Step 2 CK · Psychiatry

Psychopharmacology & Emergencies

Name: Psychopharmacology & Emergencies
Creator: Veli Bakalov, MD

The psychiatric emergencies where the right antidote is the difference

Psychiatry·Assessment, Emergencies & Geriatric Psychiatry·4 min read·9 high-yield points·Reviewed by Veli Bakalov, MD @HemeOncBuddy

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Serotonin syndrome: serotonergic combinations (SSRI plus MAOI, tramadol, linezolid, triptans, dextromethorphan) → within 24 h clonus, hyperreflexia (legs > arms), mydriasis, diaphoresis → stop the drugs, give cyproheptadine.
NMS: dopamine antagonist (or abrupt dopamine-agonist withdrawal) → over days fever, lead-pipe rigidity, hyporeflexia, autonomic instability, very high CK → stop the drug, cool, dantrolene or bromocriptine.
Anticholinergic toxicity is DRY: hot, flushed, mydriatic, delirious, with urinary retention and ileus; sweating argues against it; physostigmine if severe.
Lithium toxicity >1.5 mEq/L (coarse tremor, ataxia → confusion, seizures, arrhythmia) is precipitated by dehydration, NSAIDs, thiazides, ACE inhibitors, or renal failure; IV fluids, hemodialysis if >4 mEq/L with impaired kidney function, >5 mEq/L, or decreased consciousness, seizures, or dysrhythmias.
Antidepressant discontinuation (FINISH) is worst with paroxetine and venlafaxine and least with fluoxetine; prevent it by tapering.
Agitation: de-escalate first, then haloperidol ± lorazepam; benzodiazepines are often preferred for stimulant or anticholinergic agitation (antipsychotics acceptable for stimulants, avoided in anticholinergic toxicity) and avoid benzodiazepines alone in delirium or the elderly (except alcohol or sedative withdrawal).
Capacity (clinical, decision-specific) = communicate a choice, understand, appreciate, reason; competence is a legal status decided by a court.
Involuntary hold requires danger to self, danger to others, or grave disability; it is time-limited (often 72 h) and does not authorize forced non-emergency treatment.
Prior attempt predicts suicide and prior violence predicts violence; under Tarasoff, a credible threat to an identifiable victim creates a duty to protect (warn, notify police, hospitalize).

The hyperthermic toxidromes

Three look-alikes. Serotonin syndrome, neuroleptic malignant syndrome (NMS), and anticholinergic toxicity all produce fever, tachycardia, and altered mental status. Two bedside findings separate them: neuromuscular tone (clonus vs rigidity) and skin moisture (sweaty vs dry).

Serotonin syndrome vs NMS vs anticholinergic toxicity

Feature	Serotonin syndrome	NMS	Anticholinergic toxicity
Cause	Serotonergic drugs, often combined	Dopamine antagonists or abrupt dopamine-agonist withdrawal	Antihistamines, TCAs, antipsychotics, atropine
Onset	Rapid: hours, within 24 hours	Slow: over days	Within hours of ingestion
Neuromuscular	Clonus, hyperreflexia (legs > arms), myoclonus, tremor	Lead-pipe rigidity, hyporeflexia	Normal tone
Skin and pupils	Diaphoretic; dilated pupils	Diaphoretic	DRY, hot, flushed; dilated pupils
Other clues	Diarrhea, hyperactive bowel sounds	Very high CK, leukocytosis, rhabdomyolysis	Urinary retention, ileus, delirium
Treatment	Stop the agent, supportive care, cyproheptadine	Stop the agent, cooling, dantrolene, bromocriptine	Supportive; physostigmine if severe

DRY skin is the key discriminator: serotonin syndrome and NMS cause profuse sweating.

Serotonin syndrome reflects excess serotonergic activity, usually from combining agents: an SSRI plus an MAOI, tramadol, linezolid, triptans, or dextromethorphan. The triad is neuromuscular hyperactivity, autonomic instability (hyperthermia, tachycardia, diaphoresis, mydriasis), and altered mental status. The antidote is cyproheptadine, a 5-HT2A antagonist; benzodiazepines help control agitation and tremor.

NMS is an idiosyncratic reaction to dopamine antagonists (antipsychotics) or abrupt withdrawal of a dopamine agonist such as levodopa; the withdrawal form (parkinsonism-hyperpyrexia syndrome) is treated by restarting the dopaminergic drug. Its tetrad is hyperthermia, generalized lead-pipe rigidity, autonomic instability, and altered mental status, with markedly elevated CK, leukocytosis, and rhabdomyolysis that can cause acute kidney injury.

