Generic name
Trihexyphenidyl: adverse event reports filed with FDA
917 reports list it as a suspect or interacting product, 2009–2026.
- 917
- reports as suspect product
- 0% of all reports · about 52 a year
- 86
- reports, 12 months to June 2026
- 133 in the 12 months before
- 94%
- marked serious by the reporter
- 57.4% across all reports
- 13.7%
- record death among outcomes, as reported
- 126 reports · not verified by FDA
Between January 2009 and June 2026, 917 adverse event reports received by FDA list trihexyphenidyl, a generic name as a suspect or interacting product. Reports that mention it only as a concomitant medication (1,500) are left out of every figure here.
In the 12 months to June 2026, 86 reports listed it, down 35% from 133 in the 12 months before. FDA releases FAERS data quarterly, so the newest months are incomplete and grow in later releases. Over its reporting history that is about 52 reports a year and 0% of the 20,646,523 reports in the database. How many people take it is not in the data, so a count is not a rate of occurrence.
The reactions recorded most often are drug ineffective (17.6%), drug interaction (11.2%) and off label use (10.6%). A report can list several reactions, so shares add to more than 100%; 326 different terms appear across these reports. Drug ineffective is recorded in 17.6% of these reports, against 6.3% of all reports in the database.
94% of the reports are marked serious by the reporter; 13.7% record death among the outcomes and 44.9% record hospitalisation, as reported. 51.8% of the reports came from other health professionals, and the largest patient age group is 18 to 44 (34.1%). FDA states that "a causal relationship cannot be established between product and reactions listed in a report" and that for any given report "there is no certainty that a suspected drug caused the event."
Reports by month, five years
Reports by the month FDA received them. FDA releases FAERS data quarterly, so the newest months are incomplete and grow in later releases.
By year received
2026 covers reports received through June 2026 only.
Reactions recorded in the reports
share of Trihexyphenidyl reports recording the termall reports in the database
- Drug ineffectivethe medicine did not work as expected17.6%161
- Drug interactionan interaction between medicines11.2%103
- Off label useused for a purpose or in a way not on the label10.6%97
- Toxicity to various agentspoisoning or toxic effect of one or more substances9.9%91
- Confusional stateconfusion6%55
- Dystoniainvoluntary muscle contractions5.8%53
- Hallucinationseeing or hearing things that are not there5.3%49
- Somnolencedrowsiness4.7%43
- Tremorshaking4.5%41
- Extrapyramidal disordermovement problems such as stiffness or tremor4.1%38
- Cognitive disorderproblems with thinking or memory4%37
- Overdosea dose above the recommended amount3.9%36
- Parkinsonism3.8%35
- Neuroleptic malignant syndromea rare severe reaction with fever and rigidity3.7%34
- Condition aggravatedthe condition being treated got worse3.3%30
- Sinus tachycardia3.3%30
- Product use in unapproved indicationused for a purpose not on the label3.2%29
- Suicide attempta suicide attempt3.2%29
- Intentional product misusedeliberate use not as intended3.1%28
- Gait disturbancedifficulty walking2.7%25
- Oedema peripheralswelling of the legs, ankles or hands2.6%24
- Treatment failurethe treatment did not work2.6%24
- Drug abusemisuse of a medicine2.5%23
- Respiratory failurethe lungs could not supply enough oxygen2.5%23
- Therapy non-responderthe treatment did not work2.5%23
- Deliriumsudden confusion2.4%22
- Dizzinesslight-headedness or unsteadiness2.4%22
- Disorientation2.3%21
- Tardive dyskinesiainvoluntary repetitive movements2.3%21
Top 30 of 326 MedDRA preferred terms recorded across these reports, with a plain-language gloss where one is available. One report can record several terms. The hollow bar is the share of all reports in the database; it describes the reports, not the patients. FDA states that adverse event reports "represent a small percentage of total usage numbers of a product", that "common products may have a higher number of adverse events due to the higher total number of people using the product", and that the data "by themselves are not an indicator of the safety profile of the drug or biologic."
Outcomes recorded
Outcome flags as the reporter set them; a report can carry several, and "other serious" is FDA's own category for serious reports outside the named outcomes. Grey bar: all 20,646,523 reports. FDA has not verified any outcome and states that the reports "cannot be used to estimate the incidence of these events."
Patients and reporters
Patient age
Patient sex
Who reported
Age and sex as stated in the report; the reporter's qualification is the primary source recorded by FDA. 24.5% of reports give the United States as the country of the event or reporter.
Reason for use recorded
| Indication as recorded (MedDRA) | Reports | Share |
|---|---|---|
| Dystonia | 73 | 8% |
| Schizophrenia | 70 | 7.6% |
| Parkinson's disease | 37 | 4% |
| Parkinsonism | 16 | 1.7% |
| Bipolar disorder | 14 | 1.5% |
| Extrapyramidal disorder | 13 | 1.4% |
The indication field is filled in by the reporter and is often blank; shares are of all 917 reports.
