Clozapine
Key Points
- Clozapine is reserved for treatment-resistant schizophrenia — only when ≥2 other antipsychotics have failed.
- Requires enrollment in the FDA REMS program due to risk of life-threatening agranulocytosis.
- ANC monitoring: weekly × 6 months → every 2 weeks × 6 months → monthly if stable.
- Only 1 week of medication dispensed at a time (linked to REMS compliance and ANC values).
- Never stop abruptly — abrupt withdrawal causes acute psychosis; must taper over 2 weeks.
Classification
| Parameter | Information |
|---|---|
| Drug class | Second-generation (atypical) antipsychotic |
| Mechanism | Blocks D2 dopamine + 5-HT2 serotonin receptors; additional neuroreceptor binding |
| Indication | Treatment-resistant schizophrenia (failure of ≥2 antipsychotics) |
| Schedule | REMS program; pharmacy dispenses 1-week supply at a time |
REMS Program (Risk Evaluation and Mitigation Strategy)
The FDA requires clozapine to be distributed only through the REMS program because of the risk of agranulocytosis — a potentially life-threatening suppression of neutrophils (white blood cells) that dramatically increases infection risk.
ANC Monitoring Schedule
| Phase | Monitoring Frequency |
|---|---|
| First 6 months | Weekly ANC |
| Months 7–12 | Every 2 weeks |
| After 12 months (if stable) | Every 4 weeks (monthly) |
| If ANC becomes abnormal | Intensified monitoring per REMS algorithm |
Hold clozapine if ANC <500/µL (severe neutropenia) or ANC <1,500/mm³ (clinical threshold for enhanced monitoring).
Early signs of agranulocytosis — patient must report immediately:
- Fever
- Sore throat
- Flu-like symptoms
Adverse Effects
Agranulocytosis (Black Box Warning)
- Rare but life-threatening bone marrow suppression
- ANC monitoring is mandatory; REMS enrollment required
Metabolic Effects
| Effect | Monitoring |
|---|---|
| Weight gain | BMI and weight at baseline and annually |
| Hyperglycemia | Fasting blood glucose at baseline and annually |
| Hyperlipidemia | Fasting lipid panel at baseline and annually |
| Metabolic syndrome | Waist circumference, BP, glucose, triglycerides, HDL |
Seizures
- Dose-dependent seizure risk — clozapine lowers the seizure threshold
- Higher doses carry greater seizure risk; lowest effective dose is preferred
Constipation (Serious Risk)
- Anticholinergic effect → intestinal hypomotility
- Can progress to bowel obstruction, intestinal ischemia, or necrotizing colitis if untreated
- Inpatient: auscultate bowel sounds every 4 hours
- Notify provider immediately if unable to move bowels; stool softeners may be ordered
Anticholinergic Effects
Dry mouth, constipation, blurred vision, urinary retention, tachycardia
Other Effects
- Sedation, dizziness, orthostatic hypotension (falls risk)
- Nausea, vomiting
- Myocarditis risk (especially in early weeks of treatment)
- Decreased risk of extrapyramidal side effects (EPS), tardive dyskinesia, and NMS compared to first-generation antipsychotics
Nursing Considerations
Before starting:
- Confirm REMS enrollment
- Baseline CBC with ANC, ECG, metabolic labs (glucose, lipids), liver/renal function, BMI, blood pressure
During therapy:
- Monitor ANC per REMS schedule; document all values
- Monitor for fever, sore throat, flu-like symptoms (agranulocytosis indicators)
- Assess mental status for therapeutic effectiveness (decreased hallucinations, improved self-care)
- Monitor for constipation — bowel sounds q4h (inpatient)
- Assess for EPS using validated scales (AIMS, Simpson-Angus Scale)
Never Abruptly Discontinue
Stopping clozapine suddenly causes acute psychosis/rebound. If discontinuation is needed, taper over a minimum of 2 weeks under provider guidance.
Patient Education
- Report fever, sore throat, or flu-like symptoms immediately — potential agranulocytosis
- Get weekly blood tests (first 6 months) without skipping — medication cannot be dispensed without current lab results
- Only 1 week of medication dispensed at a time
- Drink ≥64 oz of water daily; increase dietary fiber and exercise (constipation prevention)
- Report difficulty moving bowels immediately
- Avoid alcohol and CNS depressants (increased sedation)
- Rise slowly (orthostatic hypotension); do not drive until response to medication is known
- Do not stop medication without provider guidance — taper is required
- Full therapeutic benefit may take weeks to months
Related Concepts
- antipsychotics — Drug class overview including first- and second-generation comparisons.
- mental-health-and-mental-illness — Schizophrenia as a serious psychiatric illness requiring long-term treatment.
- leukopenia-and-neutropenia — Agranulocytosis as a severe form of neutropenia.
- psychotropic-medications — Broad category including antipsychotic drug class.
- therapeutic-communication — Therapeutic nurse-patient relationship in supporting medication adherence.
Self-Check
- A patient on clozapine calls the clinic reporting a fever and sore throat for 2 days. What is the nurse’s priority action?
- What is the ANC monitoring schedule for the first 12 months of clozapine therapy?
- Why is it critical to never stop clozapine abruptly?