Dofetilide: what it treats, how to take it, side effects
Last updated September 3, 2026.
Dofetilide is an antiarrhythmic - it steadies an overactive, irregular heart rhythm. You may know it as Tikosyn. One of the few drugs in the world that begins in a hospital: the first days need monitored ground.
What does it treat?
Irregular heartbeat - including atrial fibrillation and atrial flutter.
How do you take it?
Exactly as directed, same times daily - but the start is special: at least 3 days in a hospital or a closely monitored setting when you begin or restart, because the drug can itself provoke an irregular rhythm while the dose is found. Read the patient information every time therapy begins. Kidney function sets the dose - the labs are the schedule. Never stop without your doctor; restarts go back through the monitored door. Missed dose: take it when you remember unless the next one is close; never double up.
Side effects to know
- Common: headache, chest pain, shortness of breath, nausea, flu-like symptoms, stomach pain, back pain, and trouble sleeping.
- Serious - call your doctor immediately: fast, pounding, or irregular heartbeat; rash; severe diarrhea; dizziness or fainting.
Who should not take it?
The interaction list is a gate, not a formality: many common drugs - certain antibiotics, antifungals, stomach and heart medications - push the level into the danger zone: every new product gets checked, and the written medication list you carry is part of the treatment. Kidney disease changes the dose. Severe diarrhea shifts the electrolytes the drug reads - a call, not a wait. If you become pregnant, call your doctor.
When is it an emergency?
Fainting, a racing or chaotic heartbeat, or chest pain is a 911 call. For an overdose, call Poison Control at 1-800-222-1222. Pymander's escalation routing is built and tested specifically for this class of decision; see the safety architecture working paper.
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Common questions
Why did this drug start in a hospital?
Because the drug that steadies rhythm can also provoke it: dofetilide can cause the heart to beat irregularly, and the risk is highest while the right dose is being found - so at least 3 days of close monitoring at every start and restart. The hospital days are the safety design, not a sign of severity. The patient information gets re-read at every start - that is on the label.
Why does everyone keep asking for my medication list?
The interaction gate: many common drugs - certain antibiotics, antifungals, stomach and heart medications - push dofetilide's level into the danger zone. The defense is mechanical: a written list of everything you take, carried, brought to every visit and admission, and every new product checked before the first dose. On this drug, the list is load-bearing.
Why the kidney labs?
The kidneys clear the drug: kidney function sets the dose, and changes in function move the level - so the labs run on a schedule, not on a hunch. Severe diarrhea matters for the same family of reasons: it swings the electrolytes the heart rhythm reads. That is why "just a stomach bug" earns a call on this drug.
What does the dizziness-or-fainting warning mean?
The rhythm speaking: dizziness or fainting on an antiarrhythmic can mean the drug is provoking the very irregularity it treats - a call-immediately signal, with the racing-or-pounding heartbeat and rash alongside it. Fainting is never a wait-and-see on this drug: sit or lie down first, then the emergency pathway.
Can I stop it if my rhythm has been quiet?
Quiet is the drug working - and stopping without the doctor invites the irregularity back, sometimes fast. Restarts after a gap go back through the monitored door: the 3-day rule applies again. Any pause, stop, or switch is the cardiologist's planned move, never a lapsed refill.
What happens if I miss a dose of dofetilide?
Take it as soon as you remember, unless it is almost time for the next one - then skip it and never double up: doubling swings the level exactly the wrong way. The same-times-daily anchors keep the rhythm steady. Missed several doses? Call before restarting - the monitored-restart rule may apply.