- See: 
- Class I Agents 
- Discussion: 
- for prevention of PAT, atrial fibrillation, ventricular tachycardia, PVCs; 
- acts by depressing automaticity and conduction of the myocardium; 
- Class I antiarrhythmic; 
- Adult: PAC, PVC: 
- 200-300 mg PO tid-qid;

- PAT: 400-600 mg PO q2-3hr until terminated; 
- Conversion of atrial fibrillation or flutter: 
- use after digitalization: 200 mg q 2-3hr for 8 doses; 
- then increase daily dose to maximum of 3-4 gm or until normal rhythm; 
- follow serum levels if possible; 
- Precautions: 
- Quinidine will produce doubling of Digitalis plasma level; 
- Digitalization is indicated before starting quinidine in order to block AV nodal conduction; 
- if quinidine is used before digitization, it may increase AV nodal conduction and ventricular rate; 
- Contraindications: 
- Complete AV block; 
- Digitalis intoxication 
- Complete bundle branch block