary retention, constipation, glaucoma

— Prefer amantadine for drug-induced parkinsonism in elderly (but reduce dose in CKD)

— Higher risk of orthostatic hypotension with quetiapine, clozapine, olanzapine → fall risk

— Higher risk of TD (especially elderly women)

— Start half the usual dose and titrate slowly

— Paliperidone is largely renally excreted — avoid or dose-reduce if CrCl <50

— Amantadine requires dose adjustment: CrCl 30–50 → 100 mg daily; <30 → 100 mg every 2–3 days

— Lithium (often co-prescribed) — contraindicated in advanced CKD; narrow therapeutic window

— Valbenazine — no adjustment for mild–moderate CKD; avoid severe

— Most antipsychotics are hepatically metabolized (CYP3A4, CYP2D6) — olanzapine, quetiapine, risperidone all require caution

— Paliperidone preferred in hepatic impairment (not hepatically metabolized)

— Avoid chlorpromazine (cholestatic jaundice risk)

— Valbenazine contraindicated in moderate–severe hepatic impairment

— Higher mortality, more likely to be misdiagnosed as sepsis or delirium

— Lower fever thresholds — even T 37.8 with rigidity warrants concern

Step 3 management: For a 70-year-old with Lewy body dementia and visual hallucinations, avoid all FGAs and risperidone/olanzapine (severe sensitivity reactions, parkinsonism worsening). Use quetiapine at low dose (12.5–25 mg) or pimavanserin (FDA-approved for Parkinson's disease psychosis — no D2 activity).

Board pearl: Lewy body dementia + antipsychotic = NMS-like reaction in up to 50%. Pimavanserin or low-dose quetiapine only.

Elderly considerations:

Renal impairment:

Hepatic impairment:

NMS in elderly:

Special Populations — Pregnancy, Pediatrics, and Other Subgroups

— Untreated psychosis carries significant risk to mother and fetus — do not reflexively stop antipsychotics

— Preferred agents: haloperidol (most pregnancy data), olanzapine, quetiapine, risperidone all category C with reassuring registry data

— Avoid clozapine if possible (neonatal agranulocytosis, floppy baby) but not absolutely contraindicated

— Third-trimester exposure → neonatal extrapyramidal symptoms and withdrawal (irritability, feeding issues, respiratory distress) — typically self-limited

— Gestational diabetes risk with olanzapine/clozapine — screen earlier (24 weeks or sooner)

— Olanzapine, quetiapine, risperidone considered relatively safe

— Avoid clozapine (concentrates in milk, agranulocytosis risk)

— SGAs FDA-approved for schizophrenia (≥13), bipolar (≥10), autism-associated irritability (≥5 for risperidone/aripiprazole), Tourette's

— Higher metabolic risk than adults — aggressive weight monitoring (BMI percentile every visit), lipids, glucose

— Aripiprazole preferred for Tourette's and autism irritability (lowest metabolic burden)

— Risperidone causes more hyperprolactinemia → gynecomastia, galactorrhea, amenorrhea, growth/puberty effects

— Adolescents gain 2–3× more weight than adults on the same antipsychotic

— Metformin should be considered earlier

— CYP3A4 interactions with protease inhibitors → reduce antipsychotic dose

— Quetiapine levels can rise 5–10× with ritonavir

Key distinction: Risperidone vs aripiprazole for prolactin — risperidone potently raises prolactin (full D2 antagonist); aripiprazole lowers prolactin (partial agonist). This drives the Step 3 question about an adolescent with galactorrhea on an SGA.

Board pearl: Pregnant women with schizophrenia who discontinue antipsychotics have ~65% relapse rate by delivery — counseling about risk-benefit is a Step 3 ethics/safety theme.

