MedDRA preferred term

Myoclonus: adverse event reports recording this term

11,715 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.

11,715
reports recording the term: 0.1% of all reports; 576
reports, 12 months to June 2026: 637 in the 12 months before; 94.4%
marked serious by the reporter: 57.4% across all reports; 5.6%
record death among outcomes, as reported: 9.1% across all reports

"Myoclonus" is a MedDRA preferred term recorded in 11,715 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.

576 reports recorded it in the 12 months to June 2026, down 10% from 637 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, 94.4% are marked serious, 5.6% include death among the outcomes and 54.6% include hospitalisation, as reported.

The drugs listed most often as suspect products in those reports are Gabapentin, Levetiracetam and Lamotrigine. 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
Gabapentin	Anti-epileptic agent	917	1.2%
Levetiracetam	—	392	0.8%
Lamotrigine	Anti-epileptic agent	356	0.8%
Clozapine	Atypical antipsychotic	332	0.5%
Quetiapine	Atypical antipsychotic	317	0.6%
Sertraline	Serotonin reuptake inhibitor	314	0.7%
Pregabalin	—	286	0.8%
Lyrica	—	285	0.2%
Fentanyl	Opioid agonist	266	0.5%
Venlafaxine	Serotonin and norepinephrine reuptake inhibitor	250	0.8%
Tramadol	—	228	0.5%
Levofloxacin	Fluoroquinolone antibacterial	227	0.7%
Baclofen	gamma-Aminobutyric acid-ergic agonist	207	1%
Bupropion	Aminoketone	206	1%
Mirtazapine	—	206	0.6%
Fluoxetine	Serotonin reuptake inhibitor	201	0.7%
Olanzapine	Atypical antipsychotic	190	0.4%
Lorazepam	Benzodiazepine	188	0.6%
Morphine	Opioid agonist	187	0.7%
Morphine sulfate	Opioid agonist	179	0.3%
Ciprofloxacin	Fluoroquinolone antibacterial	172	0.4%
Propofol	General anesthetic	169	0.9%
Risperidone	Atypical antipsychotic	165	0.4%
Citalopram	Serotonin reuptake inhibitor	162	0.5%
Clonazepam	Benzodiazepine	156	0.4%

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
Anti-epileptic agent	1,779	0.7%	0.2%
Atypical antipsychotic	1,627	0.2%	0%
Serotonin reuptake inhibitor	1,378	0.5%	0.5%
Opioid agonist	1,342	0.1%	0%
Benzodiazepine	879	0.4%	0.3%
Serotonin and norepinephrine reuptake inhibitor	645	0.4%	0.2%
Mood stabilizer	413	0.7%	1%
Fluoroquinolone antibacterial	407	0.5%	0.1%
Corticosteroid	348	0%	0%
Aminoketone	331	0.5%	0.2%

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 22.7%314

2 to 112.7%320

12 to 173.3%381

18 to 4418.5%2,166

45 to 6424.8%2,906

65 to 7412.9%1,507

75 and over15.4%1,809

Age not given19.7%2,312

Patient sex

Female46.9%5,495

Male43.2%5,063

Not given9.9%1,157

Grey bar: all 20,646,523 reports in the database. 33.5% of these reports give the United States as the country.

Questions about "Myoclonus"

What does "Myoclonus" 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 myoclonus?

11,715 reports through June 2026 (0.1% of all reports), 576 of them in the latest 12 months.

Which drugs appear most often in these reports?

Gabapentin (917), Levetiracetam (392), Lamotrigine (356), Clozapine (332) and Quetiapine (317). 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.