PROCAN SR

Clinical safety rating: caution

Comprehensive clinical and safety monograph for PROCAN SR (PROCAN SR).

How it works

Procainamide is a class Ia antiarrhythmic agent that blocks sodium channels, reducing myocardial excitability and conduction velocity, and prolonging the refractory period.

What the body does with it

Metabolism	Hepatic N-acetylation by N-acetyltransferase to N-acetylprocainamide (NAPA); NAPA undergoes further metabolism by CYP2D6 and other pathways.
Excretion	Renal: 50-60% as unchanged procainamide; hepatic metabolism to N-acetylprocainamide (NAPA) which is also renally excreted; total renal excretion of procainamide + NAPA accounts for ~85% of dose; remainder fecal (<5%).
Half-life	Procainamide: 2.5-4.7 hours (normal renal function); NAPA: 6-8 hours. In renal impairment, half-life prolonged up to 10-20 hours for procainamide and 40+ hours for NAPA.
Protein binding	Procainamide: 15-20% bound to plasma proteins (albumin and alpha-1 acid glycoprotein); NAPA: 10% bound.
Volume of Distribution	Procainamide: 2 L/kg (1.5-2.5 L/kg); distributes extensively into tissues, including heart, liver, and kidneys.
Bioavailability	Oral (immediate release): 75-95% (mean 83%); Oral (sustained-release): approximately 80-90% relative to immediate release.
Onset of Action	Oral (immediate release): 30-60 min; Oral (sustained-release): 1-2 hours; IV: immediate (within 1-2 minutes).
Duration of Action	Oral (immediate release): 3-4 hours; Oral (sustained-release): 6-8 hours; IV: 1-2 hours after bolus. Clinical effect correlates with therapeutic plasma concentration of 4-10 mcg/mL (procainamide + NAPA).

Classification & Brands

Dosing & administration

Oral: 50 mg/kg/day divided every 6 hours; typical adult dose: 250-500 mg every 6 hours. For sustained-release (Procan SR): 500-1000 mg every 6 hours.

Dosage form	TABLET, EXTENDED RELEASE
Renal impairment	GFR 30-50 mL/min: administer every 8-12 hours. GFR 15-29 mL/min: administer every 12-24 hours. GFR <15 mL/min: administer every 24-48 hours or avoid use.
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	Oral: 15-50 mg/kg/day divided every 3-6 hours; maximum 4 g/day. For sustained-release: not recommended in children <12 years.
Geriatric use	Start at lower end of dosing range (250 mg every 12 hours for sustained-release) and titrate slowly; monitor for hypotension, bradycardia, and QT prolongation due to reduced renal clearance and comorbidities.

Use during pregnancy

1st trimester	Consult provider
2nd trimester	Consult provider
3rd trimester	Consult provider

Clinical note

Comprehensive clinical and safety monograph for PROCAN SR (PROCAN SR).

Breastfeeding	Present in breast milk; M/P ratio approximately 0.2-0.3. Estimated infant dose <10% maternal weight-adjusted dose. Caution: Monitor infant for rash, agranulocytosis, tachycardia. Usually compatible with breastfeeding.
Teratogenic Risk	FDA Category C. First trimester: Procainamide crosses placenta; risk of fetal cardiac arrhythmias. Second/third trimesters: Potential for hypotension, reduced uterine blood flow, and neonatal thrombocytopenia. Antinuclear antibody (ANA) induction is possible.
Fetal Monitoring

Warnings & precautions

■ FDA Black Box Warning

Procainamide can cause blood dyscrasias (e.g., agranulocytosis, neutropenia, thrombocytopenia) that may be fatal. Patients should have regular blood counts.

