MedDRA preferred term · the medicine had less effect

Drug effect decreased: adverse event reports recording this term

53,762 reports to FDA record it, 2004–2019; 0.3% 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.

53,762
reports recording the term: 0.3% of all reports; 0
reports, 12 months to June 2026: 0 in the 12 months before; 29%
marked serious by the reporter: 57.4% across all reports; 0.9%
record death among outcomes, as reported: 9.1% across all reports

"Drug effect decreased" (in plain words, the medicine had less effect) is a MedDRA preferred term recorded in 53,762 adverse event reports received by FDA, 0.3% of the database, from January 2004 to March 2019. The term is chosen by whoever codes the report to match what the reporter described.

0 reports recorded it in the 12 months to June 2026, and none 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, 29% are marked serious, 0.9% include death among the outcomes and 8.2% include hospitalisation, as reported.

The drugs listed most often as suspect products in those reports are Enbrel, Humira and Butrans. 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
Enbrel	Tumor necrosis factor blocker	7,560	1.3%
Humira	—	5,497	0.9%
Butrans	Partial opioid agonist	1,659	2.8%
Byetta	GLP-1 receptor agonist	1,502	3.1%
Remicade	Tumor necrosis factor blocker	1,375	0.9%
Tysabri	Integrin receptor antagonist	1,316	0.8%
Methotrexate	Folate analog metabolic inhibitor	1,313	0.6%
OxyContin	Opioid agonist	1,216	0.8%
Fentanyl Transdermal System	—	1,106	8.7%
Vyvanse	Central nervous system stimulant	733	4.2%
Otezla	Phosphodiesterase 4 inhibitor	707	0.5%
Actemra	Interleukin-6 receptor antagonist	569	0.7%
Oxytrol for Women	Cholinergic muscarinic antagonist	557	8.9%
Simponi	Tumor necrosis factor blocker	549	0.8%
Orencia	Selective T cell costimulation modulator	544	0.5%
Viagra	Phosphodiesterase 5 inhibitor	498	1.8%
Claritin	—	480	2.5%
Lyrica	—	470	0.4%
Stelara	Interleukin-12 antagonist	465	0.5%
MiraLAX	Osmotic laxative	445	1.2%
Ampyra	Potassium channel blocker	433	0.8%
Xeljanz	Janus kinase inhibitor	426	0.3%
Plaquenil	Antimalarial	425	2%
Cosentyx	Interleukin-17A antagonist	416	0.3%
Rituxan	CD20-directed cytolytic antibody	368	0.9%

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 0.3% 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
Tumor necrosis factor blocker	10,061	0.9%	0.1%
Opioid agonist	2,960	0.3%	0.1%
Partial opioid agonist	1,699	1.8%	0%
Folate analog metabolic inhibitor	1,696	0.5%	0.2%
Central nervous system stimulant	1,607	1.5%	0.5%
GLP-1 receptor agonist	1,567	0.4%	0%
Integrin receptor antagonist	1,367	0.5%	0.1%
Corticosteroid	1,278	0.2%	0.1%
Atypical antipsychotic	1,132	0.2%	0.1%
Nonsteroidal anti-inflammatory drug	1,063	0.2%	0.1%

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 20.1%64

2 to 111.6%839

12 to 171.1%610

18 to 4412.2%6,579

45 to 6422.6%12,163

65 to 748.1%4,337

75 and over4.5%2,423

Age not given49.8%26,747

Patient sex

Female56%30,109

Male37%19,887

Not given7%3,766

Grey bar: all 20,646,523 reports in the database. 86.4% of these reports give the United States as the country.

Questions about "Drug effect decreased"

What does "Drug effect decreased" mean in an adverse event report?

In plain language: the medicine had less effect. 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 drug effect decreased?

53,762 reports through June 2026 (0.3% of all reports), 0 of them in the latest 12 months.

Which drugs appear most often in these reports?

Enbrel (7,560), Humira (5,497), Butrans (1,659), Byetta (1,502) and Remicade (1,375). 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.