Sotalol (Sotalol Hydrochloride) - Drug Interactions, Contraindications, Overdosage

DRUG INTERACTIONS

Drugs undergoing CYP450 metabolism

Sotalol is primarily eliminated by renal excretion; therefore, drugs that are metabolized by CYP450 are not expected to alter the pharmacokinetics of sotalol. Sotalol is not expected to inhibit or induce any CYP450 enzymes; therefore, it is not expected to alter the PK of drugs that are metabolized by these enzymes.

Antiarrhythmics

Class Ia antiarrhythmic drugs, such as disopyramide, quinidine and procainamide and other Class III drugs (e.g., amiodarone) are not recommended as concomitant therapy with sotalol, because of their potential to prolong refractoriness (see WARNINGS). There is only limited experience with the concomitant use of Class Ib or Ic antiarrhythmics. Additive Class II effects would also be anticipated with the use of other beta-blocking agents concomitantly with sotalol.

Digoxin

Single and multiple doses of sotalol do not substantially affect serum digoxin levels. Proarrhythmic events were more common in sotalol treated patients also receiving digoxin; it is not clear whether this represents an interaction or is related to the presence of CHF, a known risk factor for proarrhythmia, in the patients receiving digoxin.

Calcium blocking drugs

Sotalol should be administered with caution in conjunction with calcium blocking drugs because of possible additive effects on atrioventricular conduction or ventricular function. Additionally, concomitant use of these drugs may have additive effects on blood pressure, possibly leading to hypotension.

Catecholamine-depleting agents

Concomitant use of catecholamine-depleting drugs, such as reserpine and guanethidine, with a beta-blocker may produce an excessive reduction of resting sympathetic nervous tone. Patients treated with sotalol plus a catecholamine depletor should therefore be closely monitored for evidence of hypotension and or marked bradycardia which may produce syncope.

Insulin and oral antidiabetics

Hyperglycemia may occur, and the dosage of insulin or antidiabetic drugs may require adjustment. Symptoms of hypoglycemia may be masked.

Beta-2-receptor stimulants

Beta-agonists such as salbutamol, terbutaline and isoprenaline may have to be administered in increased dosages when used concomitantly with sotalol.

Clonidine

Beta-blocking drugs may potentiate the rebound hypertension sometimes observed after discontinuation of clonidine; therefore, caution is advised when discontinuing clonidine in patients receiving sotalol.

Other

No pharmacokinetic interactions were observed with hydrochlorothiazide or warfarin.

Antacids

Administration of sotalol within 2 hours of antacids containing aluminum oxide and magnesium hydroxide should be avoided because it may result in a reduction in C_max and AUC of 26% and 20%, respectively and consequently in a 25% reduction in the bradycardic effect at rest. Administration of the antacid two hours after sotalol has no effect on the pharmacokinetics or pharmacodynamics of sotalol.

Drugs prolonging the QT interval

Sotalol should be administered with caution in conjunction with other drugs known to prolong the QT interval such as Class I and Class III antiarrhythmic agents, phenothiazines, tricyclic antidepressants, astemizole, bepridil, certain oral macrolides, and certain quinolone antibiotics (see WARNINGS).

OVERDOSAGE

Intentional or accidental overdosage with sotalol has rarely resulted in death.

Symptoms and Treatment of Overdosage

The most common signs to be expected are bradycardia, congestive heart failure, hypotension, bronchospasm and hypoglycemia. In cases of massive intentional overdosage (2-16 grams) of sotalol the following clinical findings were seen: hypotension, bradycardia, cardiac asystole, prolongation of QT interval, torsade de pointes, ventricular tachycardia, and premature ventricular complexes. If overdosage occurs, therapy with sotalol should be discontinued and the patient observed closely. Because of the lack of protein binding, hemodialysis is useful for reducing sotalol plasma concentrations. Patients should be carefully observed until QT intervals are normalized and the heart rate returns to levels >50 bpm. The occurrence of hypotension following an overdose may be associated with an initial slow drug elimination phase (half life of 30 hours) thought to be due to a temporary reduction of renal function caused by hypotension. In addition, if required, the following therapeutic measures are suggested:

Bradycardia or Cardiac Asystole:	Atropine, another anticholinergic drug, a beta-adrenergic agonist or transvenous cardiac pacing.
Heart Block:	(second and third degree) transvenous cardiac pacemaker.
Hypotension:	(depending on associated factors) epinephrine rather than isoproterenol or norepinephrine may be useful.
Bronchospasm:	Aminophylline or aerosol beta-2-receptor stimulant.
Torsade de pointes:	DC cardioversion, transvenous cardiac pacing, epinephrine, magnesium sulfate.

CONTRAINDICATIONS

Sotalol is contraindicated in patients with bronchial asthma, sinus bradycardia, second and third degree AV block, unless a functioning pacemaker is present, congenital or acquired long QT syndromes, cardiogenic shock, uncontrolled heart failure, and previous evidence of hypersensitivity to sotalol.