tocainide hydrochloride
Tonocard

Available forms
Available by prescription only
Tablets: 400 mg, 600 mg

Indications and dosages
 Treatment of life-threatening ventricular arrhythmias.  Individualize dosage based on antiarrhythmic response and tolerance.
Adults: Initially, 400 mg P.O. q 8 hours. Usual dose is between 1,200 and 1,800 mg daily, divided into three doses. Drug may be given in a b.i.d. regimen if patient is able to tolerate the t.i.d. regimen.
≡ Dosage adjustment. Patients with impaired renal or hepatic function may be adequately treated with less than 1,200 mg daily.
 Myotonic dystrophy ◇. Adults: 800 to 1,200 mg P.O. daily.

Pharmacodynamics
Antiarrhythmic action: Tocainide is structurally similar to lidocaine and possesses similar electrophysiologic and hemodynamic effects. A class IB antiarrhythmic, it suppresses automaticity and shortens the effective refractory period and action potential duration of His-Purkinje fibers and suppresses spontaneous ventricular depolarization during diastole. Conductive atrial tissue and AV conduction aren’t affected significantly at therapeutic levels. Unlike quinidine and procainamide, tocainide doesn’t significantly alter hemodynamics when administered in usual doses. Tocainide exerts its effects on the conduction system, causing inhibition of reentry mechanisms and cessation of ventricular arrhythmias; these effects may be more pronounced in ischemic tissue. Tocainide doesn’t cause a significant negative inotropic effect. Its direct cardiac effects are less potent than those of lidocaine.

Pharmacokinetics
Absorption: Rapidly and completely absorbed from the GI tract; unlike lidocaine, it undergoes negligible first-pass effect in the liver. Bioavailability is nearly 100%.
Distribution: Distribution is only partially understood; however, it appears to be distributed widely and apparently crosses the blood-brain barrier and placenta in animals (it is, however, less lipophilic than lidocaine). Only about 10% to 20% is bound to plasma protein.
Metabolism: Apparently metabolized in the liver to inactive metabolites.
Excretion: Excreted in urine as unchanged drug and inactive metabolites. About 30% to 50% of an orally administered dose is excreted in urine as metabolites. Elimination half-life is about 11 to 23 hours, with an initial biphasic plasma level decline similar to that of lidocaine. Half-life may be prolonged in patients with renal or hepatic insufficiency. Urine alkalinization may substantially decrease the amount of unchanged drug excreted in urine.

Contraindications and precautions
Contraindicated in patients hypersensitive to lidocaine or other amide-type local anesthetics and in those with second- or third-degree AV block in the absence of an artificial pacemaker.
  Use cautiously in patients with heart failure, diminished cardiac reserve, bone marrow failure, cytopenia, or impaired renal or hepatic function.

Interactions
Drug-drug. Allopurinol: Increases allopurinol effects. Monitor patient carefully.
Antiarrhythmics: Causes additive, synergistic, or antagonistic effects. Monitor cardiac status closely.
Cimetidine, rifampin: Decreases elimination half-life and bioavailability of tocainide. Monitor patient carefully. Dosage adjustment may be needed.
Lidocaine: May cause CNS toxicity. Monitor patient closely.
Metoprolol: Decreases myocardial contractility and bradycardia. Monitor cardiac status.

Adverse reactions
CNS: light-headedness, tremor, paresthesia, dizziness, vertigo, drowsiness, fatigue, confusion, headache.
CV: hypotension, new or worsened arrhythmias, heart failure, bradycardia, palpitations.
EENT: blurred vision, tinnitus.
GI: nausea, vomiting, diarrhea, anorexia.
Hematologic: blood dyscrasia.
Hepatic: hepatitis.
Respiratory: respiratory arrest, pulmonary fibrosis, pneumonitis,pulmonary edema.
Skin: rash, diaphoresis.

Effects on lab test results
• May decrease hemoglobin, hematocrit, and platelet and granulocyte counts. May increase or decrease liver function test values.

Overdose and treatment
Effects of overdose include extensions of common adverse reactions, particularly those related to the CNS or GI tract.
 Treatment generally involves symptomatic and supportive care. In acute overdose, induce emesis or perform gastric lavage. Respiratory depression necessitates immediate attention and maintenance of a patent airway with ventilatory assistance, if required. Seizures may be treated with small incremental doses of a benzodiazepine, such as diazepam or a short- or ultrashort-acting barbiturate, such as pentobarbital or thiopental.

Special considerations
• Drug is considered an oral lidocaine and may be used to ease transition from I.V. lidocaine to oral antiarrhythmic therapy.
• Use cautiously and with lower doses in patients with hepatic or renal impairment.
• A chest radiograph should be obtained if pulmonary symptoms exist.
• Adverse effects tend to be frequent and problematic.
• Monitor blood levels; therapeutic levels range from 4 to 10 mcg/ml.
• Monitor periodic blood counts for the first 3 months of therapy and frequently thereafter. Perform CBC promptly if signs of infection develop.
• Observe patient for tremors, a possible sign that maximum safe dose has been reached.
Pregnant patients
• Use drug during pregnancy only when potential benefits justify possible risks to fetus.
Breast-feeding patients
• Safety in breast-feeding women hasn’t been established. An alternative to breast-feeding is recommended.
Pediatric patients
• Safety and efficacy haven’t been established.
Geriatric patients
• Use cautiously in elderly patients; increased serum drug levels and toxicity are more likely. Monitor patient carefully.
• Elderly patients are more likely to become dizzy and may need assistance walking.

Patient education
• Instruct patient to report unusual bleeding or bruising; signs or symptoms of infection, such as fever, sore throat, stomatitis, or chills; or pulmonary symptoms, such as cough, wheezing, or exertional dyspnea.
• Tell patient he may take tocainide with food to lessen GI upset.
• Tell patient that tocainide may cause drowsiness or dizziness, and he should be careful while performing tasks that require alertness.

Reactions may be common, uncommon, life-threatening, or COMMON AND LIFE THREATENING.
◆ Canada only
◇ Unlabeled clinical use