MedDRA preferred term
Drug effect less than expected: adverse event reports recording this term
13,914 reports to FDA record it, 2015–2026; 0.1% of the database.
- 13,914
- reports recording the term
- 0.1% of all reports
- 3,336
- reports, 12 months to June 2026
- 2,888 in the 12 months before
- 25.2%
- 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 less than expected" is a MedDRA preferred term recorded in 13,914 adverse event reports received by FDA, 0.1% of the database, from March 2015 to June 2026. The term is chosen by whoever codes the report to match what the reporter described.
3,336 reports recorded it in the 12 months to June 2026, up 16% from 2,888 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, 25.2% are marked serious, 0.9% include death among the outcomes and 7.3% include hospitalisation, as reported.
The drugs listed most often as suspect products in those reports are Dupixent, Vedolizumab and Jeuveau. 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 |
|---|---|---|---|
| Dupixent | Interleukin-4 receptor alpha antagonist | 1,408 | 0.3% |
| Vedolizumab | Integrin receptor antagonist | 509 | 0.9% |
| Jeuveau | Acetylcholine release inhibitor | 469 | 12.5% |
| Voltaren Arthritis Pain | — | 392 | 2.2% |
| Vyepti | — | 358 | 4% |
| Diclofenac sodium | Nonsteroidal anti-inflammatory drug | 321 | 0.6% |
| Kesimpta | CD20-directed cytolytic antibody | 318 | 1.1% |
| Gemtesa | beta3-Adrenergic agonist | 227 | 3.9% |
| Xeljanz | Janus kinase inhibitor | 213 | 0.1% |
| Cosentyx | Interleukin-17A antagonist | 201 | 0.1% |
| Wegovy | GLP-1 receptor agonist | 150 | 0.8% |
| Otezla | Phosphodiesterase 4 inhibitor | 140 | 0.1% |
| Xywav | Central nervous system depressant | 124 | 1.5% |
| Advil | Nonsteroidal anti-inflammatory drug | 117 | 0.6% |
| Advil Dual Action with Acetaminophen | Nonsteroidal anti-inflammatory drug | 117 | 5.4% |
| Inbrija | Aromatic amino acid | 107 | 1.8% |
| Repatha | PCSK9 inhibitor | 102 | 0.1% |
| Vyvanse | Central nervous system stimulant | 99 | 0.6% |
| Polyethylene glycol 3350 | Osmotic laxative | 97 | 1.7% |
| Adderall | Central nervous system stimulant | 95 | 0.9% |
| Heparin sodium | Anti-coagulant | 92 | 0.7% |
| Trelegy Ellipta | Anticholinergic | 85 | 0.3% |
| Excedrin Migraine | Central nervous system stimulant | 81 | 1.7% |
| Ozempic | GLP-1 receptor agonist | 78 | 0.1% |
| Letybo | Acetylcholine release inhibitor | 77 | 30.6% |
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 |
|---|---|---|---|
| Interleukin-4 receptor alpha antagonist | 1,431 | 0.3% | 0.3% |
| Nonsteroidal anti-inflammatory drug | 888 | 0.2% | 0% |
| Integrin receptor antagonist | 573 | 0.2% | 0.2% |
| Central nervous system stimulant | 551 | 0.5% | 0.2% |
| Acetylcholine release inhibitor | 503 | 0.6% | 0% |
| CD20-directed cytolytic antibody | 401 | 0.1% | 0% |
| Atypical antipsychotic | 347 | 0.1% | 0% |
| GLP-1 receptor agonist | 337 | 0.1% | 0.1% |
| Tumor necrosis factor blocker | 334 | 0% | 0% |
| Janus kinase inhibitor | 316 | 0.1% | 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
Patient sex
Grey bar: all 20,646,523 reports in the database. 86.5% of these reports give the United States as the country.
Questions about "Drug effect less than expected"
What does "Drug effect less than expected" 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 drug effect less than expected?
13,914 reports through June 2026 (0.1% of all reports), 3,336 of them in the latest 12 months.
Which drugs appear most often in these reports?
Dupixent (1,408), Vedolizumab (509), Jeuveau (469), Voltaren Arthritis Pain (392) and Vyepti (358). 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.