Norpace (disopyramide phosphate) is an antiarrhythmic
drug available for oral
in immediate-release and controlled-release capsules containing
100 mg or 150 mg
of disopyramide base, present
as the phosphate. The base
content of the phosphate
salt is 77.6% .
Norpace is freely soluble
in water, and the free base
(pKa 10.4) has an aqueous
solubility of 1 mg/ml.
The chloroform: water partition coefficient of the base
is 3.1 at pH 7.2.
Norpace is a racemic
mixture of d- and
I-isomers. This drug is not chemically related to other antiarrhythmic
Norpace CR (controlled-release)
capsules are designed to afford a gradual and consistent release
of disopyramide. Thus, for maintenance therapy, Norpace CR
provides the benefit
of less-frequent dosing (every 12 hours) as compared with the every-6-hour
of immediate-release Norpace capsules.
Inactive ingredients of Norpace include corn
ink, FD&C Red No. 3, FD&C Yellow No. 6, gelatin, lactose,
talc, and titanium dioxide; the 150-mg capsule
also contains FD&C Blue No. 1.
Inactive ingredients of Norpace CR
include corn starch,
D&C Yellow No. 10, edible
ink, ethylcellulose, FD&C Blue No. 1, gelatin, shellac, sucrose,
talc, and titanium
dioxide; the 150-mg capsule
also contains FD&C Red No. 3 and FD&C Yellow No. 6.