PROCAINAMIDE HCL
Clinical safety rating: safe
Other drugs that prolong the QT interval increase risk of torsades de pointes Can cause lupus-like syndrome and blood dyscrasias.
Class Ia antiarrhythmic agent; blocks sodium channels, decreases phase 0 slope of action potential, prolongs refractory period, and increases action potential duration.
| Metabolism | Hepatic via N-acetyltransferase (NAT2) to N-acetylprocainamide (NAPA); also undergoes hydrolysis to p-aminobenzoic acid. |
| Excretion | Primarily renal (50-60% unchanged via glomerular filtration and tubular secretion) with 10-30% as N-acetylprocainamide (NAPA) metabolite; minor biliary/fecal (<5%). |
| Half-life | Terminal elimination half-life: 2.5-4.7 hours (3 hours typical) in normal renal function; prolonged to 11-20 hours in renal impairment; NAPA half-life 6-8 hours (prolonged in renal failure). |
| Protein binding | 15-25% bound primarily to alpha-1-acid glycoprotein and albumin. |
| Volume of Distribution | 1.5-2.5 L/kg (approximates total body water; indicates extensive tissue distribution). |
| Bioavailability | Oral: 75-95% (immediate-release); IM: 100%; IV: 100%. |
| Onset of Action | IV: 1-5 minutes; IM: 10-15 minutes; Oral: 30-60 minutes (immediate-release). |
| Duration of Action | IV/IM: 3-4 hours (antiarrhythmic effect); Oral immediate-release: 3-6 hours; extended-release: 8-12 hours (dosing interval). |
For life-threatening ventricular arrhythmias, IV: Loading dose: 100 mg administered at a rate of 25-50 mg/min, may repeat every 5 minutes until arrhythmia suppressed or up to a total of 500-1000 mg. Maintenance: IV infusion 1-4 mg/min. Oral: 250-500 mg every 3-6 hours; maximum 4 g/day.
| Dosage form | Injectable |
| Renal impairment | CrCl >50 mL/min: No adjustment. CrCl 10-50 mL/min: Administer every 6-12 hours. CrCl <10 mL/min: Administer every 12-24 hours. |
| Liver impairment | Child-Pugh Class A: No adjustment. Child-Pugh Class B: Reduce dose by 25-50%. Child-Pugh Class C: Reduce dose by 50-75% or avoid use. |
| Pediatric use | IV: Loading dose: 15 mg/kg over 30-60 minutes, followed by maintenance infusion of 20-80 mcg/kg/min; maximum 2 g/day. Oral: 15-50 mg/kg/day in divided doses every 3-6 hours; maximum 4 g/day. |
| Geriatric use | Start at lower end of dosing range due to age-related decreased renal function and increased risk of hypotension and arrhythmias. Monitor renal function and adjust accordingly. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Other drugs that prolong the QT interval increase risk of torsades de pointes Can cause lupus-like syndrome and blood dyscrasias.
| FDA category | Animal |
| Breastfeeding | Procainamide and its active metabolite NAPA are excreted into breast milk. Milk-to-plasma ratio is approximately 0.8-1.3. Concentrations in milk can reach therapeutic levels. Potential for adverse effects in nursing infant, including bradycardia and hypotension. Use with caution, monitor infant. AAP recommends avoiding use if possible. |
| Teratogenic Risk |
■ FDA Black Box Warning
Procanamide can cause agranulocytosis, leukopenia, and thrombocytopenia; fatal blood dyscrasias have occurred. Frequent blood counts are recommended.
| Common Effects | Lupus-like syndrome |
| Serious Effects |
Complete heart block; second- or third-degree AV block without pacemaker; long QT syndrome; torsades de pointes; known hypersensitivity to procainamide or any component.
| Precautions | May cause lupus erythematosus-like syndrome (especially with slow acetylator phenotype); proarrhythmic effects (torsades de pointes); hypotension; bone marrow suppression; hepatotoxicity; potentiation of neuromuscular blocking agents. |
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| FDA pregnancy category C. Procainamide crosses the placenta. In first trimester, risk of congenital anomalies is not well-studied; animal studies show no teratogenicity but use only if clearly needed. In second and third trimesters, chronic use may be associated with fetal bradycardia, QT prolongation, and neonatal lupus syndrome (transient). Avoid in pregnancy if possible. |
| Fetal Monitoring | Monitor maternal ECG (QTc interval), procainamide and NAPA serum concentrations, renal function, complete blood count (risk of agranulocytosis). Fetal monitoring: assess fetal heart rate and rhythm, consider fetal echocardiography for QT interval if maternal treatment prolonged. |
| Fertility Effects | No known adverse effects on human fertility. Animal studies have not been conducted. Procainamide does not affect gonadotropin levels. Limited data; no specific fertility impairment reported. |