Procainamide hydrochloride is available in 10-mL multidose vials providing 100 mg/mL or 2-mL multidose vials providing 500 mg/mL.3400 Each mL of solution in the 10-mL vial also contains methylparaben 1 mg and sodium metabisulfite 0.8 mg in water for injection.3400 Each mL of solution in the 2-mL vial also contains methylparaben 1 mg and sodium metabisulfite 1.8 mg in water for injection.3400 In both vial sizes, the solution also may contain hydrochloric acid and/or sodium hydroxide to adjust the pH.3400
Procainamide hydrochloride also is available in single-dose, prefilled 10-mL syringes providing 100 mg/mL.3401 Prefilled syringes are intended only for use in the preparation of intravenous infusion solutions.3401 Each mL of solution also contains benzyl alcohol 9 mg and sodium bisulfite 0.9 mg in water for injection.3401 The solution also may contain hydrochloric acid and/or sodium hydroxide to adjust the pH.3401
pH
Procainamide hydrochloride injection solution has a pH adjusted to 5 (ranges from 4 to 6).3400; 3401
Procainamide hydrochloride may be administered by intramuscular or direct intravenous injection or intravenous infusion.3400; 3401 Manufacturers recommend that procainamide hydrochloride injection solution be diluted to a final volume with dextrose 5% prior to intravenous use in order to facilitate control of the administration rate.3400; 3401
If procainamide hydrochloride is administered as a direct injection into a vein or into the tubing of an established intravenous line, the drug should be administered slowly, and the rate of administration should not exceed 50 mg/min.3400; 3401 Alternatively, a loading infusion may be administered.3400; 3401 To prepare a 20-mg/mL initial loading infusion, 1 g of procainamide hydrochloride should be diluted to 50 mL with dextrose 5% for intravenous administration at a rate of 1 mL/min for 25 to 30 minutes.3400; 3401
Maintenance infusions of 2 mg/mL or 4 mg/mL (for fluid-restricted patients) should be prepared by diluting 1 g of procainamide hydrochloride to 500 or 250 mL, respectively, with dextrose 5%.3400; 3401 Intravenous infusions with a final concentration of 2 mg/mL may be administered at a rate of 1 to 3 mL/min; infusions with a final concentration of 4 mg/mL may be administered at a rate of 0.5 to 1.5 mL/min.3400; 3401
Intact vials and prefilled syringes of procainamide hydrochloride should be stored at controlled room temperature.3400; 3401 Intact containers are packaged using nitrogen.3400; 3401 Injection of air into the vial causes the solution to darken.40 Sulfites (e.g., sodium metabisulfite) are included in the formulation primarily to prevent discoloration that occurs as a result of oxidation of p-aminobenzoic acid, a degradation product of procainamide hydrochloride.1916 The injection solution is initially colorless, but may turn slightly yellow over time.3400; 3401 Solutions that appear darker than a light amber color or are otherwise discolored should not be used.3400; 3401
Procainamide hydrochloride forms a- and ß-glucosylamine compounds with dextrose.1896 The reaction proceeds rapidly, with about 10% procainamide loss in dextrose 5% occurring in about 5 hours and 30% loss in 24 hours at 25°C.1896 Equilibrium is achieved with about 62% of the procainamide present as glucosylamines.1896 The bioavailability, activity, and metabolic fate of these compounds is not known.546; 1896 The a- and ß-glucosylamine compounds that form are reversible,1422; 1896 although the extent of reversibility in plasma has been questioned.2051 The rate and extent of complex formation are dependent on the dextrose concentration and the solution pH but are independent of the procainamide hydrochloride concentration.1422 In dextrose concentrations ranging from 1 to 5%, the extent of procainamide complex formation ranged from 6% in 2 days in dextrose 1% up to 351422 to 60%1896 in dextrose 5%. Lowering the pH from the normal 4.5 to 1.4 with 0.01 N hydrochloric acid completely prevented complex formation.1422 Similarly, increasing the solution pH to 8 is reported to block complexation.1423 Maximum complex formation occurred at pH 3 to 51423 or 4 to 5.2,1358 the natural pH of procainamide hydrochloride admixtures in dextrose 5%. The clinical importance of this complexation, if any, is uncertain.
Procainamide hydrochloride (Sandoz) 100 mg/mL repackaged in clear glass vials exhibited less than 10% loss in 193 days stored at 23°C when exposed to light and 5°C when protected from light.3402 All solutions of procainamide hydrochloride stored at 23°C exposed to light exhibited an increase or darkening of yellow color; however, the 100-mg/mL solution stored in glass vials exhibited a more intense color as compared with 3-mg/mL solutions diluted in sodium chloride 0.9% stored in polyvinyl chloride (PVC) bags.3402 Solutions stored in either container at 5°C and protected from light did not exhibit such color changes.3402
Sorption
Procainamide hydrochloride was shown not to exhibit sorption to PVC bags and tubing, polyethylene tubing, Silastic tubing, and polypropylene syringes.536; 606
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