Pregnancy:

Breastfeeding:

Pediatrics:

Adolescents and weight:

Patients with HIV on ART:

Complications and Adverse Outcomes

— Rhabdomyolysis → AKI (most common cause of death)

— Aspiration pneumonia from dysphagia/altered mental status

— DIC, PE, MI from hypercoagulable state and immobility

— Respiratory failure from chest wall rigidity

— Mortality 10–20% untreated; <5% with prompt recognition

— Recurrence rate ~30% with rechallenge

— Laryngeal dystonia → airway obstruction, death

— Falls and fractures from parkinsonism/orthostasis

— Aspiration from oropharyngeal dyskinesia in TD

— Functional and social disability from visible TD movements — stigma, employment impact

— Tardive dystonia — fixed painful postures, often permanent

— Schizophrenic patients die 15–20 years earlier than the general population, largely from cardiovascular disease

— Type 2 DM incidence 2–3× general population

— MI, stroke, sudden cardiac death — antipsychotics also prolong QT (especially ziprasidone, IV haloperidol, thioridazine)

— Hyperprolactinemia → osteoporosis, sexual dysfunction, infertility

— Agranulocytosis (clozapine) — fatal infections

— Myocarditis (clozapine) — first 4–8 weeks

— Seizures (clozapine, chlorpromazine — dose-dependent)

— Anticholinergic effects (low-potency FGAs, olanzapine, clozapine) — constipation (clozapine ileus can be fatal), urinary retention, blurred vision

— Cataracts (quetiapine — slit-lamp exam recommended)

— VTE — antipsychotics independently increase risk

— Stroke and death in elderly with dementia — black box

Step 3 management: A clozapine patient presenting with abdominal pain and no bowel movement = clozapine-induced ileus — potentially fatal. Aggressive bowel regimen at initiation, low threshold for imaging.

Board pearl: QT prolongation — get baseline ECG before starting ziprasidone, IV haloperidol, thioridazine, pimozide, especially with electrolyte abnormalities or other QT-prolonging drugs.

NMS complications:

EPS complications:

Metabolic complications:

Other antipsychotic adverse effects:

When to Escalate Care — ICU, Consult, or Inpatient Triage

— Laryngeal dystonia with stridor → ED, IM benztropine/diphenhydramine, airway team

— Suspected NMS → ED, then ICU

— Severe akathisia with suicidality — akathisia is a documented suicide risk factor → ED evaluation

— T >40°C

— CK >5000 or rising rapidly

— AKI (Cr >1.5× baseline)

— Hemodynamic instability requiring pressors

— Respiratory compromise / need for intubation

— Altered mental status with airway protection concerns

— DIC or other end-organ dysfunction

— Any suspected NMS — co-management with medicine/ICU

— New TD diagnosis — need for antipsychotic switch decisions

— Pregnancy with active psychosis

— Treatment-resistant psychosis — clozapine candidacy

— Acute behavioral emergency in patient on multiple antipsychotics

— Atypical movement disorder — to rule out HD, Wilson's, PD

— Refractory dystonia requiring botulinum toxin

— DBS evaluation for severe TD

— Decompensated psychosis with safety concerns

— Catatonia (which can be confused with NMS)

— Need for ECT

CCS pearl: On a CCS NMS case, transfer to ICU is a scored order. Don't forget to cancel scheduled antipsychotic doses in the orders, place DVT prophylaxis (high VTE risk from immobility + antipsychotic), and order q1h vitals with continuous telemetry.

Step 3 management: In a CCS akathisia-induced suicide attempt case, admission to an inpatient psychiatric unit with propranolol initiation and antipsychotic switch to aripiprazole or quetiapine is the correct path — not increasing the current antipsychotic.

Board pearl: A "calm" psychiatric patient on antipsychotics with mutism, immobility, waxy flexibility — distinguish catatonia (responds to lorazepam challenge) from NMS (rigidity, fever, autonomic). Both can coexist.

Emergency department / immediate management:

ICU admission criteria for NMS:

Psychiatric consultation indications:

Neurology consultation:

Inpatient psychiatric admission:

Key Differentials — Same-Category Movement and Drug-Related Causes

— Alcohol/benzodiazepine withdrawal — tremor, hyperthermia, autonomic instability, seizures

— Dopaminergic withdrawal in Parkinson's patients stopping levodopa abruptly → parkinsonism-hyperpyrexia syndrome (NMS-like)

— Idiopathic Parkinson's disease — asymmetric onset, 4–6 Hz resting tremor, normal DaT-SPECT in drug-induced

— Other dopamine antagonists: metoclopramide, prochlorperazine, promethazine (commonly missed)

— Calcium channel blocker (flunarizine, cinnarizine) — not US, but on transferred patients

— Valproate — postural tremor and parkinsonism

— Conversion disorder

— Seizure with focal posturing

— Tetanus — risus sardonicus, trismus, generalized rigidity, wound history

— Strychnine poisoning — generalized muscle spasms with preserved consciousness

— Huntington's disease, Wilson's disease, Sydenham chorea, levodopa-induced dyskinesia in PD

Key distinction: Lorazepam challenge (1–2 mg IV) — rapid improvement suggests catatonia; minimal change with persistent rigidity/fever suggests NMS. Both can coexist (catatonia can evolve into NMS).

