Disopyramide is indicated for the ventricular arrhythmias, especially after myocardial infarction, supraventricular arrhythmias.
Membrane stabilizing agent (Sodium channel blockers)
Disopyramide’s Class 1a activity is similar to that of quinidine in that it targets sodium channels to inhibit conduction. Disopyramide depresses the increase in sodium permeability of the cardiac Myocyte during Phase 0 of the cardiac action potential, in turn decreasing the inward sodium current. This results in an increased threshold for excitation and a decreased upstroke velocity.
Disopyramide prolongs the PR interval by lengthening both the QRS and P wave duration. This effect is particularly well suited in the treatment of ventricular tachycardia as it slows the action potential propagation through the atria to the ventricles.
Disopyramide does not act as a blocking agent for beta or alpha adrenergic receptors, but does have a significant negative inotropic effect on the ventricular myocardium. As a result, the use of disopyramide may reduce contractile force up to 42% at low doses and up to 100% in higher doses leading to heart failure.
This provides a possible treatment for atrial and ventricular fibrillation, as it restores pacemaker control of the tissue to the SA and AV nodes
The recommended dose of Disopyramide is 400 mg /day in 4 divided doses (100 mg capsule 6 hourly).
Patients with renal insufficiency should take 100 mg capsule according to the schedule given below:
Creatinine clearance (ml/min) >15: Approximate dosing q 8 hrq 12 hrq 24 hr
Patients in whom rapid control of ventricular arrhythmia is essential, an initial loading dose of 300 mg Disopyramide is recommended, followed by the appropriate maintenance dosage.
Disopyramide is contraindicated in the pre-existing A-V heart block, shock, glaucoma, urinary retention and known hypersensitivity to the drug.
Usually Disopyramide is well tolerated but occasionally in some cases dry mouth/ nose/ eye, nausea, vomiting, diarrhea, bloating, blurred vision, urinary problems, headache, skin rash, dizziness, nervousness & impotence (1-3%) may occur.
There are no adequate and well-controlled studies in pregnant women. Disopyramide should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus.
Lactation: Because of the potential for serious adverse reactions in nursing infants from Disopyramide, a decision should be made whether to discontinue nursing or to discontinue the drug , taking into account the importance of the drug to the mother
Disopyramide should not be administered to patients with cardiomyopathy and associated congestive heart failure unless the patient is digitalized and adequately compensated. Disopyramide should be used with caution in the presence of digitalis intoxication.
Deliberate or accidental over dosage of oral Disopyramide may be followed by apnea, loss of consciousness & loss of spontaneous respiration. In such a case immediate hospitalization and all life saving measures should be taken.