Drugs for Arrhythmias

• Supraventricualr arrhythmias:

ADENOSINE:

Indications: Conversion to sinus rhythm of paroxysmal supraventricular tachycardia (PSVT), including that associated with accessory bypass tracts (Wolff-Parkinson-White Syndrome). When clinically advisable, appropriate vagal maneuvers (e.g., Valsalva maneuver), should be attempted prior to Adenosine administration

Contraindications: Adenosine injection is contraindicated in:

Second- or third-degree A-V block (except in patients with a functioning artificial pacemaker. Sinus node disease, such as sick sinus syndrome or symptomatic bradycardia (except in patients with a functioning artificial pacemaker). Known hypersensitivity to Adenosine.

Dosage and Administration: Adenosine injection should be given as a rapid bolus by the peripheral intravenous route. The recommended intravenous doses for adults are as follows; Initial dose: 6 mg given as a rapid intravenous bolus (administered over a 1-2 second period). Repeat administration: If the first dose does not result in elimination of the supraventricular tachycardia within 1-2 minutes, 12 mg should be given as a rapid intravenous bolus. This 12 mg dose may be repeated a second time if required. Pediatric Patients with a Body Weight < 50 kg: Initial dose: Give 0.05 to 0.1 mg/kg as a rapid IV bolus given either centrally or peripherally. A saline flush should follow. Repeat administration: If conversion of PSVT does not occur within 1-2 minutes, additional bolus injections of Adenosine can be administered at incrementally higher doses, increasing the amount given by 0.05 to 0.1 mg/kg. Follow each bolus with a saline flush. This process should continue until sinus rhythm is established or a maximum single dose of 0.3 mg/kg is used. Pediatric Patients with a Body Weight ≥ 50 kg: Administer the adult dose. Doses greater than 12 mg are not recommended for adult and pediatric patients.

VERAPAMIL:

Indications: Verapamil is indicated for the treatment of Angina at rest including Vasospastic (Prinzmetal’s variant) angina, Unstable (crescendo, preinfarction) angina and chronic stable angina (classic effort-associated angina). Arrhythmias: In association with digitalis for the control of ventricular rate at rest and during stress in patients with chronic atrial flutter and/or atrial fibrillation and Prophylaxis of repetitive paroxysmal supraventricular tachycardia. Essential Hypertension.

Contraindications: Severe left ventricular dysfunction, Hypotension (systolic pressure less than 90 mm Hg) or cardiogenic shock, Sick sinus syndrome , Second- or third-degree AV block, Patients with atrial flutter or atrial fibrillation and an accessory bypass tract and Patients with known hypersensitivity to Verapamil hydrochloride.

Dosage and Administration: Angina: Clinical trials show that the usual dose is 80 mg to 120 mg three times a day. However, 40 mg three times a day may be warranted in patients who may have an increased response to Verapamil. Arrhythmias: The dosage in digitalized patients with chronic atrial fibrillation ranges from 240 to 320 mg/day in divided (t.i.d. or q.i.d.) doses. Essential hypertension: Dose should be individualized by titration. The usual initial monotherapy dose in clinical trials was 80 mg three times a day (240 mg/day).

Supraventricualr and Ventricular arrhythmias:

AMIDARONE:

Indications: Treating life-threatening recurrent heart rhythm disturbances in patients who cannot tolerate or do not respond well to other medicines. Recurrent ventricular fibrillation, Recurrent hemodynamically unstable ventricular tachycardia

Contraindications: Cordarone is contraindicated in patients with cardiogenic shock; severe sinus-node dysfunction, causing marked sinus bradycardia; second- or third-degree atrioventricular block; and when episodes of bradycardia have caused syncope (except when used in conjunction with a pacemaker).

Dosage and Administration: Because of the serious nature of the arrhythmia and the lack of predictable time course of effect, loading should be performed in a hospital setting. Loading doses of 800 to 1,600 mg/day are required for 1 to 3 weeks (occasionally longer) until initial therapeutic response occurs. (Administration of Cordarone in divided doses with meals is suggested for total daily doses of 1,000 mg or higher, or when gastrointestinal intolerance occurs.) If side effects become excessive, the dose should be reduced. Elimination of recurrence of ventricular fibrillation and tachycardia usually occurs within 1 to 3 weeks, along with reduction in complex and total ventricular ectopic beats. By I.V. infusion via central venous catheter, initially 5mg/kg over 20-120 minutes with ECG monitoring.

PROCAINAMIDE:

Indications: Treatment of documented ventricular arrhythmias, such as sustained ventricular tachycardia, that, in the judgment of the physician, are life threatening. Because of the proarrhythmic effects of Procainamide, its use with lesser arrhythmias is generally not recommended. Treatment of patients with asymptomatic ventricular premature contractions should be avoided.

Contraindications: Procainamide should not be administered to patients with complete heart block, In patients sensitive to procaine or other ester-type local anesthetics, systemic lupus erythematosus and In the unusual ventricular arrhythmia called “les torsades de pointes” (Twistings of the points).

Dosage and Administration: slow IV injection, rate not exceeding 50mg/min, 100mg with ECG monitoring, repeated at 5 min. intervals ( max 1g), IV infusion, 500-600mg over 30 min. with ECG monitoring followed by mainenance dose at rate of 2-6 mg/min.

Ventricular arrhythmias:

LIDOCAINE:

Indications: ventricular arrhythmias especially after myocardial infarction. Contraindications: sino_atrial disorders, AV block, sever myocardial depression, porphyria.

Dosage and Administration: by IV injection, 100mg as a bolus over few minutes followed immediately by ifusion of 4mg/min for 30 mins, 2mg/min for 2 hrs, then 1mg/min (ECG monitoring required)

PHENYTOIN:

Indications: ventricular arrhythmias.

Contraindications: sinus bradycardia, sino-atrial block, and second- and third-degree heart block; Stokes-Adams syndrome; acute porphyria

Dosage and Administration:IV injection via caval catheter, 3.5_ 5 mg/kg. Rate not > 50mg/min with BP and ECG monitoring. May repeat once if necessary.