procainamide

General

Genetic Implications:

Pronunciation:
proe-kane-ah-mide

Trade Name(s)

• Pronestyl

Ther. Class.

antiarrhythmics

(class IA)

Indications

Ventricular and atrial arrhythmias, including:

• Ventricular tachycardia,
• Atrioventricular reentrant tachycardia,
• Atrial fibrillation

Action

• Decreases myocardial excitability.
• Slows conduction velocity.
• May depress myocardial contractility.

Therapeutic Effect(s):

Suppression of arrhythmias.

Pharmacokinetics

Absorption: IV administration results in complete bioavailability.

Distribution: Widely distributed to tissues.

Metabolism and Excretion: Converted by the liver by N-acetyltransferase to  N -acetylprocainamide (NAPA), an active antiarrhythmic compound;  rate of acetylation is genetically determined (slow acetylators have ↑ procainamide levels and ↑ risk of toxicity; fast acetylators have ↓ procainamide levels and ↑ risk for treatment failure). 40–70% excreted unchanged by the kidneys.

Half-life: 2.5–4.7 hr (NAPA: 7 hr); ↑ in renal impairment.

TIME/ACTION PROFILE (antiarrhythmic effects)

Contraindication/Precautions

Contraindicated in:

• Hypersensitivity;
• AV block;
• Myasthenia gravis;
• Lactation:  Lactation.

Use Cautiously in:

• MI or digoxin toxicity;
• HF, renal impairment, or hepatic impairment (dose ↓ recommended);
• OB:   Safety not established in pregnancy;
• Pedi:   Safety and effectiveness not established in children;
• Geri:  Dose ↓ recommended.

Adverse Reactions/Side Effects

CV: ASYSTOLE, HEART BLOCK, hypotension, VENTRICULAR ARRHYTHMIAS

Derm: rash

GI: diarrhea, anorexia, nausea, vomiting

Hemat: AGRANULOCYTOSIS, eosinophilia, leukopenia, thrombocytopenia

Neuro: confusion, dizziness, SEIZURES

Misc: chills, drug-induced lupus, fever

* CAPITALS indicate life-threatening.
Underline indicate most frequent.

Interactions

Drug-Drug

• May have additive or antagonistic effects with other  antiarrhythmics.
• Additive neurologic toxicity (confusion, seizures) with  lidocaine.
•  Antihypertensives  and  nitrates  may potentiate hypotensive effect.
• Potentiates  neuromuscular blocking agents.
• May partially antagonize the therapeutic effects of  anticholinesterase agents  in myasthenia gravis.
• ↑ risk of arrhythmias with  pimozide.
• Additive anticholinergic effects with other  drugs possessing anticholinergic properties, including  antihistamines,  antidepressants,  atropine,  haloperidol, and  phenothiazines.
• Effects of procainamide may be ↑ by  cimetidine,  quinidine, or  trimethoprim.

Route/Dosage

IV (Adults): 100 mg every 5 min until arrhythmia is abolished or 1000 mg have been given; wait at least 10 min until further dosing   or  loading infusion of 500–600 mg over 30–60 min followed by maintenance infusion of 1–4 mg/min.

Availability (generic available)

Solution for injection: 100 mg/mL, 500 mg/mL

Assessment

• Monitor ECG, pulse, and BP continuously throughout IV administration. Parameters should be monitored periodically during oral administration. IV administration is usually discontinued if any of the following occur: arrhythmia is resolved, QRS complex widens by 50%, PR interval is prolonged, BP drops >15 mm Hg, or toxic side effects develop. Patient should remain supine throughout IV administration to minimize hypotension.

Lab Test Considerations:

Monitor CBC every 2 wk during the first 3 mo of therapy. May cause ↓ leukocyte, neutrophil, and platelet counts. Therapy may be discontinued if leukopenia occurs. Blood counts usually return to normal within 1 mo of discontinuation of therapy.

• Monitor ANA periodically during prolonged therapy or if symptoms of lupus-like reaction occur. Therapy is discontinued if a steady increase in ANA titer occurs.
• May cause ↑ AST, ALT, alkaline phosphatase, LDH, bilirubin, and a positive Coombs' test result.

Serum procainamide and NAPA levels may be monitored periodically during dosage adjustment. Therapeutic blood level of procainamide is 4–8 mcg/mL.

• Toxicity may occur with procainamide blood levels of 8–16 mcg/mL or greater.
• Signs of toxicity include confusion, dizziness, drowsiness, decreased urination, nausea, vomiting, and tachyarrhythmias.

Implementation

Patient/Family Teaching

• May cause dizziness. Caution patient to request assistance with ambulation until response to medication is known.
• Advise patient to notify health care professional immediately if signs of drug-induced lupus syndrome (fever, chills, joint pain or swelling, pain with breathing, skin rash), leukopenia (sore throat, mouth, or gums), or thrombocytopenia (unusual bleeding or bruising) occur. Medication may be discontinued if these occur.
• Rep:  Advise females of reproductive potential to notify health care professional if pregnancy is planned or suspected and to avoid breastfeeding.
• Advise patient to carry identification at all times describing disease process and medication regimen.
• Emphasize the importance of routine follow-up exams to monitor progress.

Evaluation/Desired Outcomes

Resolution of cardiac arrhythmias without detrimental side effects.