What the label lists and what reports show
Clozapine side effects
Clozapine's FDA label: “Most common adverse reactions (≥5%) were: CNS reactions (sedation, dizziness/vertigo, headache, and tremor); cardiovascular reactions (tachycardia, hypotension, and syncope); …” FAERS holds 124,829 reports naming it through July 30, 2026; the reaction reported most often, leaving out the conditions it is used for, product-use terms and outcomes, is white blood cell count increased (4,507 reports).
- Generic listed
- Boxed warning
Check it at the source: the clozapine FDA label on DailyMed (effective June 6, 2025, HLS Therapeutics (USA), Inc.); the FDA FAERS public dashboard.
What does the patient leaflet say about side effects?
From the patient leaflet: What are the possible side effects of CLOZARIL?CLOZARIL can cause serious side effects, including: • See "What is the most important information I should know about CLOZARIL?" • falls. CLOZARIL may make you sleepy, dizzy, may cause a decrease in your blood pressure when changing positions, and can slow your thinking and motor skills which may lead to falls that can cause fractures or other injuries. • slow emptying of your stomach and intestines (decreased gastric motility). Severe constipation and bowel problems can happen and can lead to hospitalization, surgery, and death. You may not feel or be aware of constipation symptoms. Your healthcare provider will examine you for possible bowel problems. […]
Source: FDA drug label, NDA019758 (Heritage Life), as published by HLS Therapeutics (USA), Inc., effective June 6, 2025 (SPL set 90876802-0e3a-44c9-9ff7-1754dfbe736a), via openFDA; the full label on DailyMed
What does the label list?
From the label: adverse reactionsMost common adverse reactions (≥5%) were: CNS reactions (sedation, dizziness/vertigo, headache, and tremor); cardiovascular reactions (tachycardia, hypotension, and syncope); autonomic nervous system reactions (hypersalivation, sweating, dry mouth, and visual disturbances); gastrointestinal reactions (constipation and nausea); and fever.
Table 10. Adverse Reactions (≥2%) Reported in CLOZARIL-treated Patients (N=842) Across all CLOZARIL Studies (excluding the 2-year InterSePT™ Study)
| Body System Adverse Reaction * | †Rate based on population of approximately 1700 exposed during premarket clinical… CLOZARIL N=842 Percentage of Patients Central Nervous System |
|---|---|
| Drowsiness/Sedation | 39 |
| Dizziness/Vertigo | 19 |
| Headache | 7 |
| Tremor | 6 |
| Syncope | 6 |
| Disturbed Sleep/Nightmares | 4 |
| Restlessness | 4 |
| Hypokinesia/Akinesia | 4 |
| Agitation | 4 |
| Rigidity | 3 |
| Akathisia | 3 |
| Confusion | 3 |
| Fatigue | 2 |
| Insomnia | 2 |
| Hypotension | 9 |
| Hypertension | 4 |
| Constipation | 14 |
| Nausea | 5 |
| Abdominal Discomfort/Heartburn | 4 |
| Nausea/Vomiting | 3 |
| Vomiting | 3 |
| Diarrhea | 2 |
| Urinary Abnormalities | 2 |
| Salivation | 31 |
| Sweating | 6 |
Rows and numbers as the label prints them, under its own column headings (the first rows of a longer table where it runs on). A reaction in a trial table is not necessarily caused by the medicine, and trials differ from everyday use.
From the label: adverse reactions, continuedThe following adverse reactions are discussed in more detail in other sections of the labeling: • Severe Neutropenia [see Warnings and Precautions ( 5.1 )] • Orthostatic Hypotension, Bradycardia, and Syncope [see Warnings and Precautions ( 5.2 )] • Falls [see Warnings and Precautions ( 5.3 )] • Seizures [see Warnings and Precautions ( 5.4 )] • Myocarditis, Pericarditis, Cardiomyopathy, and Mitral Valve Incompetence [see Warnings and Precautions ( 5.5 )] • Increased Mortality in Elderly Patients with Dementia-Related Psychosis [see Warnings and Precautions ( 5.6 )] • Gastrointestinal Hypomotility with Severe Complications [See Warnings and Precautions ( 5.7) ] • Eosinophilia [see Warnings and Precautions ( 5.8 )] • QT Interval Prolongation [see Warnings and Precautions ( 5.9 )] • Metabolic Changes (Hyperglycemia and Diabetes Mellitus, Dyslipidemia, and Weight Gain) [see Warnings and Precautions ( 5.10 )] • Neuroleptic Malignant Syndrome [see Warnings and Precautions ( 5.11 )] • Hepatotoxicity [see Warnings and Precautions ( 5.12 )] • Fever [see Warnings and Precautions ( 5.13 )] • Pulmonary Embolism [see Warnings and Precautions ( 5.14 )] • Anticholinergic Toxicity [see Warnings and Precautions ( 5.15 )] • Interference with Cognitive and Motor Performance [see Warnings and Precautions ( 5.16 )] • Tardive Dyskinesia [see Warnings and Precautions ( 5.17 )] • Cerebrovascular …
Source: FDA drug label, NDA019758 (Heritage Life), as published by HLS Therapeutics (USA), Inc., effective June 6, 2025 (SPL set 90876802-0e3a-44c9-9ff7-1754dfbe736a), via openFDA; the full label on DailyMed
What do FAERS reports show?
124,829 reports list clozapine among the medicines taken, each a report of something that happened, not proof the medicine caused it; 22,310 are coded as a death and 54,629 as a hospital stay. Counts follow how widely a medicine is used and watched, and they are not a measure of how risky it is. Of the 18 reactions below, 6 are named by the same term (in US spelling) in the label's adverse reactions, warnings or patient leaflet; a reaction the label does not name may still be there under another word, and a report does not show that the medicine caused it.
Reports received each year
The 25 most reported reactions
Source: FDA Adverse Event Reporting System (FAERS) via openFDA, reports through July 30, 2026; reactions as MedDRA preferred terms
What next?
- Clozapine: the full record
- label, generics, price, shortages, recalls
- Report a side effect to the FDA
- MedWatch
- Side effects hub
- the most reported medicines and reactions