Act now: Australia – Poisons Information Centre 13 11 26 (24 hours). US – Poison Control 1-800-222-1222. UK – NHS 111. Call your emergency number (000, 911, 999/112) straight away if there is chest pain, a racing, very slow or irregular pulse, fainting, breathlessness or a seizure.
The short answer
- Flecainide: a double dose needs professional advice immediately, because toxicity can develop over several hours.
- Have ready: the pack (strength), how many tablets, the time taken, your weight, your other medicines and your heart condition.
- Don’t take your next dose until you’ve been told it’s safe, and don’t try to make yourself vomit.
Why a double dose of flecainide is different
Flecainide (Tambocor, Flecainide acetate, also modified-release capsules) is an anti-arrhythmic used for atrial fibrillation and some other rhythm problems. It works by slowing electrical conduction in the heart. The gap between an effective dose and a toxic one is narrow, and too much can widen the QRS complex on the ECG, slow conduction further, cause dangerous fast or slow rhythms and lower blood pressure. People with heart failure, kidney impairment or older age clear it more slowly, which increases risk.
Not every double dose causes problems: someone who took an extra 50 mg tablet may well be fine. But the decision needs someone who can weigh your dose, timing and heart history, and you may be asked to attend hospital for an ECG and monitoring.
Symptoms of too much flecainide
- Dizziness, light-headedness, fainting
- Blurred or double vision
- Palpitations, a very fast, very slow or irregular pulse
- Nausea, vomiting
- Breathlessness, chest pain
- Tremor or, rarely, seizures
Symptoms can appear within a few hours, and modified-release forms can delay them. Not having symptoms yet doesn’t mean you’re in the clear.
A plan for any double dose
- Stop and check: what was taken, what strength, how many, and when.
- Check if it’s a high-risk medicine (table below). If yes, call for advice now.
- If it’s a lower-risk medicine, read the leaflet’s “if you take more than you should” section; many say skip the next dose.
- Don’t drive yourself to hospital; ask someone to take you or call an ambulance.
- Prevent repeats: use a weekly pill organiser or blister packs from the pharmacy, and set reminders.
| Higher risk if doubled – get advice now |
Usually lower risk – check the leaflet |
| Heart rhythm medicines (flecainide, digoxin, sotalol, amiodarone) |
Most statins |
| Beta blockers, calcium channel blockers (verapamil, diltiazem) |
Most antibiotics |
| Insulin, sulfonylureas (gliclazide) |
Antihistamines (non-sedating) |
| Opioids, benzodiazepines |
Proton pump inhibitors |
| Lithium, tricyclic antidepressants |
Most SSRIs (single extra dose) |
| Warfarin, methotrexate (any extra dose) |
Vitamins (except iron in children) |
| Paracetamol on top of other paracetamol |
Levothyroxine (single extra dose) |
More on missed and double doses is in our guide to taking medicines correctly.
Frequently asked questions
What are the symptoms of too much flecainide?
Dizziness, blurred vision, nausea, palpitations, a slow or irregular pulse, fainting and breathlessness. Seek urgent care if any occur after an extra dose.
Should I skip my next flecainide dose after taking two?
Ask the poisons centre or your doctor; they will usually advise skipping or delaying it, depending on timing. Don’t decide on your own.
I missed a dose of flecainide. Should I double the next one?
No. Take the missed dose if you remember within a few hours, otherwise skip it and take the next one at the normal time.
Sources and further reading
CanforaMedicine Guide
