Sotalol

What sotalol does

Sotalol is unusual because it has two separate actions. First, it is a non-selective beta-blocker — it slows the heart rate and reduces adrenaline effects on the heart. Second, and more importantly for rhythm control, it blocks a potassium channel called IKr, which prolongs the time it takes for heart cells to reset between beats. This second action is what we call a Class III effect, and it is shared with drugs like amiodarone and dofetilide.

Lengthening the reset (repolarization) makes it harder for AF or VT to sustain. The trade-off is that the same lengthening shows up on the ECG as a longer QT interval, and a QT that gets too long can trigger a specific dangerous rhythm called torsades de pointes. Everything we do with sotalol — in-hospital initiation, dose by kidney function, drug avoidance — is built around keeping the QT in a safe range.

Who we prescribe it for

We use sotalol in three main settings:

• Atrial fibrillation and atrial flutter — to maintain normal rhythm in patients who have had cardioversion or whose episodes we want to prevent. Unlike flecainide and propafenone, sotalol is acceptable in patients with coronary artery disease.
• Ventricular tachycardia — particularly in patients with an ICD, where reducing the frequency of VT episodes reduces shocks.
• Some inherited or acquired arrhythmias when other options are limited.

We do not use sotalol in patients with significant baseline QT prolongation, severe heart failure, very slow heart rates, or advanced AV block without a pacemaker.

How we start it — the hospital admission

Almost all patients start sotalol in the hospital on a continuous cardiac monitor. The reason is simple: the riskiest window for torsades is during the first few doses, when blood levels are rising and the QT is changing.

A typical admission looks like this:

• Baseline ECG and electrolytes (potassium and magnesium need to be normal).
• First dose given.
• ECGs checked at intervals through each dose change.
• We increase the dose every 12 hours or so if the QT stays within a safe range.
• Once we reach the target dose and the QT is acceptable, we send you home — usually after about three days.

This protocol is not optional. Outpatient initiation has caused deaths and is no longer standard.

Dosing and kidney function

Sotalol is cleared by the kidneys, so the dose depends on your creatinine clearance. Roughly:

• Normal kidney function: 80–160 mg twice daily.
• Moderately reduced: 80 mg once daily.
• Significantly reduced: lower still, or we choose a different drug.

If your kidney function changes — from dehydration, a new medication, or contrast for a scan — the sotalol level can climb. We re-check kidney function at follow-up and any time there is a meaningful change in health.

Side effects to watch for

Most patients tolerate sotalol reasonably well. Common things:

• Fatigue, slower exercise tolerance — from the beta-blocker effect.
• Dizziness or light-headedness, particularly when standing.
• Cold hands and feet.
• Slow heart rate (bradycardia).
• Shortness of breath in patients with asthma or COPD — sotalol’s non-selective beta-blockade can worsen wheezing.

The serious concern is torsades de pointes — a rhythm that can cause fainting or cardiac arrest. Warning signs we want you to call about immediately: fainting, near-fainting, palpitations that feel different from your usual rhythm, or a very slow pulse.

Drug and electrolyte interactions

Anything that further prolongs the QT or lowers potassium or magnesium raises risk. The list to avoid or be cautious with includes:

• Certain antibiotics (azithromycin, clarithromycin, levofloxacin, moxifloxacin).
• Antifungals (fluconazole, ketoconazole).
• Some antidepressants (citalopram at higher doses, escitalopram, tricyclics).
• Antipsychotics (haloperidol, ziprasidone, others).
• Ondansetron at higher doses.
• Methadone.
• Diuretics that lower potassium without replacement.

Always tell new prescribers — especially urgent care and dentists — that you are on sotalol.

Monitoring

After hospital discharge we check an ECG at follow-up to confirm the QT remains stable. We typically check kidney function and electrolytes at the same time. If you start a new medication that could interact, we may want an additional ECG.

When to call us

Call urgently for fainting, near-fainting, prolonged palpitations, new shortness of breath, or a pulse under 50 with symptoms. Tell us about any new prescription before you start it.