Board pearl: A patient on chronic metoclopramide for gastroparesis with new tongue movements = tardive dyskinesia — black box warning on metoclopramide. Limit duration to <12 weeks.

Serotonin syndrome — hyperreflexia, clonus (especially lower extremities), tremor, diarrhea, hours-to-days onset; serotonergic agent exposure (SSRIs, SNRIs, MAOIs, tramadol, linezolid, ondansetron, triptans, dextromethorphan)

Malignant hyperthermia — within minutes of volatile anesthetic or succinylcholine; treat with dantrolene; RYR1 mutation

Anticholinergic toxidrome — "hot, dry, red, blind, mad, and bloated" — hyperthermia, mydriasis, dry skin/mucous membranes, urinary retention, no rigidity; physostigmine is antidote

Sympathomimetic toxicity (cocaine, amphetamines, MDMA, bath salts) — hyperthermia, mydriasis, diaphoresis, hypertension, agitation; benzodiazepines first-line

Withdrawal syndromes:

Drug-induced parkinsonism mimics:

Acute dystonia mimics:

Tardive dyskinesia mimics:

Key Differentials — Other-Category Causes

— Meningitis/encephalitis — meningismus, photophobia, CSF pleocytosis; HSV encephalitis in temporal lobes on MRI

— Sepsis — source-driven, less rigidity, more hypotension than NMS

— Brain abscess — focal neurologic findings, ring-enhancing lesion

— Thyroid storm — hyperthermia, tachycardia, AMS, no rigidity; precipitated by stress/infection; treat with PTU/methimazole, beta-blocker, steroids, iodine

— Adrenal crisis — hypotension, hyperkalemia, hyponatremia

— Pheochromocytoma — paroxysmal HTN, headache, diaphoresis

— Anti-NMDA receptor encephalitis — young women, psychosis + seizures + dyskinesias + autonomic instability; ovarian teratoma in 50%; CSF anti-NMDA antibodies; treat with steroids, IVIG, plasmapheresis, tumor removal

— Often misdiagnosed as primary psychosis with "NMS"

— Nonconvulsive status epilepticus — confusion, automatisms; EEG diagnosis

— Catatonia (idiopathic or secondary) — mutism, posturing, waxy flexibility; responds to lorazepam, then ECT

— Stroke — focal deficits, imaging-based

— Hypertensive encephalopathy / PRES — severe HTN, headache, vision changes

— Cushing's syndrome — central obesity, moon facies, striae, HTN, hyperglycemia, hypokalemia

— Hypothyroidism — weight gain, fatigue, dyslipidemia

— PCOS in women — independent contributor to metabolic syndrome and frequently coexists

— Lifestyle/dietary obesity — independent of antipsychotic

— Environmental exposure, hot/dry skin (classic) or sweating (exertional), hyperthermia, AMS; no rigidity initially

Key distinction: Anti-NMDA receptor encephalitis in a young woman with new psychosis getting worse on antipsychotics + autonomic instability — always image for ovarian teratoma before labeling as NMS.

Board pearl: A schizophrenic with weight gain — rule out hypothyroidism and Cushing's before attributing entirely to the antipsychotic.

Infectious causes of fever + AMS + autonomic changes:

Endocrine emergencies:

Autoimmune encephalitis:

Neurologic emergencies:

Metabolic syndrome differentials:

Heat stroke:

Secondary Prevention, Discharge Medications, and Long-Term Plan

— Wait ≥2 weeks after full resolution before rechallenge

— Choose lower-potency SGA (quetiapine, clozapine) at low dose with slow titration

— Document the NMS event clearly in chart and patient med list — recurrence risk ~30%

— Avoid dehydration triggers, depot injections initially

— Counsel patient/family to recognize early signs (fever, stiffness)

— Discharge medications: continue dopaminergic agent (bromocriptine/amantadine) 10 days past resolution, then taper

