CAS Number: 22059-60-5
Norpace | 22059-60-5
Disopyramide Phosphate (brand name Norpace®) is a Class IA antiarrhythmic agent that primarily blocks fast sodium channels, thereby prolonging the cardiac action potential and refractory period. It is indicated mainly for treating serious ventricular arrhythmias such as sustained ventricular tachycardia and premature ventricular contractions, though it is less commonly used today due to significant anticholinergic side effects (including dry mouth, urinary retention, and constipation), negative inotropic effects that can worsen heart failure, and the risk of QT prolongation leading to torsades de pointes. With an oral bioavailability of approximately 83%, hepatic metabolism via CYP3A4, and renal excretion, its half-life is significantly prolonged in renal impairment, necessitating dose adjustment. Despite a decline in routine use because of better-tolerated alternatives like amiodarone and catheter ablation, disopyramide retains a niche role in hypertrophic cardiomyopathy for its negative inotropic properties and in patients intolerant to other antiarrhythmics.
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References
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Disopyramide (Norpace®)-induced hypoglycemia
Disopyramide (Norpace®) is a recently released antiarrhythmic agent with quinidine-like actions, but structurally unique. We describe a patient in whom impressive hypoglycemia developed following treatment with this agent. Blood glucose levels returned to normal after cessation of therapy, but dropped again following rechallenge with the drug. The pathogenesis of the hypoglycemia was investigated by assessment of serum insulin, plasma glucagon and serum alanine levels during disopyramide rechallenge. Clinicians should be aware of fasting hypoglycemia as an unusual but potentially serious complication of disopyramide therapy.
DOI: 10.1016/0002-9343(80)90020-0 -
The effects of disopyramide phosphate on serum glucose and glucose counterregulation in the dog
The effect of oral administration of the antiarrhythmic disopyramide phosphate (DPP) on serum glucose and glucose counterregulation was determined in beagle dogs. In addition, the hypoglycemic effect of DPP, a racemate, and its optical isomers was determined. DPP produced dose-dependent significant decreases in serum glucose concentrations. Maximum decreases in serum glucose concentrations were approximately 10% at 10 mg/kg, 15% at 30 mg/kg, and 30% at 100 mg/kg when DPP was given as single doses, and 30% at 100 mg/kg when DPP was given as three divided doses. In each case, serum glucose concentrations returned to control values within 24 to 30 hr. To evaluate the effect of DPP on glucose counterregulation the recovery from acute insulin-induced hypoglycemia was determined. No differences of any practical significance were observed between the insulin tolerance curves of control and 50-, and 100-mg/kg DPP groups. Thus, the overall glucose counterregulatory response following insulin challenge was unaffected by DPP. The hypoglycemic effects of DPP, (S)-(+)-DPP, and (R)-(−)-DPP were compared by examining the ratio of the areas under the curve of serum glucose concentration to serum drug concentration. The absolute ratio for the (S)-(+) isomer was significantly greater than that of the (R)-(−) isomer, indicating that the hypoglycemic effect of DPP is largely due to its (S)-(+) isomer.
DOI: 10.1016/0272-0590(85)90101-0