Drugs most often listed in the same reports
| Drug (any role in the report) | Reports | Share of Trihexyphenidyl reports |
|---|---|---|
| Clonazepam | 203 | 22.1% |
| Olanzapine | 157 | 17.1% |
| Risperidone | 155 | 16.9% |
| Diazepam | 148 | 16.1% |
| Haloperidol | 146 | 15.9% |
| Quetiapine | 106 | 11.6% |
| Lorazepam | 103 | 11.2% |
| Baclofen | 101 | 11% |
| Aripiprazole | 88 | 9.6% |
| Gabapentin | 87 | 9.5% |
Other products listed in reports where Trihexyphenidyl is a suspect product, whatever their own role. Co-listing means the two were recorded together; it says nothing about either product's part in the event. Only the 2,500 most-reported names are counted here.
In context
| Measure | Trihexyphenidyl | All reports |
|---|---|---|
| Reports as suspect product | 917 | 20,646,523 |
| Share of that pool | — | 0% |
| Reports, latest 12 months | 86 | 1,332,454 |
| Marked serious | 94% | 57.4% |
| Death recorded among outcomes, per 1,000 reports | 137 | 91 |
| Hospitalisation recorded, per 1,000 reports | 449 | 213 |
| Consumer-filed share | 6.9% | 45.8% |
| Top term, share of reports | Drug ineffective 17.6% | 6.3% |
Shares are of reports, not of patients treated. The number of people taking a product is not in the data, so none of these figures is a rate, and differences between columns reflect who takes a product, who reports and how long it has been sold. FDA states that adverse event reports "represent a small percentage of total usage numbers of a product", that "common products may have a higher number of adverse events due to the higher total number of people using the product", and that the data "by themselves are not an indicator of the safety profile of the drug or biologic."
Questions about Trihexyphenidyl reports
How many adverse event reports has FDA received for Trihexyphenidyl?
917 reports list Trihexyphenidyl as a suspect or interacting product in the openFDA FAERS release of 28 Sep 2026, covering reports received through June 2026. 86 of them arrived in the latest 12 months. Another 1,500 list it only as a concomitant medication.
What reactions are recorded in Trihexyphenidyl reports?
drug ineffective (17.6%), drug interaction (11.2%), off label use (10.6%), toxicity to various agents (9.9%) and confusional state (6%). These are MedDRA preferred terms coded from what the reporter described; a report can list several, and a term's presence is not a finding that Trihexyphenidyl was responsible.
How serious are the reports?
94% are marked serious by the reporter. Among the outcomes recorded, 13.7% of reports include death and 44.9% include hospitalisation. FDA has not verified these outcomes and states that the reports "cannot be used to estimate the incidence" of the events.
Who files these reports?
other health professional (51.8%), physician (35.6%) and consumer or non-health professional (6.9%). Most reports reach FDA through the manufacturer, which must forward reports it receives.
Are reports for Trihexyphenidyl rising?
86 reports in the 12 months to June 2026, down 35% from 133 in the 12 months before. FDA releases FAERS data quarterly, so the newest months are incomplete and grow in later releases. Counts also move with how many people take a product, its time on the market and publicity.
Do these reports show that Trihexyphenidyl was responsible for these reactions?
No. FDA states that "a causal relationship cannot be established between product and reactions listed in a report" and that for any given report "there is no certainty that a suspected drug caused the event." The reaction may relate to the condition being treated, to other medicines, or to something else.
Is this a list of the side effects of Trihexyphenidyl?
No. It is a count of what was reported to FDA. The adverse reactions observed in clinical studies are printed on the FDA-approved label, which a pharmacist or clinician can go through with you.
How do I report an adverse event?
Consumers and health professionals can report to FDA through MedWatch (Form FDA 3500 online, or 1-800-FDA-1088), or to the manufacturer, which must pass reports on. See the guide on how to report.
Where this comes from. Counts are built from the openFDA Drug Adverse Event (FAERS) bulk export released 28 Sep 2026, which holds reports FDA received through 30 Jun 2026. Drug names are as reported, resolved to the brand or generic name on the FDA label where openFDA's harmonisation matched them; classes are the pharmacologic class (EPC) from the label and the National Drug Code Directory of 17 Sep 2026. A report counts here when it lists Trihexyphenidyl as a suspect or interacting product; reports listing it only as a concomitant medication (1,500) are excluded. No report narrative, lot number, patient detail or reporter identity is published. See the methodology and sources; FDA's record is authoritative, and corrections are handled within five working days.
Drug data (FAERS) through 30 Jun 2026; device data (MAUDE) through 31 Aug 2026. Not medical advice.