What the label lists and what reports show
Dofetilide side effects
Dofetilide's FDA label lists its adverse reactions in its own words. FAERS holds 10,448 reports naming it through July 30, 2026; the reaction reported most often, leaving out the conditions it is used for, product-use terms and outcomes, is dyspnoea (613 reports).
- Generic listed
- Boxed warning
Check it at the source: the dofetilide FDA label on DailyMed (effective April 21, 2026, Pfizer Laboratories Div Pfizer Inc); the FDA FAERS public dashboard.
What does the patient leaflet say about side effects?
From the patient leaflet: What are the possible side effects of TIKOSYN?TIKOSYN can cause serious side effects, including a type of abnormal heartbeat called Torsade de Pointes, which can lead to death. See "What is the most important information I should know about TIKOSYN?" The most common side effects of TIKOSYN include: • headache • chest pain • dizziness Call your doctor right away if you have signs of electrolyte imbalance: • severe diarrhea • unusual sweating • vomiting • not hungry (loss of appetite) • increased thirst (drinking more than normal) Tell your doctor if you have any side effects that bother you or do not go away. These are not all the possible side effects of TIKOSYN. For more information, ask your doctor or pharmacist. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.
Source: FDA drug label, Pfizer Laboratories Div Pfizer Inc, effective April 21, 2026 (SPL set 02438044-d6a3-49e9-a1ac-3aad21ef2c8c), via openFDA; the full label on DailyMed
What does the label list?
From the label: adverse reactionsThe TIKOSYN clinical program involved approximately 8,600 patients in 130 clinical studies of normal volunteers and patients with supraventricular and ventricular arrhythmias. TIKOSYN was administered to 5,194 patients, including two large, placebo-controlled mortality trials (DIAMOND CHF and DIAMOND MI) in which 1,511 patients received TIKOSYN for up to three years. In the following section, adverse reaction data for cardiac arrhythmias and non-cardiac adverse reactions are presented separately for patients included in the supraventricular arrhythmia development program and for patients included in the DIAMOND CHF and MI mortality trials (see CLINICAL STUDIES, Safety in Patients with Structural Heart Disease, DIAMOND Studies, for a description of these trials). …
Table 8: Frequency of Adverse Events Occurring at >2% on TIKOSYN, and Numerically More Frequently on TIKOSYN than Placebo in Patients with Supraventricular Arrhythmias
| Adverse Event | TIKOSYN % | Placebo % |
|---|---|---|
| headache | 11 | 9 |
| chest pain | 10 | 7 |
| dizziness | 8 | 6 |
| respiratory tract infection | 7 | 5 |
| dyspnea | 6 | 5 |
| nausea | 5 | 4 |
| flu syndrome | 4 | 2 |
| insomnia | 4 | 3 |
| accidental injury | 3 | 1 |
| back pain | 3 | 2 |
| procedure (medical/surgical/health service) | 3 | 2 |
| diarrhea | 3 | 2 |
| rash | 3 | 2 |
| abdominal pain | 3 | 2 |
Rows and numbers as the label prints them, under its own column headings (the first rows of a longer table where it runs on). A reaction in a trial table is not necessarily caused by the medicine, and trials differ from everyday use.
Source: FDA drug label, Pfizer Laboratories Div Pfizer Inc, effective April 21, 2026 (SPL set 02438044-d6a3-49e9-a1ac-3aad21ef2c8c), via openFDA; the full label on DailyMed
What do FAERS reports show?
10,448 reports list dofetilide among the medicines taken, each a report of something that happened, not proof the medicine caused it; 811 are coded as a death and 2,996 as a hospital stay. Counts follow how widely a medicine is used and watched, and they are not a measure of how risky it is. Of the 18 reactions below, 8 are named by the same term (in US spelling) in the label's adverse reactions, warnings or patient leaflet; a reaction the label does not name may still be there under another word, and a report does not show that the medicine caused it.
Reports received each year
The 25 most reported reactions
Source: FDA Adverse Event Reporting System (FAERS) via openFDA, reports through July 30, 2026; reactions as MedDRA preferred terms
What next?
- Dofetilide: the full record
- label, generics, price, shortages, recalls
- Report a side effect to the FDA
- MedWatch
- Side effects hub
- the most reported medicines and reactions