Disopyramide
Mechanism :
Disopyramide is a Type 1 antiarrhythmic drug. It decreases the rate of diastolic depolarization (phase 4) in cells with augmented automaticity, decreases the upstroke velocity (phase 0) and increases the action potential duration of normal cardiac cells, decreases the disparity in refractoriness between infarcted and adjacent normally perfused myocardium, and has no effect on alpha- or beta-adrenergic receptors.
Indication :
Contraindications :
Contraindicated in the presence of cardiogenic shock, pre-existing second- or third-degree AV block (if no pacemaker is present), congenital Q-T prolongation, or known hypersensitivity to the drug.
Dosing :
Give 6 hourly per oral.
<1 year:
10 to 30 mg/kg/day.
1 to 4 years:
10 to 20 mg/kg/day.
4 to 12 years:
10 to 15 mg/kg/day.
12 to 18 years:
6 to 15 mg/kg/day.
Adverse Effect :
Hypotension, congestive heart failure, anticholinergic effects (urinary retention, urinary urgency, constipation, flatulence, blurred vision, dry eyes), impotence, dry throat, weight gain, anorexia, vomiting, allergic rash, hypokalemia, muscle weakness, chest pain, hypoglycemia, lupus, peripheral neuropathy, sleep disturbances.
Interaction :
Phenytoin may lower plasma levels of disopyramide. Monitoring of disopyramide plasma levels is recommended in such concurrent use to avoid ineffective therapy. Other antiarrhythmic drugs (e.g., quinidine, procainamide, lidocaine, propranolol) have occasionally been used concurrently. Excessive widening of the QRS complex and/or prolongation of the Q-T interval may occur in these situations.
Quinidine: Concomitant administration with quinidine resulted in slight increases in plasma disopyramide levels and slight decreases in plasma quinidine levels.
Erythromycin: Patients taking disopyramide phosphate and erythromycin concomitantly may develop increased serum concentrations of disopyramide resulting in excessive widening of the QRS complex and/or prolongation of the Q-T interval.
Renal Dose :
Dose in Renal Impairment GFR (mL/min)
| 20-50 | Oral: 100 mg every 8 hours or 150 mg every 12 hours |
| 10-20 | Oral: 100 mg every 12 hours |
| <10 | Oral: 150 mg every 24 hours (monitor levels) |
Dose in Patients undergoing Renal Replacement Therapies
| CAPD | Not dialysed. Dose as in GFR<10 mL/min |
| HD | Not dialysed. Dose as in GFR<10 mL/min |
| HDF/High flux | Unlikely to be dialysed. Dose as in GFR<10 mL/min |
| CAV/VVHD | Unknown dialysability. Dose as in GFR=10–20 mL/min |
Hepatic Dose :
Hepatic impairment causes an increase in the plasma half-life of Disopyramide and a reduced dosage may be required.