procainamide

Absorption: IV administration results in complete bioavailability.

Distribution: Widely distributed to tissues.

Metabolism/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)

ROUTE	ONSET	PEAK	DURATION
IV	immediate	25–60 min	3–4 hr

Contraind./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.

Adv. 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

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.

Toxicity and Overdose:

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 ⬆ ⬇

IV Administration:

(only to be used for life-threatening arrhythmias).
Diluent: Dilute each 100 mg of procainamide with 10 mL of 0.9% NaCl.
Rate: Not to exceed 25 mg/min. Rapid administration may cause ventricular fibrillation or asystole.
Intermittent Infusion: Diluent: Add 2 g of procainamide to 250 mL of 0.9% NaCl. Concentration: 8 mg/mL.
Rate: Administer initial infusion over 30–60 min. Administer maintenance infusion at rate of 1–4 mg/min to maintain control of arrhythmia.

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.

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Pronunciation ⬇

Classifications ⬆ ⬇

Indications ⬆ ⬇

Action ⬆ ⬇

Pharmacokinetics ⬆ ⬇