Tocainide (Tonocard) is an orally effective antiarrhyth-mic agent with close structural similarities to lidocaine.
In healthy volunteers, tocainide produced a slight de-pression in His-Purkinje conduction as well as a slightly delayed enhancement of A-V node conduction during atrial pacing. No significant alterations in heart rate, right ventricular ERP or the excitation thresholds of atrial or ventricular muscle were observed in these subjects.
The acute hemodynamic effects are slight and transient and are observed most often during or immediately af-ter drug infusion.
The pharmacokinetic characteristics of tocainide:
Oral bioavailability : Approximately 100%
Onset of action : Not known
Peak response : 0.5–2 hours
Duration of action : 8 hours
Plasma half-life : 15 hours
Primary route of metabolism: Hepatic
Primary route of excretion: Renal (40% unchanged)
Therapeutic serum : 3–11 : μg /mL concentration
Tocainide is indicated for the treatment of symptomatic ventricular arrhythmias refractory to more conventional therapy. Serious noncardiac adverse effects limit its use to patients with life-threatening arrhythmias.
Light-headedness, dizziness, or nausea occurs in ap-proximately 15% of patients, paresthesias and numb-ness in 9%, and tremor in 8%. These adverse effects are generally mild in intensity, transient, and dose related. Overall, however, approximately 20% of patients pre-scribed tocainide discontinue therapy because of such effects. Serious immune-based side effects, such as pul-monary fibrosis, have been reported, and blood dyscrasias, such as agranulocytosis and thrombocytope-nia, may occur in up to 0.2% of patients.
Patients who are hypersensitive to tocainide or to local anesthetics of the amide type should not be exposed to tocainide. The presence of second- or third-degree heart block in the absence of an artificial pacemaker also con-traindicates the use of tocainide.
When used with other class IB antiarrhythmic drugs, to-cainide toxicity may be increased without significant gain in antiarrhythmic efficacy.