MedDRA preferred term · an interaction between medicines
Drug interaction: adverse event reports recording this term
156,039 reports to FDA record it, 2004–2026; 0.8% of the database.
- 156,039
- reports recording the term
- 0.8% of all reports
- 8,141
- reports, 12 months to June 2026
- 7,917 in the 12 months before
- 88.9%
- marked serious by the reporter
- 57.4% across all reports
- 8.3%
- record death among outcomes, as reported
- 9.1% across all reports
"Drug interaction" (in plain words, an interaction between medicines) is a MedDRA preferred term recorded in 156,039 adverse event reports received by FDA, 0.8% of the database, from January 2004 to June 2026. The term is chosen by whoever codes the report to match what the reporter described.
8,141 reports recorded it in the 12 months to June 2026, close to the 7,917 of 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, 88.9% are marked serious, 8.3% include death among the outcomes and 45.3% include hospitalisation, as reported.
The drugs listed most often as suspect products in those reports are Tacrolimus, Quetiapine and Simvastatin. 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 |
|---|---|---|---|
| Tacrolimus | Calcineurin inhibitor immunosuppressant | 5,217 | 5.5% |
| Quetiapine | Atypical antipsychotic | 4,126 | 7.9% |
| Simvastatin | HMG-CoA reductase inhibitor | 3,928 | 11.1% |
| Omeprazole | Proton pump inhibitor | 3,776 | 6.2% |
| Methotrexate | Folate analog metabolic inhibitor | 3,348 | 1.6% |
| Furosemide | Loop diuretic | 3,327 | 6.8% |
| Sertraline | Serotonin reuptake inhibitor | 3,218 | 7.2% |
| Warfarin | Vitamin K antagonist | 3,188 | 13.6% |
| Valproic acid | Anti-epileptic agent | 3,126 | 14.8% |
| Fluoxetine | Serotonin reuptake inhibitor | 2,999 | 10.6% |
| Amlodipine | Calcium channel blocker | 2,918 | 5.6% |
| Clarithromycin | Macrolide antimicrobial | 2,812 | 12.9% |
| Atorvastatin | — | 2,777 | 6.2% |
| Olanzapine | Atypical antipsychotic | 2,713 | 5.8% |
| Risperidone | Atypical antipsychotic | 2,646 | 5.9% |
| Clonazepam | Benzodiazepine | 2,623 | 7% |
| Diazepam | Benzodiazepine | 2,582 | 6.4% |
| Clozapine | Atypical antipsychotic | 2,578 | 3.5% |
| Aspirin | Nonsteroidal anti-inflammatory drug | 2,541 | 3.5% |
| Lamotrigine | Anti-epileptic agent | 2,486 | 5.6% |
| Prednisone | Corticosteroid | 2,446 | 1.3% |
| Citalopram | Serotonin reuptake inhibitor | 2,396 | 7.9% |
| Acetaminophen | Nonsteroidal anti-inflammatory drug | 2,374 | 2.7% |
| Ciprofloxacin | Fluoroquinolone antibacterial | 2,363 | 6% |
| Fluconazole | Azole antifungal | 2,263 | 13.2% |
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 0.8% 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 |
|---|---|---|---|
| Atypical antipsychotic | 22,307 | 3.3% | 2% |
| Serotonin reuptake inhibitor | 19,472 | 7.1% | 7.9% |
| Anti-epileptic agent | 14,225 | 5.3% | 5% |
| Benzodiazepine | 12,652 | 5.2% | 5.3% |
| Nonsteroidal anti-inflammatory drug | 12,208 | 2.2% | 0.8% |
| Opioid agonist | 11,360 | 1.2% | 1.4% |
| HMG-CoA reductase inhibitor | 9,498 | 4.6% | 5.5% |
| Proton pump inhibitor | 9,211 | 1.9% | 0.8% |
| Corticosteroid | 8,866 | 1.1% | 0.4% |
| Serotonin and norepinephrine reuptake inhibitor | 7,738 | 4.5% | 4.2% |
Classes ordered by count. Class shares follow the class's overall report volume as much as anything else.
Patients in these reports
Patient age
Patient sex
Grey bar: all 20,646,523 reports in the database. 31.9% of these reports give the United States as the country.
Questions about "Drug interaction"
What does "Drug interaction" mean in an adverse event report?
In plain language: an interaction between medicines. 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 interaction?
156,039 reports through June 2026 (0.8% of all reports), 8,141 of them in the latest 12 months.
Which drugs appear most often in these reports?
Tacrolimus (5,217), Quetiapine (4,126), Simvastatin (3,928), Omeprazole (3,776) and Methotrexate (3,348). 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.