MedDRA preferred term

Encephalopathy: adverse event reports recording this term

24,091 reports to FDA record it, 2004–2026; 0.1% of the database.

Read first · FDA's statement on these data

Adverse event reports submitted to FDA do not undergo extensive validation or verification. Therefore, a causal relationship cannot be established between product and reactions listed in a report. While a suspected relationship may exist, it is not medically validated and should not be the sole source of information for clinical decision making or other assumptions about the safety or efficacy of a product. Additionally, it is important to remember that adverse event reports represent a small percentage of total usage numbers of a product. Common products may have a higher number of adverse events due to the higher total number of people using the product. openFDA, FDA

FDA adds: "There is no certainty that the reported event (adverse event or medication error) was actually due to the product. FDA does not require that a causal relationship between a product and event be proven, and reports do not always contain enough detail to properly evaluate an event." The information in these reports "cannot be used to estimate the incidence of these events."

Do not rely on openFDA to make decisions regarding medical care. While we make every effort to ensure that data is accurate, you should assume all results are unvalidated.

Not medical advice. This site counts what was reported to FDA. Questions about a medicine or device belong with a pharmacist or clinician.

24,091
reports recording the term: 0.1% of all reports; 1,655
reports, 12 months to June 2026: 1,386 in the 12 months before; 99.3%
marked serious by the reporter: 57.4% across all reports; 20.8%
record death among outcomes, as reported: 9.1% across all reports

"Encephalopathy" is a MedDRA preferred term recorded in 24,091 adverse event reports received by FDA, 0.1% of the database, from January 2004 to June 2026. The term is chosen by whoever codes the report to match what the reporter described.

1,655 reports recorded it in the 12 months to June 2026, up 19% from 1,386 in the 12 months before. FDA releases FAERS data quarterly, so the newest months are incomplete and grow in later releases. Of reports recording this term, 99.3% are marked serious, 20.8% include death among the outcomes and 68.4% include hospitalisation, as reported.

The drugs listed most often as suspect products in those reports are Baclofen, Methotrexate and Tacrolimus. That order mostly follows how many reports each drug has overall; the table also gives the term's share within each drug's own reports. 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

FDA releases FAERS data quarterly, so the newest months are incomplete and grow in later releases.

Drugs listed as suspect products in these reports

Drug	Class	Reports with this term	Share of the drug's own reports
Baclofen	gamma-Aminobutyric acid-ergic agonist	911	4.2%
Methotrexate	Folate analog metabolic inhibitor	890	0.4%
Tacrolimus	Calcineurin inhibitor immunosuppressant	647	0.7%
Prednisone	Corticosteroid	630	0.3%
Cyclophosphamide	Alkylating drug	626	0.4%
Ifosfamide	Alkylating drug	611	3.3%
Acetaminophen	Nonsteroidal anti-inflammatory drug	584	0.7%
Dexamethasone	Corticosteroid	483	0.4%
Metronidazole	Nitroimidazole antimicrobial	416	1.7%
Etoposide	Topoisomerase inhibitor	408	0.7%
Levetiracetam	—	397	0.8%
Cytarabine	Nucleoside metabolic inhibitor	396	0.8%
Rituximab	CD20-directed cytolytic antibody	371	0.2%
Mycophenolate mofetil	Antimetabolite immunosuppressant	365	0.4%
Cefepime	Cephalosporin antibacterial	361	6.7%
Gabapentin	Anti-epileptic agent	332	0.4%
Methylprednisolone	Corticosteroid	330	0.7%
Carboplatin	Platinum-based drug	321	0.3%
Valproic acid	Anti-epileptic agent	290	1.4%
Metformin	Biguanide	288	0.4%
Lamotrigine	Anti-epileptic agent	282	0.6%
Vincristine	—	265	0.4%
Clonazepam	Benzodiazepine	260	0.7%
Fluorouracil	Nucleoside metabolic inhibitor	255	0.4%
Quetiapine	Atypical antipsychotic	253	0.5%

Drugs with a page on this site, ordered by the number of their reports recording this term. The last column is the term's share within that drug's own reports, against 0.1% across the whole database. 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."

By pharmacologic class

Class	Reports with this term	Share of class reports	Median drug in class
Corticosteroid	1,888	0.2%	0%
Anti-epileptic agent	1,725	0.6%	0.7%
Alkylating drug	1,495	0.6%	0.2%
Benzodiazepine	1,451	0.6%	0.5%
Nucleoside metabolic inhibitor	1,216	0.4%	0.1%
Atypical antipsychotic	1,177	0.2%	0%
Opioid agonist	1,156	0.1%	0%
Folate analog metabolic inhibitor	1,068	0.3%	0.1%
Nonsteroidal anti-inflammatory drug	1,029	0.2%	0%
Calcineurin inhibitor immunosuppressant	1,020	0.5%	0.4%

Classes ordered by count. Class shares follow the class's overall report volume as much as anything else.

Patients in these reports

Patient age

Under 21.3%305

2 to 114.1%991

12 to 173.5%855

18 to 4414.7%3,548

45 to 6425%6,028

65 to 7416.4%3,961

75 and over13.6%3,271

Age not given21.3%5,132

Patient sex

Female44.8%10,784

Male43.1%10,372

Not given12.2%2,935

Grey bar: all 20,646,523 reports in the database. 46.5% of these reports give the United States as the country.

Questions about "Encephalopathy"

What does "Encephalopathy" mean in an adverse event report?

It is a MedDRA preferred term, the dictionary FDA uses to code what a reporter described. The report's own description is not published by openFDA and is not shown here.

How many reports record encephalopathy?

24,091 reports through June 2026 (0.1% of all reports), 1,655 of them in the latest 12 months.

Which drugs appear most often in these reports?

Baclofen (911), Methotrexate (890), Tacrolimus (647), Prednisone (630) and Cyclophosphamide (626). Drugs with many reports overall lead almost every term's list. 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."

Does a drug appearing here mean it was responsible for this reaction?

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."

I have this symptom. What should I do?

This site cannot assess anyone. A pharmacist or clinician can; for an emergency, call the local emergency number. Nothing on this page is medical advice.

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. Terms are pooled across spelling and capitalisation variants of one MedDRA preferred term. 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.