PROCAN
Clinical safety rating: caution
Comprehensive clinical and safety monograph for PROCAN (PROCAN).
Procainamide is a class Ia antiarrhythmic agent that blocks sodium channels, slowing conduction velocity and prolonging the refractory period. It also has weak anticholinergic effects.
| Metabolism | Procainamide is primarily metabolized by N-acetyltransferase (NAT2) to N-acetylprocainamide. It also undergoes hepatic hydrolysis. |
| Excretion | Renal: 50-67% as unchanged drug and major metabolite N-acetylprocainamide (NAPA). Biliary/fecal: <10%. |
| Half-life | Procainamide: 2.5-4.7 hours (increased to 4-6 hours in elderly or heart failure; prolonged in renal impairment). NAPA: 6-9 hours (active metabolite). Clinical context: Therapeutic monitoring requires measurement of both parent drug and metabolite due to NAPA's antiarrhythmic activity. |
| Protein binding | Procainamide: 15-20% bound to albumin. NAPA: 10-15% bound to albumin. |
| Volume of Distribution | Procainamide: 1.5-2.5 L/kg. NAPA: 1.2-1.7 L/kg. Clinical meaning: Large Vd indicates extensive tissue distribution (e.g., heart, liver, brain). |
| Bioavailability | Oral: 75-95% (immediate-release). Sustained-release: 90% relative to IR. IM: 85-100%. |
| Onset of Action | IV: 3-5 minutes. Oral: 30 minutes to 1 hour. IM: 10-15 minutes. |
| Duration of Action | IV: 1-2 hours. Oral: 2-4 hours (immediate-release). Sustained-release: 6-8 hours. Duration prolonged in renal impairment or heart failure. |
250 mg orally every 6 hours; extended-release product: 500 mg orally every 6 hours.
| Dosage form | CAPSULE |
| Renal impairment | For CrCl 10-50 mL/min: administer 50% of normal dose every 6 hours; for CrCl <10 mL/min: administer 25% of normal dose every 8 hours. |
| Liver impairment | No specific guidelines; caution in severe impairment due to risk of toxicity. |
| Pediatric use | 25 to 50 mg/kg/day orally in divided doses every 6 hours; not to exceed 4 g/day. |
| Geriatric use | Start at lower end of dosing range; monitor renal function due to age-related decline; usual adult dosing with caution. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for PROCAN (PROCAN).
| Breastfeeding | Excreted in breast milk (M/P ratio ~0.9). Limited data; avoid breastfeeding due to potential for neonatal bradycardia and cyanosis. |
| Teratogenic Risk | FDA Pregnancy Category C. In first trimester, risk of spontaneous abortion; second/third trimester, risk of fetal bradycardia and arrhythmias. No structural teratogenicity documented in humans. |
| Fetal Monitoring | Maternal: ECG for arrhythmias, heart rate, blood pressure, procainamide levels (target 4-10 mcg/mL), ANA titer. Fetal: heart rate monitoring during labor. |
■ FDA Black Box Warning
Procainamide can cause blood dyscrasias including agranulocytosis, leukopenia, thrombocytopenia, and aplastic anemia. Regular hematologic monitoring is required.
| Serious Effects |
Complete heart block, second- or third-degree AV block (unless paced), torsade de pointes, known hypersensitivity to procainamide or related drugs, lupus erythematosus.
| Precautions | Lupus erythematosus-like syndrome (especially in slow acetylators), QT prolongation and torsade de pointes, proarrhythmic effects, hypotension, heart failure exacerbation, and renal impairment require dose adjustment. |
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| Fertility Effects | No known adverse effects on human fertility. Animal studies suggest no impairment. |