PROCAINAMIDE HYDROCHLORIDE
Clinical safety rating
safeAnimal studies have demonstrated safety
Animal studies have demonstrated safety
Treatment of life-threatening ventricular arrhythmiasAtrial fibrillationAtrial flutterParoxysmal supraventricular tachycardia
Lupus-like syndrome
Class Ia antiarrhythmic agent; blocks sodium channels, slowing conduction velocity and prolonging refractory period in atrial and ventricular myocardium.
| Metabolism | Hepatic acetylation via N-acetyltransferase (NAT2) to N-acetylprocainamide (NAPA); CYP2D6 minor pathway. |
| Excretion | Renal: ~50-60% unchanged via glomerular filtration and tubular secretion; hepatic metabolism to N-acetylprocainamide (NAPA, active) accounts for ~15-30% of dose, further eliminated renally; biliary/fecal: negligible (<5%). |
| Half-life | Terminal elimination half-life: 2.5-5 hours (normal renal function); prolonged to 11-20 hours in renal impairment (e.g., CrCl <30 mL/min); clinical context: requires dosing adjustment in renal failure; NAPA half-life: 6-8 hours (normal), up to 40 hours in renal failure. |
| Protein binding | ~15-20% bound to serum albumin and alpha-1-acid glycoprotein; low binding minimizes displacement interactions. |
| Volume of Distribution | Vd: 1.5-2.5 L/kg (total body water); extensive tissue distribution (e.g., heart, liver, kidneys); clinical meaning: large Vd indicates substantial extravascular distribution, requiring loading doses for rapid therapeutic effect. |
| Bioavailability | Oral: 75-95% (immediate-release); IM: 100%; sustained-release oral: ~90% (relative to immediate-release). |
| Onset of Action | IV: immediate (within 1-2 minutes); IM: 10-30 minutes; oral: 30-60 minutes (fasted state); peak effect oral: 1-2 hours. |
| Duration of Action | IV/IM: 3-4 hours (antiarrhythmic effect); oral immediate-release: 3-6 hours; sustained-release oral: 8-12 hours; clinical note: duration correlates with plasma concentration >4 mcg/mL. |
| Molecular Weight | 271.79 |
Oral: 250-500 mg every 3-6 hours. IV: Loading dose 15-18 mg/kg infused over 25-30 minutes, then maintenance infusion 1-4 mg/min. Maximum total daily dose: 4 g.
| Dosage form | CAPSULE |
| Renal impairment | CrCl 10-50 mL/min: administer every 6-12 hours. CrCl <10 mL/min: administer every 8-24 hours. For IV: reduce maintenance infusion rate proportional to CrCl. |
| Liver impairment | Child-Pugh Class A: no adjustment; Class B: reduce dose by 25-50%; Class C: avoid use or reduce dose by 50-75% with monitoring. |
| Pediatric use | Oral: 15-50 mg/kg/day divided every 3-6 hours. IV: Loading dose 15-18 mg/kg; maintenance 20-80 mcg/kg/min. Maximum: 100 mg/kg/day. |
| Geriatric use | Start with lower doses (e.g., 250 mg oral every 6 hours) due to age-related renal decline. Monitor for hypotension and toxicity. Adjust based on CrCl. |
| 1st trimester | Procainamide crosses the placenta. Limited human data; animal studies not fully adequate. Use only if clearly needed. Consider risk of drug-induced lupus in mother. |
| 2nd trimester | Procainamide crosses the placenta. No known teratogenicity specific to second trimester. Monitor maternal lupus-like reactions. Use if benefit outweighs risk. |
| 3rd trimester | Procainamide crosses the placenta. May cause maternal hypotension and placental insufficiency. Potential neonatal effects: bradycardia, QT prolongation, drug-induced lupus. Use cautiously. |
Clinical note
Other drugs that prolong the QT interval increase risk of torsades de pointes Can cause lupus-like syndrome and blood dyscrasias.
| Placental transfer | Procainamide crosses the placenta. Cord blood concentrations approximate maternal plasma levels. Active metabolite also crosses. |
| Breastfeeding | Procainamide and its active metabolite N-acetylprocainamide are excreted into breast milk in low concentrations, considered compatible with breastfeeding. Monitor infant for bradycardia, QT prolongation, and lupus-like symptoms. American Academy of Pediatrics rates as usually compatible. |
| Lactation Rating | L2 (Safer, but limited data) per Hale's lactation risk categories |
| Teratogenic Risk | FDA Pregnancy Category C. First trimester: Limited human data; animal studies suggest potential fetal harm. Second/third trimesters: May cause maternal hypotension reducing placental perfusion; use only if clearly needed. Risk of neonatal arrhythmias if used near term. |
| Fetal Monitoring | Monitor maternal blood pressure, heart rate, ECG, and serum procainamide and NAPA levels (therapeutic range 4-10 mcg/mL for procainamide). Assess fetal heart rate patterns during infusion. Monitor for maternal lupus-like syndrome. |
| Fertility Effects | No known direct effects on fertility. May indirectly affect gonadal function if autoimmune reactions occur. |
■ FDA Black Box Warning
May cause severe blood dyscrasias (e.g., agranulocytosis, neutropenia, thrombocytopenia) and drug-induced lupus erythematosus.
| Common Effects | Lupus-like syndrome |
| Serious Effects |
Complete heart blockSecond-degree AV block (unless pacemaker in place)Torsades de pointesSystemic lupus erythematosus (active or history)Known hypersensitivity to procainamide or any component
| Precautions | Monitor CBC regularly; discontinue if blood dyscrasias occur. Prolonged QT interval risk; caution with other QT-prolonging drugs. May exacerbate heart failure or hypotension. Reduce dose in renal impairment. |
| Food/Dietary | Avoid excessive intake of potassium-rich foods (e.g., bananas, oranges, tomatoes) as hyperkalemia may increase proarrhythmic risk. Alcohol may exacerbate hypotension and cardiac effects. |
| Clinical Pearls | Procainamide is a Class Ia antiarrhythmic. Monitor for lupus-like syndrome (arthralgias, rash) especially in slow acetylators; screen with ANA titer. Torsades de Pointes risk; monitor QTc. Maintain serum potassium >4.0 mEq/L. Avoid in myasthenia gravis. Adjust dose in renal impairment. |
| Patient Advice | Take exactly as prescribed; do not skip doses. · Report any joint pain, rash, fever, or unexplained bruising immediately. · Avoid driving if you experience dizziness or lightheadedness. · Notify your doctor if you have new or worsening shortness of breath or chest pain. · Do not stop taking abruptly; this may cause a serious irregular heartbeat. |
Loading safety data…