Quetiapine vs Clonazepam: side effects in FDA adverse event reports
At a glance
| Quetiapine | Clonazepam | |
|---|---|---|
| Drug class | – | Benzodiazepine |
| Brand names | Quetiapine Extended Release | – |
| FAERS reports | 191,471 | 159,258 |
| Serious | 79% | 68% |
| Death outcome | 28,195 | 18,605 |
| 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 RISKS FROM CONCOMITANT USE WITH OPIOIDS; ABUSE, MISUSE, AND ADDICTION; and DEPENDENCE AND WITHDRAWAL REACTIONS Concomitant use of benzodiazepines and opioids ma |
Signals both drugs share
| Reaction | Quetiapine | Clonazepam | Label screen (A / B) |
|---|---|---|---|
| Neuroleptic malignant syndrome | 2,768 · PRR 33.0 | 703 · PRR 8.2 | Labeled — boxed warning / Not in label — unassessed |
| Cogwheel rigidity | 226 · PRR 29.7 | 141 · PRR 20.2 | Labeled adverse reaction / Not in label — unassessed |
| Diabetic neuropathy | 850 · PRR 22.4 | 273 · PRR 7.6 | Not in label — unassessed / Not in label — unassessed |
| Psychiatric decompensation | 357 · PRR 24.4 | 255 · PRR 19.7 | Not in label — unassessed / Not in label — unassessed |
| Stubbornness | 174 · PRR 73.1 | 151 · PRR 70.0 | 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
- 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 Clonazepam
- Rhinitis allergic — n=479, PRR 15.8 Labeled (related wording)
- Substance use disorder — n=301, PRR 14.2 Labeled adverse reaction
- Depression suicidal — n=229, PRR 9.3 Labeled (related wording)
- Depressive symptom — n=219, PRR 8.7 Labeled adverse reaction
- Hostility — n=144, PRR 7.8 Labeled adverse reaction
Common questions
Which has more reported side effects, Quetiapine or Clonazepam?
Quetiapine has 191,471 FAERS reports and Clonazepam 159,258. 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 68%) is a better like-for-like signal of the kind of problems reported.
Which side effects do Quetiapine and Clonazepam share?
Both drugs carry disproportionality signals for neuroleptic malignant syndrome, cogwheel rigidity, diabetic neuropathy, psychiatric decompensation, stubbornness. Shared signals often reflect a shared drug class or the condition both are used for.
Is Quetiapine or Clonazepam 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.