Anticholinergic toxicity is remembered as hot as a hare (hyperthermia), dry as a bone (anhidrosis, dry mucosa), red as a beet (flushing), blind as a bat (mydriasis, blurred vision), and mad as a hatter (delirium), plus urinary retention and ileus.

Lithium and antidepressant emergencies

>1.5 mEq/Llithium toxicity develops

>4 mEq/Lwith impaired kidney function, >5 mEq/L, or severe neurologic or cardiac signs: hemodialysis

Lithium toxicity starts with coarse tremor, GI upset, and ataxia, progressing to confusion, seizures, and arrhythmia at higher levels. Precipitants all reduce renal lithium clearance: dehydration, NSAIDs, thiazide diuretics, ACE inhibitors, and renal failure. Stop lithium and give IV isotonic fluids; hemodialysis is indicated for a level above 4 mEq/L with impaired kidney function, a level above 5 mEq/L, or decreased consciousness, seizures, or dysrhythmias at any level (EXTRIP). Activated charcoal does not bind lithium.

Antidepressant discontinuation syndrome. Abruptly stopping an SSRI or SNRI, especially short-half-life paroxetine or venlafaxine, causes FINISH: Flu-like symptoms, Insomnia, Nausea, Imbalance, Sensory disturbances (electric-shock "brain zaps"), and Hyperarousal. It is unpleasant but not dangerous, and tapering prevents it. Fluoxetine, with its long half-life, carries the lowest risk.

Other drug emergencies. MAOIs taken with tyramine-rich foods (aged cheese, cured meats) cause a hypertensive crisis treated with phentolamine; allow a washout of at least 2 weeks when switching between an MAOI and an SSRI (5 weeks after fluoxetine). TCA overdose causes anticholinergic signs, seizures, and QRS widening, treated with sodium bicarbonate.

Acute agitation and ECT

De-escalate, then medicate. Verbal de-escalation and a safe environment come first; restraints are a last resort. If medication is needed, give an antipsychotic (haloperidol) with or without a benzodiazepine (lorazepam).

Delirium and the elderly: avoid benzodiazepines alone, which cause paradoxical disinhibition and oversedation and can worsen delirium (except alcohol or sedative withdrawal, where a benzodiazepine is the treatment).
Stimulant or anticholinergic agitation: benzodiazepines are often preferred. For stimulant agitation, a parenteral antipsychotic (droperidol or haloperidol) alone or with a benzodiazepine, or ketamine, is also acceptable (ACEP 2023). Avoid antipsychotics mainly in anticholinergic toxicity, where they add anticholinergic effects and lower the seizure threshold.

Electroconvulsive therapy (ECT) is the emergency treatment when a rapid, definitive response is needed: severe, refractory, or psychotic depression; catatonia (typically after a lorazepam trial fails); acute suicidality; refusal to eat or drink; and severe depression or mania in pregnancy. It is highly effective, its main adverse effect is transient memory loss, and there are no absolute contraindications.

Capacity and involuntary treatment

Decision-making capacity is determined by a physician, is specific to each decision, and can fluctuate. It requires 4 elements:

Communicate a choiceClearly state a decision.
UnderstandGrasp the relevant facts.
AppreciateApply them to one's own situation and consequences.
ReasonWeigh the options logically.

Four components of capacity

Capacity vs competence

Feature	Capacity	Competence
Determined by	A physician (clinical judgment)	A court (legal judgment)
Scope	Decision-specific; can change over time	Global legal status
If absent	A surrogate decides	A court-appointed guardian decides

A patient with capacity may refuse treatment even when the choice seems unwise, and a psychiatric diagnosis alone does not remove capacity.

Involuntary hospitalization is justified on 3 grounds: danger to self, danger to others, or grave disability (inability to meet basic needs because of mental illness). Holds are time-limited, commonly 72 hours, for evaluation. An involuntary hold does not automatically permit forced non-emergency treatment, which requires further legal process.

Suicide, violence, and the duty to protect

Suicide risk. Ask directly; asking does not increase risk. The strongest predictor of completed suicide is a prior attempt; other factors are hopelessness, a plan with lethal means, male sex, and firearm access.

Violence risk. The strongest predictor of violence is a history of prior violence. Assess intent, plan, target, and means.

Tarasoff duty to protect. When a patient makes a credible threat against an identifiable victim, the clinician must take reasonable steps to protect that person: warning the victim, notifying police, or hospitalizing the patient. This is a recognized exception to confidentiality.