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Procainamide (Procainamide Hydrochloride) - Indications and Dosage

 
 



INDICATIONS AND USAGE

Procainamide hydrochloride injection is indicated for the treatment of documented ventricular arrhythmias, such as sustained ventricular tachycardia, that, in the judgement of the physician, are life-threatening. Because of the proarrhythmic effects of procainamide, its use with lesser arrhythmias is generally not recommended. Treatment of patients with asymptomatic ventricular premature contractions should be avoided.

Initiation of procainamide treatment, as with other antiarrhythmic agents used to treat life-threatening arrhythmias, should be carried out in the hospital.

Antiarrhythmic drugs have not been shown to enhance survival in patients with ventricular arrhythmias.

Because procainamide has the potential to produce serious hematological disorders (0.5 percent) particularly leukopenia or agranulocytosis (sometimes fatal), its use should be reserved for patients in whom, in the opinion of the physician, the benefits of treatment clearly outweigh the risks. (see  WARNINGS and Boxed Warning.)

DOSAGE AND ADMINISTRATION

Procainamide Hydrochloride Injection is useful for arrhythmias which require immediate suppression and for maintenance of arrhythmia control. Intravenous therapy allows most rapid control of serious arrhythmias, including those following myocardial infarction; it should be carried out in circumstances where close observation and monitoring of the patient are possible, such as in hospital or emergency facilities. Intramuscular administration is less apt to produce temporary high plasma levels but therapeutic plasma levels are not obtained as rapidly as with intravenous administration. Oral procainamide dosage forms are preferable for less urgent arrhythmias as well as for long-term maintenance after initial parenteral PA therapy.

Intramuscular administration may be used as an alternative to the oral route for patients with less threatening arrhythmias but who are nauseated or vomiting, who are ordered to receive nothing by mouth preoperatively, or who may have malabsorptive problems. An initial daily dose of 50 mg per kg body weight may be estimated. This amount should be divided into fractional doses of one-eighth to one-quarter to be injected intramuscularly every three to six hours until oral therapy is possible. If more than three injections are given, the physician may wish to assess patient factors such as age and renal function (see below), clinical response and, if available, blood levels of PA and NAPA in adjusting further doses for that individual. For treatment of arrhythmias associated with anesthesia or surgical operation, the suggested dose is 100 to 500 mg by intramuscular injection.

Intravenous administration of Procainamide Hydrochloride Injection should be done cautiously to avoid a possible hypotensive response (see  PRECAUTIONS and OVERDOSAGE ). Initial arrhythmia control, under ECG monitoring, may usually be accomplished safely within a half-hour by either of the two methods which follows:

a) Direct injection into a vein or into tubing of an established infusion line should be done slowly at a rate not to exceed 50 mg per minute. It is advisable to dilute either the 100 mg/mL or the 500 mg/mL concentrations of procainamide hydrochloride prior to intravenous injection to facilitate control of dosage rate. Doses of 100 mg may be administered every 5 minutes at this rate until the arrhythmia is suppressed or until 500 mg has been administered, after which it is advisable to wait 10 minutes or longer to allow for more distribution into tissues before resuming.

b) Alternatively, a loading infusion containing 20 mg of Procainamide Hydrochloride per mL (1 g diluted to 50 mL with 5% Dextrose Injection, USP) may be administered at a constant rate of 1 mL per minute for 25 to 30 minutes to deliver 500 to 600 mg of PA. Some effects may be seen after infusion of the first 100 or 200 mg; it is unusual to require more than 600 mg to achieve satisfactory antiarrhythmic effects.

The maximum advisable dosage to be given either by repeated bolus injections or such loading infusion is 1 g.

To maintain therapeutic levels, a more dilute intravenous infusion at a concentration of 2 mg/mL is convenient (1000 mg procainamide HCl in 500 mL of 5% Dextrose Injection, USP), and may be administered at 1 to 3 mL/minute. If daily total fluid intake must be limited, a 4 mg/mL concentration (1 g of Procainamide Hydrochloride Injection in 250 mL of 5% Dextrose Injection, USP) administered at 0.5 to 1.5 mL/minute will deliver an equivalent 2 to 6 mg per minute. The amount needed in a given patient to maintain the therapeutic level should be assessed principally from the clinical response, and will depend upon the patient’s weight and age, renal elimination, hepatic acetylation rate, and cardiac status, but should be adjusted for each patient based upon close observation. A maintenance infusion rate of 50 mcg/min/kg body weight to a person with a normal renal PA elimination half-time of three hours may be expected to produce a plasma level of approximately 6.5 mcg/mL.

Since the principal route for elimination of PA and NAPA is renal excretion, reduced excretion will prolong the half-life of elimination and lower the dose rate needed to maintain therapeutic levels. Advancing age reduces the renal excretion of PA and NAPA independently of reductions in creatinine clearance; compared to normal young adults, there is approximately 25 percent reduction at age 50 and 50 percent at age 75.

Intravenous therapy should be terminated if persistent conduction disturbances or hypotension develop. As soon as the patient’s basic cardiac rhythm appears to be stabilized, oral antiarrhythmic maintenance therapy is preferable, if indicated and possible. A period of about three to four hours (one half-time for renal elimination, ordinarily) should elapse after the last intravenous dose before administering the first dose of Procainamide Hydrochloride tablets or capsules.

DILUTIONS AND RATES FOR INTRAVENOUS INFUSIONS*
Procainamide Hydrochloride Injection, USP

Final Concentration

Infusion
Volume

Procainamide
Hydrochloride To Be Added

Infusion
Rate

Initial Loading Infusion

20 mg/mL

50 mL

1000 mg

1 mL/min
(for up to 25–30 min*)

Maintenance Infusion

2 mg/mL

or

4 mg/mL

500 mL

 

250 mL

1000 mg

 

1000 mg

1 to 3 mL/min

 

0.5 to 1.5 mL/min

The maintenance infusion rates are calculated to deliver 2 to 6 mg per minute, depending on body weight, renal elimination rate, and steady-state plasma level needed to maintain control of the arrhythmia*. The 4 mg/mL maintenance concentration may be preferred if total infused volume must be limited.

†(All infusions should be made up to final volume with 5% Dextrose Injection, USP.)
*Please see text under  DOSAGE AND ADMINISTRATION for further details. The flow rate of any intravenous procainamide infusion must be monitored closely to avoid transiently high plasma levels and possible hypotension (see PRECAUTIONS ).

Parenteral drug products should be examined visually for particulate matter and discoloration (see HOW SUPPLIED ) prior to administration.

HOW SUPPLIED

Procainamide Hydrochloride Injection, USP is available in multiple-dose 10 mL vials providing 100 mg procainamide hydrochloride per mL and 2 mL vials providing 500 mg procainamide hydrochloride per mL.

  NDC No.

Container

Concentration

Size

0409-1902-01

Fliptop Vial

100 mg/mL

10 mL

0409-1903-01

Fliptop Vial

500 mg/mL

2 mL

The solutions, which are clear and colorless initially, may develop a slightly yellow color in time. This does not indicate a change which should preclude its use, but a solution any darker than light amber or otherwise discolored should not be used.

Store at 20 to 25°C (68 to 77°F). [See USP Controlled Room Temperature.]

Revised: December, 2007

 

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