A boxed warning is the most serious warning the FDA requires on a prescription label. These pages report what the warning actually says for 67 commonly prescribed drugs, quoted from a specific identified label and linked back to it.
What these pages cover
They also record something less widely known: the wording is written by each manufacturer within the FDA's requirements, so it varies between labels for the same drug. Each page states how many distinct wordings were found and which one it is quoting.
| Drug | Warning concerns | FDA labels |
|---|---|---|
| Levothyroxine | not for treatment of obesity or for weight loss | 277 |
| Metformin | lactic acidosis | 253 |
| Bupropion | suicidal thoughts and behaviors suicidality and antidepressant drugs | 244 |
| Ibuprofen | cardiovascular thrombotic events | 229 |
| Lisinopril | fetal toxicity | 160 |
| Sertraline | suicidal thoughts and behaviors | 137 |
| Celecoxib | risk of serious cardiovascular and gastro-intestinal events... | 137 |
| Estradiol | estrogens increase the risk of endometrial cancer | 129 |
| Divalproex | life threatening adverse reactions hepatotoxicity general population | 127 |
| Ketorolac | ketorolac tromethamine, a nonsteroidal anti-inflammatory drug... | 117 |
| Metronidazole | metronidazole has been shown to be carcinogenic in mice and rats... | 106 |
| Olanzapine | increased mortality in elderly patients with dementia-related... | 103 |
| Zolpidem | complex sleep behaviour | 103 |
| Lamotrigine | serious skin rashes | 102 |
| Lorazepam | risks from concomitant use with opioids; abuse, misuse, and... | 98 |
| Carbamazepine | serious dermatologic reactions and hla-b*1502 allele serious and... | 91 |
| Clindamycin | clostridioides difficile -associated diarrhea (cdad) has been... | 78 |
| Methylphenidate | abuse, misuse, and addiction | 77 |
| Levofloxacin | serious adverse reactions including tendinitis, tendon rupture,... | 73 |
| Morphine Sulfate | addiction, abuse, and misuse; risk evaluation and mitigation... | 73 |
| Bumetanide | bumetanide is a potent diuretic which, if given in excessive... | 73 |
| Promethazine | promethazine hydrochloride tablets, usp should not be used in... | 59 |
| Lithium | lithium toxicity | 52 |
| Warfarin | bleeding risk | 47 |
| Clopidogrel Bisulfate | diminished antiplatelet effect in patients with two... | 42 |
| Tacrolimus | malignancies and serious infections | 42 |
| Methotrexate | embryo-fetal toxicity, hypersensitivity reactions, and severe... | 39 |
| Montelukast | serious neuropsychiatric events | 38 |
| Medroxyprogesterone Acetate | cardiovascular disorders, breast cancer and probable dementia for... | 35 |
| Amiodarone | pulmonary, hepatic and cardiac toxicity | 28 |
| Enoxaparin | spinal/epidural hematomas | 28 |
| Doxorubicin | cardiomyopathy and infusion-related reactions | 28 |
| Rivaroxaban | premature discontinuation of xarelto increases the risk of... | 26 |
| Leflunomide | embryo-fetal toxicity and hepatotoxicity embryo-fetal toxicity | 25 |
| Isotretinoin | embryo-fetal toxicity, contraindicated in pregnancy | 19 |
| Misoprostol | misoprostol administration to women who are pregnant can cause... | 19 |
| Azathioprine | malignancy chronic immunosuppression with azathioprine, a purine... | 18 |
| Liraglutide | risk of thyroid c-cell tumors | 18 |
| Lamivudine | exacerbations of hepatitis b, and different formulations of... | 18 |
| Clozapine | severe neutropenia; orthostatic hypotension, bradycardia, and... | 16 |
| Irinotecan | diarrhea and myelosuppression • early | 16 |
| Tamoxifen | for women with ductal carcinoma in situ (dcis) and | 14 |
| Metoclopramide | tardive dyskinesia | 13 |
| Gentamicin Sulfate | patients treated with aminoglycosides should be under close... | 12 |
| Ketoconazole | because ketoconazole tablets have been associated with serious... | 12 |
| Cisplatin | cisplatin should be administered under the supervision of a... | 12 |
| Pioglitazone | congestive heart failure | 11 |
| Cilostazol | contraindicated in heart failure patients | 11 |
| Cyclosporine | only physicians experienced in management of systemic... | 10 |
| Nevirapine | life-threatening (including fatal) hepatotoxicity and skin... | 9 |
| Propylthiouracil | severe liver injury and acute liver failure, in some cases fatal,... | 8 |
| Amikacin Sulfate | patients treated with parenteral aminoglycosides should be under... | 7 |
| Spironolactone | spironolactone has been shown to be a tumorigen in chronic toxicity... | 7 |
| Abacavir Sulfate | hypersensitivity reactions | 6 |
| Zidovudine | risk of hematological toxicity, myopathy, lactic acidosis and... | 6 |
| Thioridazine | thioridazine has been shown to prolong the qtc interval in a dose... | 5 |
| Mifepristone | termination of pregnancy | 5 |
| Fentanyl | serious and life-threatening risks from use of fentanyl transdermal... | 4 |
| Adalimumab | serious infections and malignancy serious infections | 4 |
| Dronedarone | increased risk of death, stroke and heart failure in patients with... | 2 |
| Vincristine Sulfate | caution, this preparation should be administered by individuals... | 2 |
| Epoetin Alfa | esas increase the risk of death, myocardial infarction, stroke,... | 1 |
| Salmeterol Xinafoate | asthma-related death | 1 |
| Chloramphenicol Sodium | serious and fatal blood dyscrasias (aplastic anemia, hypoplastic... | 1 |
| Natalizumab | progressive multifocal leukoencephalopathy | 1 |
| Ergotamine | serious and/or life-threatening peripheral ischemia has been... | 1 |
| Amphotericin B | this drug should be used primarily for treatment of patients with... | 1 |
Source: FDA product labelling via the openFDA API, retrieved 30 August 2026. Nothing on these pages is medical advice.