PlainMeds research, FDA and CMS files of October 8, 2026
The medicines other labels name most
Phenytoin is named in the interaction, contraindication or boxed-warning sections of 290 other medicines' FDA labels, more than any other.
What the data shows
| Medicine | Labels naming it |
|---|---|
| Phenytoin | 290 |
| Rifampin | 267 |
| Warfarin | 254 |
| Ketoconazole | 242 |
| Carbamazepine | 217 |
| Digoxin | 206 |
| Cyclosporine | 190 |
| Ritonavir | 183 |
| Itraconazole | 169 |
| Lithium | 150 |
| Phenobarbital | 150 |
| Erythromycin | 136 |
| Clarithromycin | 133 |
| Cimetidine | 121 |
| Quinidine | 119 |
| Methotrexate | 103 |
| Theophylline | 100 |
| Tacrolimus | 98 |
| Fluconazole | 91 |
| Verapamil | 89 |
| Midazolam | 85 |
| Voriconazole | 83 |
| Diltiazem | 82 |
| Aspirin | 80 |
| Fluoxetine | 79 |
| Nelfinavir | 79 |
| Simvastatin | 79 |
| Rifabutin | 78 |
| Amiodarone | 77 |
| Atazanavir | 75 |
| Atorvastatin | 74 |
| Paroxetine | 69 |
| Methadone | 68 |
| Omeprazole | 66 |
| Epinephrine | 65 |
| Linezolid | 65 |
| Probenecid | 63 |
| Efavirenz | 62 |
| Methylene blue | 58 |
| Propranolol | 57 |
Source: FDA drug labels (Structured Product Labeling) via openFDA, read October 8, 2026
How it was measured
Every sentence of the FDA labels quoted on this site, in those three sections, matched against the medicine names and brand names on the site; a label counts once per medicine it names.
What it cannot show
A label names what its studies and reports found and the classes it warns about; a medicine named by many labels is widely studied with others, not necessarily riskier.