Generic name
Trihexyphenidyl hydrochloride: adverse event reports filed with FDA
609 reports list it as a suspect or interacting product, 2004–2026. Also reported as Trihexyphenidyl Hcl, Trihexyphenidyl Hydrochloride Tablets.
- 609
- reports as suspect product
- 0% of all reports · about 27 a year
- 88
- reports, 12 months to June 2026
- 60 in the 12 months before
- 95.9%
- marked serious by the reporter
- 57.4% across all reports
- 23.2%
- record death among outcomes, as reported
- 141 reports · not verified by FDA
609 adverse event reports received by FDA list trihexyphenidyl hydrochloride, a generic name as a suspect or interacting product, from February 2004 to June 2026. A further 901 reports list it only as a concomitant medication, and those are not counted in the figures on this page.
In the 12 months to June 2026, 88 reports listed it, up 47% from 60 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 27 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 MedDRA terms listed most often are drug interaction (7.7%), coma (7.4%) and ischaemic stroke (6.2%). A report can list several reactions, so shares add to more than 100%; 185 different terms appear across these reports. Drug interaction is recorded in 7.7% of these reports, against 0.8% of all reports in the database.
95.9% of the reports are marked serious by the reporter; 23.2% record death among the outcomes and 52.7% record hospitalisation, as reported. 34.5% of the reports came from physicians, and the largest patient age group is 45 to 64 (30.7%). 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 hydrochloride reports recording the termall reports in the database
- Drug interactionan interaction between medicines7.7%47
- Coma7.4%45
- Ischaemic stroke6.2%38
- Off label useused for a purpose or in a way not on the label5.9%36
- Respiratory distressdifficulty breathing5.7%35
- Nauseafeeling sick5.4%33
- Respiratory failurethe lungs could not supply enough oxygen5.1%31
- Areflexia4.9%30
- Brain scan abnormal4.9%30
- Cerebral artery thrombosis4.8%29
- Cerebrovascular accidentstroke4.8%29
- Disease recurrencethe disease came back4.8%29
- Facial paralysis4.8%29
- Hemiplegia4.8%29
- Product use issuea problem in how the product was used3.8%23
- Drug abusemisuse of a medicine3.4%21
- Condition aggravatedthe condition being treated got worse3.3%20
- Wrong patient received product3.3%20
- Falla fall3.1%19
- Agitationrestlessness2.6%16
- Confusional stateconfusion2.6%16
- Dysphagiadifficulty swallowing2.5%15
- Extrapyramidal disordermovement problems such as stiffness or tremor2.5%15
- Intestinal obstructiona blocked bowel2.5%15
- Acute kidney injurysudden loss of kidney function2.1%13
- Colitis ischaemic2.1%13
- Intentional overdosea deliberate overdose2.1%13
- Toxicity to various agentspoisoning or toxic effect of one or more substances2.1%13
- Wrong patient2.1%13
Top 30 of 185 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. 11.7% of reports give the United States as the country of the event or reporter.
Reason for use recorded
| Indication as recorded (MedDRA) | Reports | Share |
|---|---|---|
| Parkinsonism | 41 | 6.7% |
| Extrapyramidal disorder | 24 | 3.9% |
| Schizophrenia | 23 | 3.8% |
| Parkinson's disease | 12 | 2% |
| Wrong patient | 11 | 1.8% |
| Wrong patient received product | 10 | 1.6% |
The indication field is filled in by the reporter and is often blank; shares are of all 609 reports.
In context
| Measure | Trihexyphenidyl hydrochloride | All reports |
|---|---|---|
| Reports as suspect product | 609 | 20,646,523 |
| Share of that pool | — | 0% |
| Reports, latest 12 months | 88 | 1,332,454 |
| Marked serious | 95.9% | 57.4% |
| Death recorded among outcomes, per 1,000 reports | 232 | 91 |
| Hospitalisation recorded, per 1,000 reports | 527 | 213 |
| Consumer-filed share | 10.3% | 45.8% |
| Top term, share of reports | Drug interaction 7.7% | 0.8% |
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 hydrochloride reports
How many adverse event reports has FDA received for Trihexyphenidyl hydrochloride?
609 reports list Trihexyphenidyl hydrochloride as a suspect or interacting product in the openFDA FAERS release of 28 Sep 2026, covering reports received through June 2026. 88 of them arrived in the latest 12 months. Another 901 list it only as a concomitant medication.
What reactions are recorded in Trihexyphenidyl hydrochloride reports?
drug interaction (7.7%), coma (7.4%), ischaemic stroke (6.2%), off label use (5.9%) and respiratory distress (5.7%). 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 hydrochloride was responsible.
How serious are the reports?
95.9% are marked serious by the reporter. Among the outcomes recorded, 23.2% of reports include death and 52.7% 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?
physician (34.5%), other health professional (33.7%) and pharmacist (14.1%). Most reports reach FDA through the manufacturer, which must forward reports it receives.
Are reports for Trihexyphenidyl hydrochloride rising?
88 reports in the 12 months to June 2026, up 47% from 60 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 hydrochloride 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 hydrochloride?
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 hydrochloride as a suspect or interacting product; reports listing it only as a concomitant medication (901) 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.