On and off phenomenon adverse event reports that record this term

Kind of term: MedDRA preferred term

What a report is

A report is not proof that the drug was the cause of the event.

FDA says:

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.
Source: openFDA, Drug Adverse Event Overview, section "Responsible use of the data". The site read the page on 2 Oct 2026. The data have the reports that FDA received through 30 Jun 2026.

FDA also says:

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 has not been scientifically or otherwise verified as to a cause and effect relationship and cannot be used to estimate the incidence of these events.
Source: openFDA, Drug Adverse Event Overview. The site read the page on 2 Oct 2026.

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.
Source: openFDA, Response of the drug event API (meta.disclaimer). The site read the page on 2 Oct 2026.

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

Reports on file

From May 2005 to June 2026, FDA received 5,199 adverse event reports that record the MedDRA preferred term On and off phenomenon. The person who codes a report selects the term that agrees best with the description of the reporter.

FDA received 987 reports in the 12 months to June 2026 and 655 in the 12 months before. FDA releases FAERS data every quarter, so the newest months are not complete. They grow in later releases.

By reports in the 12 months to June 2026, this term was number 615 of 1,436 reaction terms with a page. Of the 1,332,454 drug reports that FDA received in the 12 months to June 2026, 987 (0.1%) record this term. Reports for male patients were 56.2% of the reports that record this term and 34.6% of all drug reports.

The number of people who use the product is not in the data. A count is not a rate.

MedDRA

The Medical Dictionary for Regulatory Activities. The person who codes a report selects the preferred term that agrees best with the description of the reporter. FDA does not publish the description.

Data version

openFDA FAERS release of 29 Oct 2026. Reports received through 30 Jun 2026.

Drugs in these reports

The table has the 94 drug pages with 5 or more reports that record this term. The rows are in order of name. A drug page with fewer reports for this term is not in the table. The counts are the counts that the site keeps for each reaction term, and a count can be lower than the count of FDA.

FDA says:

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.
Source: openFDA, Drug Adverse Event Overview. The site read the page on 2 Oct 2026.

Importantly, the AEMS data by themselves are not an indicator of the safety profile of the drug or biologic.
Source: FDA, FDA Adverse Event Monitoring System (AEMS) Public Dashboard. Content current as of 11 Mar 2026. The site read the page on 2 Oct 2026.

Drugs that the reports with the term On and off phenomenon name as a suspect product, in order of name
Drug	Class	Reports with this term
Acetaminophen		7
Alfuzosin		11
Amantadine	Influenza A M2 protein inhibitor	62
Amantadine hydrochloride	Influenza A M2 protein inhibitor	15
Amitriptyline		18
Amitriptyline hydrochloride	Tricyclic antidepressant	8
Apokyn	Dopaminergic agonist	67
Apomorphine		17
Apomorphine hydrochloride	Dopaminergic agonist	24
Atorvastatin		15
Azilect	Monoamine oxidase inhibitor	8
Benserazide Hydrochloride Levodopa		28
Benserazide Levodopa		12
Biperiden		7
Bisacodyl		17
Botox	Acetylcholine release inhibitor	17
Calcium carbonate	Blood coagulation factor	5
Caltrate with Vitamin D		14
Carbidopa		16
Carbidopa and levodopa	Aromatic amino acid	64
Carbidopa levodopa	Aromatic amino acid	2,084
Carbidopa-levodopa	Aromatic amino acid	7
Clonazepam	Benzodiazepine	12
Clopidogrel	P2Y12 platelet inhibitor	6
Clozapine	Atypical antipsychotic	88
Comtan		16
Crexont	Aromatic amino acid	8
Delorazepam		8
Domperidone		12
Domperidone maleate		7
Donepezil		5
Duodopa		1,187
Duopa	Aromatic amino acid	237
Dutasteride Tamsulosin Hydrochloride		14
Entacapone	Catechol-O-Methyltransferase inhibitor	58
Exelon	Cholinesterase inhibitor	5
Finasteride	5-alpha reductase inhibitor	12
Fludrocortisone		16
Foscarbidopa/foslevodopa		759
Furosemide	Loop diuretic	17
Gocovri	Influenza A M2 protein inhibitor	14
Hydrochlorothiazide	Thiazide diuretic	5
Hydroxyzine	Antihistamine	7
Ibuprofen	Nonsteroidal anti-inflammatory drug	5
Inbrija	Aromatic amino acid	72
Kynmobi		15
Lansoprazole	Proton pump inhibitor	6
Lasix	Loop diuretic	5
Levodopa	Aromatic amino acid	63
Levodopa/Carbidopa		15
Lorazepam	Benzodiazepine	10
Madopar		20
Metformin hydrochloride	Biguanide	14
Mirapexin		8
Mirtazapine		29
Neupro	Nonergot dopamine agonist	45
Nortriptyline hydrochloride	Tricyclic antidepressant	14
Nourianz		56
Nuplazid	Atypical antipsychotic	54
Olanzapine	Atypical antipsychotic	18
Omeprazole	Proton pump inhibitor	8
Onapgo	Dopaminergic agonist	13
Ongentys	Catechol-O-Methyltransferase inhibitor	21
Oxycodone	Opioid agonist	10
Paroxetine	Serotonin reuptake inhibitor	10
Polyethylene glycol 3350	Osmotic laxative	16
Polyethylene Glycols		8
Pradaxa	Direct thrombin inhibitor	6
Pramipexole	Nonergot dopamine agonist	99
Pramipexole dihydrochloride	Nonergot dopamine agonist	29
Prednisone	Corticosteroid	8
Pregabalin		23
Quetiapine	Atypical antipsychotic	43
Rabeprazole sodium	Proton pump inhibitor	14
Rasagiline	Monoamine oxidase inhibitor	25
Rasagiline mesylate	Monoamine oxidase inhibitor	18
Requip		12
Rivaroxaban	Factor Xa inhibitor	16
Rivastigmine	Cholinesterase inhibitor	55
Ropinirole	Nonergot dopamine agonist	59
Ropinirole hydrochloride	Nonergot dopamine agonist	10
Rotigotine	Nonergot dopamine agonist	16
Rytary	Aromatic amino acid	120
Selegiline	Monoamine oxidase inhibitor	12
Seroquel	Atypical antipsychotic	10
Sifrol		7
Sinemet	Aromatic amino acid	55
Solifenacin		6
Solifenacin succinate	Cholinergic muscarinic antagonist	14
Stalevo		27
Tenormin	beta-Adrenergic blocker	6
Vyalev		202
Xadago		11
Xarelto	Factor Xa inhibitor	17

