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Nervous

Antipsychotics

High-yield Verified · Jul 2026

Prototype: haloperidol

Typical (first-generation) and atypical (second-generation) agents that quiet psychosis by blocking dopamine.

How it works in the body

The system involved, what goes wrong, and how the drug and body interact.

01 Psychosis and the dopamine hypothesis

Psychosis — hallucinations, delusions, disordered thinking — is linked to too much dopamine signaling in one brain pathway (the mesolimbic system). Antipsychotics work by blocking dopamine D2 receptors, dialing down that overactive signaling and easing the "positive" symptoms.

The problem is that dopamine does other jobs in other pathways. Block it everywhere and you get predictable collateral effects: movement disorders (the motor pathway), elevated prolactin (the pituitary pathway), and blunting of "negative" symptoms. Understanding *which pathway* explains *which side effect* is the key to this class.

D2 blockade helps psychosis (mesolimbic) but disrupts movement (nigrostriatal) and prolactin (tuberoinfundibular).

02 Typical vs atypical — trading one side-effect profile for another

Typical (first-generation) agents like haloperidol are strong, relatively "pure" D2 blockers — very effective on positive symptoms but with the highest risk of movement disorders (EPS) and prolactin elevation. Atypical (second-generation) agents like risperidone, olanzapine, quetiapine block D2 *and* serotonin (5-HT2A) receptors, which reduces EPS but shifts the burden to metabolic side effects — weight gain, high blood sugar, and dyslipidemia.

So the choice is a trade: typicals risk the *movement* problems, atypicals risk the *metabolic* ones. Clozapine is the most effective agent for treatment-resistant schizophrenia and causes almost no EPS — but carries a unique, dangerous risk that mandates blood monitoring.

03 The reactions you must not miss — EPS, NMS, and clozapine

Extrapyramidal symptoms (EPS) appear on a timeline: acute dystonia (muscle spasms, hours–days), akathisia (inner restlessness), parkinsonism (tremor, rigidity, days–weeks), and tardive dyskinesia — late, repetitive involuntary movements (lip-smacking, tongue-thrusting) that may be irreversible, which is why long-term use is watched closely.

The emergency is neuroleptic malignant syndrome (NMS) — a rare but life-threatening reaction of high fever, "lead-pipe" rigidity, altered consciousness, autonomic instability, and elevated CK. Stop the drug and treat supportively (dantrolene/bromocriptine). Separately, clozapine can cause agranulocytosis (loss of infection-fighting white cells), requiring regular ANC (absolute neutrophil count) monitoring, plus myocarditis and seizure risk.

EPS unfold over a timeline; NMS is the febrile-rigidity emergency to recognize immediately.

Drug names

Generic Brand
haloperidol Haldol
risperidone Risperdal
olanzapine Zyprexa
quetiapine Seroquel
clozapine Clozaril

Indications

  • Schizophrenia and other psychotic disorders
  • Bipolar mania; adjunct in depression (some atypicals)
  • Acute agitation; Tourette syndrome, severe nausea (haloperidol); treatment-resistant schizophrenia (clozapine)

Mechanism of action

Block dopamine D2 receptors (reducing mesolimbic overactivity → ↓ positive symptoms). Atypical (second-generation) agents also block serotonin 5-HT2A receptors, which lessens extrapyramidal effects but increases metabolic effects. Many also block muscarinic, histaminic, and alpha-adrenergic receptors (sedation, anticholinergic, orthostasis).

In plain terms
They turn down overactive dopamine signaling in the brain, quieting hallucinations and delusions.

Therapeutic effects — what you'll see working

Antipsychotic benefit builds over days to weeks; agitation may settle sooner. Success is fewer/less-distressing psychotic symptoms — balanced against constant surveillance for movement, metabolic, and (with clozapine) hematologic harm.

↓ Positive symptoms Calmer, organized thinking
↓ Positive symptoms
D2 blockade in the mesolimbic pathway reduces hallucinations, delusions, and disordered thinking — the most reliable effect of the class.
Calmer, organized thinking
Over weeks, agitation and thought disorganization improve, aiding function and adherence. Atypicals may modestly help negative symptoms and mood.

Adverse effects

Every major adverse effect maps to a receptor: D2 (EPS, prolactin, NMS), 5-HT2A/H1/M (metabolic, sedation, anticholinergic), and alpha (orthostasis) — plus clozapine’s unique hematologic risk.