Side Effect Profile

Serious Effects

Absolute Contraindications

["Complete heart block (unless pacemaker placed)","Second-degree AV block","Systemic lupus erythematosus","Known hypersensitivity to procainamide or related drugs","Torsades de pointes or marked QT prolongation"]

Clinical Precautions

Precautions

["Lupus erythematosus-like syndrome (especially in slow acetylators)","QT prolongation and torsades de pointes","Hypotension","Bone marrow depression","Hepatotoxicity","Renal impairment requiring dose adjustment"]

Clinical Tips & Counseling

Drug interactions

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PROCAN SR

Clinical safety rating: caution

Comprehensive clinical and safety monograph for PROCAN SR (PROCAN SR).

How it works

Procainamide is a class Ia antiarrhythmic agent that blocks sodium channels, reducing myocardial excitability and conduction velocity, and prolonging the refractory period.

What the body does with it

Metabolism	Hepatic N-acetylation by N-acetyltransferase to N-acetylprocainamide (NAPA); NAPA undergoes further metabolism by CYP2D6 and other pathways.
Excretion	Renal: 50-60% as unchanged procainamide; hepatic metabolism to N-acetylprocainamide (NAPA) which is also renally excreted; total renal excretion of procainamide + NAPA accounts for ~85% of dose; remainder fecal (<5%).
Half-life	Procainamide: 2.5-4.7 hours (normal renal function); NAPA: 6-8 hours. In renal impairment, half-life prolonged up to 10-20 hours for procainamide and 40+ hours for NAPA.
Protein binding	Procainamide: 15-20% bound to plasma proteins (albumin and alpha-1 acid glycoprotein); NAPA: 10% bound.
Volume of Distribution	Procainamide: 2 L/kg (1.5-2.5 L/kg); distributes extensively into tissues, including heart, liver, and kidneys.
Bioavailability	Oral (immediate release): 75-95% (mean 83%); Oral (sustained-release): approximately 80-90% relative to immediate release.
Onset of Action	Oral (immediate release): 30-60 min; Oral (sustained-release): 1-2 hours; IV: immediate (within 1-2 minutes).
Duration of Action	Oral (immediate release): 3-4 hours; Oral (sustained-release): 6-8 hours; IV: 1-2 hours after bolus. Clinical effect correlates with therapeutic plasma concentration of 4-10 mcg/mL (procainamide + NAPA).

Classification & Brands

Dosing & administration

Oral: 50 mg/kg/day divided every 6 hours; typical adult dose: 250-500 mg every 6 hours. For sustained-release (Procan SR): 500-1000 mg every 6 hours.

Dosage form	TABLET, EXTENDED RELEASE
Renal impairment	GFR 30-50 mL/min: administer every 8-12 hours. GFR 15-29 mL/min: administer every 12-24 hours. GFR <15 mL/min: administer every 24-48 hours or avoid use.
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	Oral: 15-50 mg/kg/day divided every 3-6 hours; maximum 4 g/day. For sustained-release: not recommended in children <12 years.
Geriatric use	Start at lower end of dosing range (250 mg every 12 hours for sustained-release) and titrate slowly; monitor for hypotension, bradycardia, and QT prolongation due to reduced renal clearance and comorbidities.

Use during pregnancy

1st trimester	Consult provider
2nd trimester	Consult provider
3rd trimester	Consult provider

Clinical note

Comprehensive clinical and safety monograph for PROCAN SR (PROCAN SR).

Breastfeeding	Present in breast milk; M/P ratio approximately 0.2-0.3. Estimated infant dose <10% maternal weight-adjusted dose. Caution: Monitor infant for rash, agranulocytosis, tachycardia. Usually compatible with breastfeeding.
Teratogenic Risk	FDA Category C. First trimester: Procainamide crosses placenta; risk of fetal cardiac arrhythmias. Second/third trimesters: Potential for hypotension, reduced uterine blood flow, and neonatal thrombocytopenia. Antinuclear antibody (ANA) induction is possible.
Fetal Monitoring

Warnings & precautions

■ FDA Black Box Warning

Procainamide can cause blood dyscrasias (e.g., agranulocytosis, neutropenia, thrombocytopenia) that may be fatal. Patients should have regular blood counts.