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Clozapine Side Effects

The most commonly reported side effects of clozapine include neutropenia, hospitalisation, and death, based on 127,154 FDA adverse event reports from 2004 to 2025. 2.9% of reports found the drug to be ineffective.

#1 Reported: NeutropeniaAll side effects ↓Top Co-Medication: OlanzapineDrug interactions ↓79% of Reports Are AdultDemographics ↓

Clozapine side effects

Percentages show how often each reaction appears relative to total reports for clozapine.

1
Neutropenia14.8%18,878
2
Hospitalisation9.7%12,334
3
Death8.4%10,652
4
Schizophrenia3.4%4,295
5
Drug Ineffective2.9%3,648
6
White Blood Cell Count Decreased2.9%3,641
7
Off Label Use2.8%3,593
8
White Blood Cell Count Increased2.8%3,592
9
Neutrophil Count Increased2.8%3,571
10
Neutrophilia2.5%3,147
11
Malaise2.4%3,004
12
Treatment Noncompliance2.2%2,735
13
Haemoglobin Decreased2.0%2,582
14
Pneumonia2.0%2,543
15
Neutrophil Count Decreased2.0%2,543

These are voluntary reports and do not establish that clozapine caused these reactions.

Report severity

94.6%Serious120,309 reports
43.2%Hospitalizations54,988 reports
18.2%Fatal23,102 reports

Seriousness is determined by the reporter, not by OpenClaim.

Clozapine drug interactions

Other drugs that appear in adverse event reports alongside clozapine. Drugs flagged as a suspected cause appear in the first column. Drugs taken at the same time but not suspected appear in the second.

Also suspected

1
Olanzapine4.4%5,592
2
Aripiprazole3.5%4,402
3
Quetiapine-fumarate3.2%4,045
4
Risperidone3.0%3,876
5
Haloperidol1.8%2,280
6
Paliperidone1.3%1,647
7
Lithium1.3%1,633
8
Lorazepam1.2%1,557
9
Amisulpride1.2%1,470
10
Sertraline-hydrochloride1.1%1,434
11
Valproic-acid1.0%1,266
12
Diazepam1.0%1,226
13
Levodopa0.8%1,062
14
Carbidopa0.8%1,021
15
Valproate-sodium0.8%1,006

Taken alongside

1
Lorazepam2.7%3,429
2
Metformin2.2%2,846
3
Olanzapine2.2%2,771
4
Lithium2.1%2,660
5
Clonazepam2.1%2,630
6
Risperidone2.1%2,628
7
Haloperidol1.9%2,468
8
Aripiprazole1.9%2,437
9
Quetiapine-fumarate1.9%2,407
10
Levothyroxine-sodium1.9%2,393
11
Acetaminophen1.9%2,356
12
Divalproex-sodium1.8%2,324
13
Omeprazole1.8%2,313
14
Atorvastatin-calcium1.7%2,146
15
Aspirin1.6%1,979

Co-occurrence in adverse event reports does not establish a drug interaction. Patients often take multiple medications, and these lists reflect prescribing patterns rather than causal relationships. Consult a healthcare provider about potential drug interactions.

Who reports clozapine side effects

34.5% of clozapine adverse event reports involve female patients and 54.0% involve male patients. The largest age group is adult at 79%. These figures reflect who reports side effects, not underlying risk.

Sex

Female34.5%
Male54.0%
Unknown11.5%

Age group

< 20.3%
2–110.3%
12–172.0%
18–6479.0%
65+18.5%

What is clozapine used for

Conditions and purposes for which patients were taking clozapine when the adverse event was reported.

22q11.2 Deletion Syndrome22q11.2 Deletion SyndromeAbnormal BehaviourAbnormal DreamsAccidentAccidental ExposureAccidental Exposure To ProductAccidental Exposure To Product By ChildAccidental OverdoseAcute Lymphocytic LeukaemiaAcute PsychosisAdjustment Disorder With Depressed MoodAdverse EventAffect LabilityAffective Disorder

Showing 15 of 653 indications

Clozapine brand names and reporting trend

Clozapine is sold under the brand name Clozaril.

Brand names

Clozaril107,220

Quarterly reports (2004–2025)

20052010201520202025

An upward trend reflects increased FAERS reporting overall, not necessarily increased risk.

Taking clozapine with another medication?

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