Caution: Common
Sedation, weight gain, metabolic changes (↑ glucose/lipids), orthostatic hypotension, anticholinergic effects, hyperprolactinemia (galactorrhea, menstrual changes).
Atypicals (especially olanzapine, clozapine, quetiapine) drive weight gain and metabolic syndrome — monitor weight, glucose, and lipids. Typicals raise prolactin (breast changes, sexual/menstrual effects). Sedation, dry mouth, constipation, and orthostasis come from histamine, muscarinic, and alpha blockade.
Warning: Serious Hold & notify
EPS (acute dystonia, akathisia, parkinsonism, tardive dyskinesia — possibly irreversible); QT prolongation; seizure threshold lowering; clozapine → agranulocytosis, myocarditis.
EPS are dose-related and highest with typicals; tardive dyskinesia may be permanent, so use the lowest effective dose and reassess. Several agents prolong QT. Clozapine uniquely causes agranulocytosis — mandatory ANC monitoring (baseline ≥ 1500/µL, then on a set schedule) — along with myocarditis, severe constipation/ileus, and seizures.
Black-box warning — most severe: ■ Boxed warning · elderly dementia + NMS emergency Report immediately
Increased mortality when used for dementia-related psychosis in elderly patients (all antipsychotics). NMS is a separate medical emergency.
All antipsychotics carry a boxed warning: elderly patients with dementia-related psychosis have a ~1.6–1.7× higher risk of death (largely cardiovascular/infectious) — antipsychotics are not approved for this use. Clozapine adds boxed warnings for agranulocytosis, seizures, myocarditis, and orthostatic hypotension. Neuroleptic malignant syndrome — fever, rigidity, altered consciousness, ↑CK — is a life-threatening emergency: stop the drug and treat immediately.

Contraindications

The contraindications flag the patients in whom D2 blockade or the receptor side effects are especially dangerous.

Dementia-related psychosis in the elderly
Increased mortality — the boxed warning; antipsychotics are not approved for this population.
History of neuroleptic malignant syndrome
Re-exposure can trigger a recurrent, potentially fatal reaction.
Parkinson's disease / Lewy body dementia (typical agents)
D2 blockade worsens the underlying dopamine deficit, and these patients are exquisitely sensitive to antipsychotics.
Prolonged QT / significant cardiac disease; severe CNS depression use caution
Several agents prolong QT and add sedation, risking arrhythmia and respiratory depression.
Clozapine: prior agranulocytosis / low ANC; uncontrolled seizures use caution
Clozapine can suppress the bone marrow and lower the seizure threshold — it requires regular ANC monitoring.

Labs & levels

Test Therapeutic / normal Toxic / critical
Clozapine — absolute neutrophil count (ANC) Weekly for the first 6 months, then less frequently (agranulocytosis surveillance) Normal range Baseline ≥ 1500/µL (≥ 1000 for benign ethnic neutropenia) < 500/µL = severe neutropenia — stop clozapine

Nursing considerations

The RN-specific layer — each action paired with the reason it matters.

Monitoring
Assess for EPS at baseline and regularly (use the AIMS scale for tardive dyskinesia); report new involuntary movements.
Why: Early EPS are treatable; tardive dyskinesia may be irreversible, so catching it early guides dose reduction or a switch.
Monitor weight, BMI, fasting glucose, and lipids (especially atypicals).
Why: Second-generation agents cause metabolic syndrome; tracking it allows early intervention.
For clozapine, ensure regular ANC monitoring (baseline ≥ 1500/µL); hold and report a falling ANC.
Why: Agranulocytosis is clozapine’s signature lethal risk; scheduled ANC checks catch it before infection is fatal.
Recognize NMS — high fever, rigidity, altered mental status, autonomic instability, ↑CK — as an emergency: stop the drug and get help.
Why: NMS is rapidly life-threatening; prompt discontinuation and supportive care are essential.
Patient teaching
Explain the effect may take days to weeks, and to not stop abruptly.
Why: Full antipsychotic benefit is delayed, and abrupt discontinuation can cause relapse or withdrawal effects.
Rise slowly (orthostasis), report muscle stiffness, fever, restlessness, or abnormal movements, and attend metabolic/blood monitoring.
Why: These teach the patient to catch orthostasis, NMS, EPS, and (clozapine) marrow suppression early.

Sources

Educational summary for nursing students. Always verify against current prescribing information and your institution's protocols before administering. Not medical advice.