The page of each drug has the count of each reaction term in its reaction lookup.

Drug classes in these reports

The table has the 28 pharmacologic classes with 5 or more reports that record this term. The rows are in order of name.

FDA says:

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.
Source: openFDA, Drug Adverse Event Overview. The site read the page on 2 Oct 2026.

Importantly, the AEMS data by themselves are not an indicator of the safety profile of the drug or biologic.
Source: FDA, FDA Adverse Event Monitoring System (AEMS) Public Dashboard. Content current as of 11 Mar 2026. The site read the page on 2 Oct 2026.

Pharmacologic classes of the drugs that the reports with the term On and off phenomenon name, in order of name
Class	Reports with this term
5-alpha reductase inhibitor	12
Acetylcholine release inhibitor	17
Antihistamine	7
Aromatic amino acid	2,695
Atypical antipsychotic	217
Benzodiazepine	32
beta-Adrenergic blocker	11
Biguanide	17
Blood coagulation factor	5
Catechol-O-Methyltransferase inhibitor	79
Cholinergic muscarinic antagonist	19
Cholinesterase inhibitor	60
Corticosteroid	10
Direct thrombin inhibitor	6
Dopaminergic agonist	104
Factor Xa inhibitor	36
Influenza A M2 protein inhibitor	91
Loop diuretic	22
Monoamine oxidase inhibitor	33
Nonergot dopamine agonist	258
Nonsteroidal anti-inflammatory drug	9
Opioid agonist	24
Osmotic laxative	18
P2Y12 platelet inhibitor	6
Proton pump inhibitor	31
Serotonin reuptake inhibitor	14
Thiazide diuretic	5
Tricyclic antidepressant	22

A class with many reports in all has many reports for almost every term.

Reports by month

Reports that record On and off phenomenon, by month, five years to June 2026

FDA releases FAERS data every quarter, so the newest months are not complete. They grow in later releases.

Patients in these reports

Age of the patient in the reports that record On and off phenomenon
Age	Reports	Share
Under 2	0	0%
2 to 11	2	under 0.1%
12 to 17	5	0.1%
18 to 44	53	1%
45 to 64	804	15.5%
65 to 74	1,538	29.6%
75 and over	1,207	23.2%
Age not given	1,590	30.6%

Sex of the patient in the reports that record On and off phenomenon
Sex	Reports	Share
Female	2,123	40.8%
Male	2,924	56.2%
Unknown or not given	152	2.9%

Age and sex are as the report gives them. 17.1% of these reports give the United States as the country.

Terms near this one

These are the next terms in the A to Z list. The links are for navigation.

Official pages

MedWatch Online Voluntary Reporting FormThe online form of FDA for a voluntary report.
MedWatch: The FDA Safety Information and Adverse Event Reporting ProgramThe page of the FDA program that receives reports about drugs and devices.
FDA Adverse Event Monitoring System (AEMS) Public DashboardThe public dashboard of FDA for adverse event reports on drugs and biologics.

The site checked these addresses on 2 Oct 2026. The links open in a new tab.

Cite this page

Reported Reactions. On and off phenomenon: adverse event reports that record this term. https://reportedreactions.com/reaction/on-and-off-phenomenon/ Source: U.S. Food and Drug Administration, openFDA Drug Adverse Event (FAERS) files, release of 29 Oct 2026. Reports received through 30 Jun 2026.

Where the data come from

The counts come from the openFDA Drug Adverse Event (FAERS) bulk files, release of 29 Oct 2026. The files have the reports that FDA received through 30 Jun 2026. A drug name is the name on the report. The site matches it to a brand name or a generic name of the National Drug Code Directory of 2 Nov 2026. A class is the pharmacologic class (EPC) of the FDA label.

The count has the reports with each spelling of one MedDRA preferred term. The site does not publish a report narrative, a lot number, a detail of a patient or the identity of a reporter. The record of FDA is the authority. See how the site counts reports, the data sources and the corrections page.

Questions

What does On and off phenomenon mean in an adverse event report?

It is a MedDRA preferred term. FDA codes the description of a reporter with the MedDRA dictionary. The openFDA files do not have the description itself, and this site does not show it.

Does a drug in the table mean that the drug was responsible for this reaction?

No. FDA says:

No individual drug is connected to any individual reaction.
Source: openFDA, Drug Adverse Event Overview. The site read the page on 2 Oct 2026.

When a report lists multiple drugs and multiple reactions, there is no way to conclude from the data therein that a given drug is responsible for a given reaction.
Source: openFDA, Drug Adverse Event Overview. The site read the page on 2 Oct 2026.

What does this page tell a person who has this symptom?

This page gives counts of reports. It cannot assess a person. A pharmacist or a clinician can assess a person.

If this is a medical emergency, please call 911.
Source: FDA, MedWatch Online Voluntary Reporting Form. The site read the page on 2 Oct 2026.

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