Quetiapine vs Clozapine: side effects in FDA adverse event reports
At a glance
| Quetiapine | Clozapine | |
|---|---|---|
| Drug class | – | Atypical Antipsychotic |
| Brand names | Quetiapine Extended Release | – |
| FAERS reports | 191,471 | 124,826 |
| Serious | 79% | 95% |
| Death outcome | 28,195 | 22,310 |
| Boxed warning | Yes INCREASED MORTALITY IN ELDERLY PATIENTS WITH DEMENTIA-RELATED PSYCHOSIS; AND SUICIDAL THOUGHTS AND BEHAVIORS Increased Mortality in Elderly Patients with Dement | Yes WARNING: SEVERE NEUTROPENIA; ORTHOSTATIC HYPOTENSION, BRADYCARDIA, AND SYNCOPE; SEIZURE; MYOCARDITIS, PERICARDITIS, AND CARDIOMYOPATHY; INCREASED MORTALITY IN E |
Signals both drugs share
| Reaction | Quetiapine | Clozapine | Label screen (A / B) |
|---|---|---|---|
| Schizoaffective disorder | 362 · PRR 27.5 | 610 · PRR 86.6 | Likely indication confounding / Likely indication confounding |
| Anosognosia | 459 · PRR 162.2 | 498 · PRR 310.8 | Not in label — unassessed / Not in label — unassessed |
| Psychiatric decompensation | 357 · PRR 24.4 | 465 · PRR 52.4 | Not in label — unassessed / Not in label — unassessed |
Labeled signals distinctive to Quetiapine
- Type 2 diabetes mellitus — n=5,970, PRR 23.4 Labeled — boxed warning
- Neuroleptic malignant syndrome — n=2,768, PRR 33.0 Labeled — boxed warning
- Diabetic coma — n=886, PRR 49.8 Labeled (related wording)
- Peripheral venous disease — n=834, PRR 28.7 Labeled (related wording)
- Temperature regulation disorder — n=373, PRR 22.4 Labeled (related wording)
- Metabolic syndrome — n=364, PRR 31.0 Labeled (related wording)
- Anticholinergic syndrome — n=349, PRR 30.5 Labeled (related wording)
- Bezoar — n=335, PRR 35.0 Labeled adverse reaction
Labeled signals distinctive to Clozapine
- Granulocytopenia — n=2,616, PRR 141.2 Labeled adverse reaction
- Myocarditis — n=2,231, PRR 41.1 Labeled — boxed warning
- Salivary hypersecretion — n=1,844, PRR 37.9 Labeled adverse reaction
- Psychotic symptom — n=370, PRR 37.1 Labeled adverse reaction
- Benign ethnic neutropenia — n=114, PRR 1,565.3 Labeled — boxed warning
- Rebound psychosis — n=79, PRR 99.4 Labeled (related wording)
Common questions
Which has more reported side effects, Quetiapine or Clozapine?
Quetiapine has 191,471 FAERS reports and Clozapine 124,826. More reports does not mean more dangerous: volume follows how widely and how long a drug has been used, prescription vs over-the-counter status, and publicity. The seriousness share (79% vs 95%) is a better like-for-like signal of the kind of problems reported.
Which side effects do Quetiapine and Clozapine share?
Both drugs carry disproportionality signals for schizoaffective disorder, anosognosia, psychiatric decompensation. Shared signals often reflect a shared drug class or the condition both are used for.
Is Quetiapine or Clozapine safer?
FAERS cannot answer that: it has no denominator and no comparator. Use this page to see which risks are already on each label and which signals are unlabeled, then check the prescribing information and your clinician for your situation.
Sources: openFDA FAERS pair statistics (OpenPV build 2026-09-14), FDA labels via openFDA, openFDA count queries for seriousness and deaths. Pair chosen because it is a commonly searched comparison. Generated 2026-10-08.