Norpace (disopyramide phosphate) is an anti-arrhythmic drug available for oral administration 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%. The structural formula of Norpace is:

α-[2-(diisopropylamino) ethyl]-α-phenyl-2-pyridineacetamide phosphate

Norpace is freely soluble in water, and the free base (pKa 10.4) has an aqueous solubility of 1mg/ml. The chloroform: water partition coefficient of the base is 3.1 at pH 7.2.

Norpace is a racemic mixture of d- and l- isomers. This drug is not chemically related to other anti-arrhythmic drugs.

Norpace CR (controlled-release) capsules are designed to afford a gradual and consistent release of disopyramide. Thus, for maintenance therapy, Nor-pace CR provides the benefit of less-frequent dosing (every 12 hours) as compared with the every-6-hour dosage schedule of immediate-release Norpace capsules.

Inactive ingredients of Norpace include corn starch, edible 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.

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