4.6 Medication Emergencies II: EPS, TD, Lithium Toxicity & Clozapine

Extrapyramidal symptoms, tardive dyskinesia, lithium toxicity, and clozapine's unique hematologic risk are the medication emergencies most likely to appear in an ANCC scenario item, because each has a specific, time-sensitive nursing response.

Extrapyramidal Symptoms (EPS)

EPS results from dopamine (D2) blockade in the nigrostriatal pathway, most often from FGAs but also possible with SGAs (especially risperidone at higher doses). Three distinct presentations occur, each with its own timeline and treatment:

The general progression is that dystonia appears earliest (hours to days), akathisia and pseudoparkinsonism follow over days to weeks, and tardive dyskinesia — described next — appears latest, after months to years of exposure. In older adults, anticholinergics such as benztropine carry their own risk of confusion, constipation, and falls, so amantadine is often favored for pseudoparkinsonism in this population per Beers Criteria guidance.

Tardive Dyskinesia (TD)

TD is a late-onset movement disorder that develops after months to years of antipsychotic exposure and presents with involuntary, repetitive movements — orofacial (lip smacking, tongue protrusion, grimacing) and choreoathetoid movements of the limbs or trunk. Unlike the acute EPS types above, TD is often irreversible even after the causative drug is stopped, which is why prevention and early detection matter so much.

Nurses screen for TD using the Abnormal Involuntary Movement Scale (AIMS), administered at baseline before starting an antipsychotic and then periodically (commonly every 6-12 months, more often in higher-risk patients) throughout treatment. Management options include switching to a lower-EPS-risk agent, reducing dose, and VMAT2 inhibitors (valbenazine, deutetrabenazine) — agents specifically FDA-approved to treat TD.

Lithium Toxicity Management

As covered in Section 4.3, lithium toxicity begins above 1.5 mEq/L and becomes severe/life-threatening above 2.0 mEq/L. Management is stepped by severity:

• Mild-to-moderate toxicity: hold the lithium dose, obtain a repeat level, provide IV isotonic fluids to support renal excretion, and monitor neurologic and cardiac status closely.
• Severe toxicity (very high levels, significant renal impairment, seizures, coma, or inability to tolerate oral/IV fluids): hemodialysis is the definitive treatment and can be lifesaving; it is strongly considered whenever the level is markedly elevated with severe neurologic or renal findings, regardless of the exact number, because clinical status — not the level alone — drives the decision.

Because dehydration, low sodium intake, NSAIDs, and thiazide diuretics all raise lithium levels, prevention through patient education remains the first line of defense.

Clozapine and Agranulocytosis

Clozapine is reserved for treatment-resistant schizophrenia — typically after at least two adequate trials of other antipsychotics have failed — because of its unique risk of agranulocytosis, a life-threatening drop in neutrophils that impairs the ability to fight infection. Clozapine is dispensed only through a REMS (Risk Evaluation and Mitigation Strategy) program that requires the prescriber, the pharmacy, and the patient to all be enrolled, and each ANC result must be verified and reported through the REMS system before the next supply can be dispensed.

ANC thresholds:

• Baseline ANC ≥1500/µL is required to start clozapine (≥1000/µL for patients with documented benign ethnic neutropenia).
• Monitoring frequency: weekly CBC/ANC for the first 6 months, then every 2 weeks for the next 6 months, then monthly thereafter if ANC has remained normal.
• ANC below 1000/µL: treatment is interrupted and monitoring intensifies until recovery.
• ANC below 500/µL (agranulocytosis): clozapine is discontinued immediately, a hematology consult is obtained, and the drug is not restarted without specialist guidance.

Clozapine also carries risk of myocarditis (highest in the first 6-8 weeks — assess for fever, tachycardia, chest pain, and dyspnea), dose-related seizures, and severe constipation that can progress to a potentially fatal bowel obstruction or ileus — a prophylactic bowel regimen is often started proactively rather than waiting for symptoms — along with sialorrhea, significant weight gain, and orthostatic hypotension. The nurse's monitoring role extends well beyond the ANC alone.

Clinical Application

A patient on haloperidol who suddenly cannot turn their neck and is gasping needs IM benztropine immediately — acute dystonia is a rapidly reversible emergency. A patient on clozapine whose weekly ANC returns at 420/µL needs the medication stopped today and an urgent hematology referral, not a "recheck next week."