— Continue VMAT2 inhibitor indefinitely if benefit

— Switch to clozapine if psychosis controlled but TD progressing

— Avoid anticholinergics

— Periodic AIMS exam

— Lifestyle: Mediterranean or DASH diet, ≥150 min/week moderate aerobic activity, structured weight-loss program

— Pharmacologic:

— Metformin 500–1000 mg BID — first-line for antipsychotic weight gain or new prediabetes/DM

— GLP-1 agonist (semaglutide) — strong data, increasingly first-line for obesity

— Statin per ASCVD risk (≥7.5% 10-year risk or LDL ≥190 or DM ≥40 yo)

— Antihypertensives to <130/80 per ACC-AHA

— Aspirin only per current USPSTF (40–59 with high ASCVD risk, shared decision)

— Smoking cessation — schizophrenia patients smoke at 3× general rate; bupropion + nicotine replacement are safe; varenicline is also safe (FDA removed black box)

— Cross-titration over 2–4 weeks rather than abrupt switch

— Aripiprazole, ziprasidone, lurasidone are weight-neutral options

Step 3 management: A schizophrenic on clozapine with A1c 7.2% — do NOT stop clozapine. Add metformin, consider GLP-1, intensify lifestyle. Clozapine has unique antisuicidal benefit and is rarely switched.

Board pearl: Statin choice in schizophrenia — be aware of CYP3A4 interactions (avoid simvastatin/lovastatin with strong CYP3A4 inhibitors); rosuvastatin or pravastatin are safer choices.

Post-NMS discharge:

TD long-term plan:

Metabolic syndrome secondary prevention (multidimensional):

Antipsychotic switch decisions:

Follow-Up, Monitoring Parameters, and Counseling

— Baseline: personal/family hx (DM, dyslipidemia, CVD), weight/BMI, waist circumference, BP, fasting glucose or A1c, fasting lipid panel

— 4 weeks: weight

— 8 weeks: weight

— 12 weeks: weight, BP, fasting glucose, fasting lipids

— Quarterly: weight

— Annually: BP, fasting glucose/A1c

— Every 5 years: lipids (or sooner if abnormal)

— AIMS exam every 6 months on FGA, every 12 months on SGA (every 3 months for high-risk patients — elderly, women, mood disorder, diabetes, prior EPS)

— Document baseline AIMS before any antipsychotic initiation

— ANC weekly × 6 months, biweekly × 6 months, monthly thereafter (REMS-mandated)

— Troponin, CRP, ECG at baseline and weekly × 4 weeks for myocarditis screen

— Lipids, glucose, weight per ADA/APA + additional vigilance

— Lithium level every 6–12 months at steady state, more often with changes

— TSH, BUN/Cr annually

— Recognize early NMS signs — call 911 for fever + stiffness on antipsychotic

— Distinguish akathisia from anxiety — report restlessness rather than self-medicate

— Adherence — abrupt cessation triggers withdrawal dyskinesias and relapse

— Lifestyle counseling at every visit (motivational interviewing)

— Pregnancy planning — pre-conception medication review

— Avoid alcohol/cannabis interactions

— Hospital discharge med rec must explicitly list antipsychotic, dose, indication

— Communicate any EPS/NMS history to all subsequent providers

— Update problem list with "history of NMS" prominently

Step 3 management: A patient who misses 2 clozapine doses — restart at 12.5 mg and retitrate. Reinitiating at the prior dose risks cardiovascular collapse and seizures. This is a transition-of-care safety question.

Board pearl: Patients with schizophrenia have <50% adherence at 1 year; LAI antipsychotics are evidence-based to reduce hospitalization.

ADA/APA monitoring protocol for SGA — memorize the schedule:

EPS monitoring:

Clozapine monitoring:

Lithium-antipsychotic combinations:

Patient counseling priorities:

Care transitions:

Ethical, Legal, and Patient Safety Considerations

— Must discuss TD risk (irreversible), metabolic syndrome, NMS, sexual dysfunction, sedation, and mortality risk in elderly with dementia

— Document AIMS baseline and serial AIMS — failure to monitor is a malpractice flag

— In adolescents and elderly with dementia, document shared decision-making with family

— Patients with acute psychosis may lack decision-making capacity — assess understanding, appreciation, reasoning, expression of choice

