Generic name: encainide hydrochloride
Dosage form: Capsules
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As with other antiarrhythmic agents, ENKAID therapy in patients with sustained ventricular tachycardia should be initiated in a hospital setting with facilities for cardiac rhythm monitoring. Hospitalization is also recommended for patients with sinus node dysfunction or cardiomyopathy and/or congestive heart failure even if there is no history of sustained ventricular tachycardia, and at the time of a dose increase to 200 mg per day or above.
ENKAID should be administered only after appropriate clinical assessment and the dosage of ENKAID must be individualized for each patient on the basis of therapeutic response and tolerance.
The recommended initial dosing schedule for adults is one 25 mg ENKAID capsule t.i.d. at approximately 8-hour intervals. After a period of 3 to 5 days, the dosage may be increased to 35 mg t.i.d. if necessary. If the desired therapeutic response is not achieved after an additional 3 to 5 days, the dose may again be adjusted to 50 mg t.i.d. Rapid dose escalation should be avoided.
Patients with hepatic disease or severe renal impairment may require dose and/or dosing interval adjustment (See PRECAUTIONS).
Dosages of ENKAID should be adjusted gradually allowing 3 to 5 days between dosing increments.
This will allow all patients (even the minority that metabolize the drug very slowly), to achieve “steady state” blood levels of encainide and its active metabolites before increasing the dose. Gradual dose adjustments will help prevent the usage of doses which are higher than necessary to control the arrhythmia and which may increase the risk of proarrhythmic events.
In an occasional patient, the dosage may have to be increased to 50 mg q.i.d. to achieve the desired therapeutic response. Higher doses are not normally recommended. However, after the careful dose titration as described above has failed, patients with documented life-threatening arrhythmias may be treated with up to 75 mg q.i.d. Patients should be hospitalized at the time of these dose increases to 200 mg per day or above. Once the desired therapeutic response is achieved, many patients can be adequately maintained on chronic therapy at doses lower than the maximum achieved during titration.
Patients with malignant arrhythmias who exhibit a beneficial response as judged by objective criteria (Holter monitoring, programmed electrical stimulation, exercise testing, etc.) can be maintained on chronic ENKAID therapy.
Some patients whose arrhythmias are well controlled by dosages of 50 mg t.i.d. or less may be transferred to a 12-hour dosage regimen if necessary to increase convenience and help assure compliance. Only those patients who have had an adequate response to 50 mg t.i.d. or less should be transferred to a 12-hour dosage regimen. The total daily dose may be given in two equally divided doses at approximately 12-hour intervals and the patient should be carefully monitored to ensure that an adequate suppression of ventricular ectopy is maintained. The maximum single dose that should be utilized is 75 mg.
Use of higher initial doses and more rapid dosage adjustments have resulted in an increased incidence of proarrhythmic events particularly during the first few days of dosing, therefore, a loading dose is not recommended.
Although limited experience with the concomitant use of ENKAID and intravenous lidocaine has revealed no adverse effects, there are no formal studies to demonstrate the utility of such combined therapy. Clinical experience on transferring patients to ENKAID from another antiarrhythmic drug is also limited. As a general principle, antiarrhythmic therapy should be withdrawn for two to four plasma half-lives before ENKAID is started. If withdrawing antiarrhythmic therapy is potentially life-threatening, consideration should be given to hospitalization.
Facilities for determining plasma levels of encainide and its metabolites are not readily available and the utility of such measurements in guiding the care of patients has not been demonstrated.