— Most states permit emergency involuntary medication for imminent danger; non-emergency forced medication typically requires court order (varies by state)

— Right to refuse medication exists even in involuntary admissions in most jurisdictions

— Suspected child abuse, elder abuse, dependent adult abuse — mandatory

— Duty to warn / Tarasoff — when patient makes specific threat against identifiable victim

— Driving impairment — variable by state; counsel patient on sedation

— Increased mortality in dementia-related psychosis (all antipsychotics)

— Suicidality in young adults on antidepressants (often co-prescribed)

— Metoclopramide — TD risk, limit to 12 weeks

— Hospital discharge: med rec must specify whether antipsychotic was newly started (for delirium) and whether it should be discontinued — failure to stop a delirium-related antipsychotic at discharge contributes to long-term antipsychotic exposure in elders

— Clozapine transitions: ED providers must know REMS, ANC requirements

— Care coordination with PCP for metabolic monitoring — psychiatrists alone often miss this

— OBRA regulations — require documented indication, regular review, and dose-reduction attempts

— Inappropriate use for agitation in dementia without behavioral interventions first is a regulatory/legal risk

Step 3 patient safety pearl: The #1 transition-of-care safety event with antipsychotics is continuing a hospital-initiated antipsychotic indefinitely after discharge — particularly in elderly patients started on haloperidol/quetiapine for ICU delirium. Always specify a stop date or taper plan in the discharge summary.

Board pearl: Beers Criteria flags antipsychotics in elderly — use only when alternatives have failed and document rationale.

Informed consent for antipsychotics:

Capacity and involuntary treatment:

Mandatory reporting:

Black box warnings — document discussion:

Transition-of-care patient safety:

Antipsychotics in nursing homes:

High-Yield Associations and Rapid-Fire Clinical Facts

Board pearl: The fastest mnemonic — "NMS = Nasty Muscle Stiffness" (rigidity), SS = Serotonin Spasms (clonus, hyperreflexia). The reflex exam alone separates the two ~90% of the time.

Highest EPS risk: haloperidol, fluphenazine; risperidone at high dose

Lowest EPS risk: clozapine, quetiapine

Highest metabolic risk: clozapine, olanzapine

Lowest metabolic risk: aripiprazole, ziprasidone, lurasidone

Highest QT prolongation: thioridazine, ziprasidone, IV haloperidol, pimozide

Highest prolactin elevation: risperidone, paliperidone, haloperidol

Lowest prolactin: aripiprazole (partial agonist — can lower prolactin)

Highest anticholinergic burden: clozapine, chlorpromazine, olanzapine

Highest seizure risk: clozapine (dose-dependent), chlorpromazine

Highest agranulocytosis risk: clozapine

Best evidence for treatment-resistant schizophrenia: clozapine

Best evidence for reducing suicidality in schizophrenia: clozapine

First-line for acute dystonia: IM benztropine or diphenhydramine

First-line for akathisia: propranolol (or dose reduction/switch)

First-line for drug-induced parkinsonism in young: benztropine; in elderly: amantadine

First-line for TD: VMAT2 inhibitor (valbenazine, deutetrabenazine); switch to clozapine if refractory

First-line for NMS: stop drug, supportive care, IV benzodiazepines; dantrolene + bromocriptine for severe

First-line for antipsychotic-induced weight gain: metformin; GLP-1 emerging

NMS mortality: 10–20% untreated, <5% with prompt treatment

NMS recurrence on rechallenge: ~30%

Wait time before rechallenge after NMS: ≥2 weeks

Restart clozapine after >48h miss: at 12.5 mg

TD risk per year on FGA: ~5% per year; on SGA ~1% per year

TD risk factors: elderly, female, mood disorder, DM, prior EPS, longer duration

Pregnancy preferred: haloperidol, olanzapine, quetiapine (with metabolic monitoring)

Breastfeeding avoid: clozapine

Lewy body dementia: avoid antipsychotics; pimavanserin or low-dose quetiapine

Parkinson's psychosis: pimavanserin (no D2 activity)

Monitoring interval lipids: at 12 weeks, then every 5 years (or sooner if abnormal)

Iron in NMS: low serum iron association

Mortality gap in schizophrenia: 15–20 years, mostly cardiovascular

Board Question Stem Patterns

Board pearl: When the stem mentions dose escalation, dehydration, depot injection, or recent addition of a second D2 blocker → think NMS.

Pattern 1 — Acute dystonia: 22-year-old man started on haloperidol 3 days ago for new psychosis presents with neck twisted to one side and eyes rolled upward. → IM benztropine or diphenhydramine

Pattern 2 — Akathisia: Schizophrenic patient on risperidone for 2 weeks paces constantly, "feels like jumping out of skin," and clinician has been increasing the antipsychotic dose. → Akathisia, reduce dose / add propranolol / switch agent — NOT increase

Pattern 3 — NMS: Patient on haloperidol after dose increase presents with T 40°C, generalized "lead-pipe" rigidity, BP 180/110, HR 130, confused, CK 8,000. → Stop antipsychotic, IV fluids, ICU, dantrolene + bromocriptine

Pattern 4 — NMS vs serotonin syndrome: Patient on SSRI started on tramadol with hyperreflexia, clonus, agitation, T 38.5. → Serotonin syndrome — cyproheptadine, NOT dantrolene

Pattern 5 — TD: 60-year-old woman on FGA × 10 years with lip-smacking and tongue-protrusion movements. Clinician adds benztropine. → WRONG — anticholinergics worsen TD. Start valbenazine; consider clozapine switch

Pattern 6 — Metabolic monitoring: Patient started on olanzapine 12 weeks ago — what to check now? → Fasting glucose, lipids, BP, weight

Pattern 7 — Olanzapine weight gain: Schizophrenic gained 15 lb on olanzapine, A1c 6.4%. → Add metformin; consider switch to aripiprazole/ziprasidone if psychiatrically feasible

Pattern 8 — Hidden D2 antagonist: Post-op patient on prochlorperazine for nausea develops oculogyric crisis. → Acute dystonia from prochlorperazine — IM benztropine

Pattern 9 — Metoclopramide TD: Chronic gastroparesis patient on metoclopramide × 2 years with tongue dyskinesia. → TD from metoclopramide; stop drug

Pattern 10 — Lewy body sensitivity: Elderly patient with visual hallucinations + parkinsonism started on haloperidol → severe rigidity, hyperthermia. → Lewy body dementia with antipsychotic sensitivity — stop drug; use pimavanserin or low-dose quetiapine

Pattern 11 — Clozapine miss: Patient missed clozapine × 4 days, asks to restart full dose. → Restart at 12.5 mg and retitrate

Pattern 12 — NMS rechallenge: Patient recovered from NMS 3 weeks ago; needs antipsychotic for ongoing psychosis. → Low-potency SGA (quetiapine) at low dose, slow titration

One-Line Recap

Antipsychotic toxicity reduces to three patterns: EPS (timeline-driven: dystonia hours → akathisia days → parkinsonism weeks → TD months) treated with anticholinergics acutely but VMAT2 inhibitors chronically; NMS (fever + lead-pipe rigidity + autonomic + AMS + ↑CK) treated by stopping the drug, supportive care, and dantrolene/bromocriptine in severe cases; and metabolic syndrome managed by ADA/APA monitoring schedule, switching to weight-neutral SGAs, and metformin or GLP-1 agonists.

Board pearl: The single most important Step 3 cognitive habit with antipsychotics is to scan every medication list for D2 antagonists (haloperidol, risperidone, olanzapine, quetiapine, metoclopramide, prochlorperazine, promethazine) when evaluating fever, rigidity, movement disorders, or new metabolic derangements — non-psychiatric stems are where these diagnoses are most often missed.

EPS rule of thumb: Anticholinergics rescue acute EPS but worsen tardive dyskinesia — opposite directions for opposite syndromes.

NMS rule of thumb: Lead-pipe rigidity + fever + ↑CK on a D2 blocker (including antiemetics like metoclopramide and prochlorperazine) — stop drug first, then treat; mortality drops from 20% to <5% with recognition.

Metabolic rule of thumb: Check baseline, 12 weeks, then annually — olanzapine and clozapine are the worst offenders; metformin first-line for weight gain; clozapine is rarely switched even with metabolic burden because of its unique antisuicidal and treatment-resistance efficacy.

Akathisia rule of thumb: Inner restlessness in a psychiatric patient is not worsening psychosis — propranolol or dose reduction, never escalation.