Drug General Information (ID: DDIUIYRG3O)
Drug Name			Quinidine		Drug Info		Propafenone		Drug Info
Drug Type		Small molecule				Small molecule
Therapeutic Class		Group I Antiarrhythmics				Antiarrhythmic Agents
Structure

Mechanism of Quinidine-Propafenone Interaction (Severity Level: Major)
Increased risk of prolong QT interval Click to Show/Hide Mechanism Graph
Drug Name		Quinidine				Propafenone
Mechanism		Prolong QT interval				Prolong QT interval
Key Mechanism Factor 1
		Factor Name		QT interval
		Factor Description		Long QT syndrome is a heart signaling disorder that can cause a fast, chaotic heartbeat (arrhythmia). Many people may not exhibit symptoms, and usually the condition is detected during routine medical tests. In others, the most common symptoms include: sudden fainting, palpitations, dizziness, seizures, sudden death.
Mechanism Description		Increased risk of prolong QT interval by the combination of Quinidine and Propafenone

Recommended Action
Management		Propafenone product labeling for the sustained-release formulation recommends that concomitant use with Class IA and III antiarrhythmic agents be avoided. In addition, these agents should be withheld for at least 5 half-lives prior to dosing with propafenone. Close monitoring of clinical response, ECG, and drug levels is recommended if concomitant use with quinidine is required, and the propafenone dosage adjusted accordingly. In one study, average propafenone dosages were reduced by 45%. Patients should be advised to promptly notify their physician if they experience nausea, vomiting, fatigue, visual disturbances, headache, irregular heartbeats, changes in pulse rate, chest pain, or dyspnoea during treatment.

References
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3	Hii JT, Wyse DG, Gillis AM, et al "Propafenone-induced torsade de pointes: cross-reactivity with quinidine." Pacing Clin Electrophysiol 14 (1991): 1568-70. [PMID: 1721143]
4	Klein RC, Huang SK, Marcus FI, et al "Enhanced antiarrhythmic efficacy of propafenone when used in combination with procainamide or quinidine." Am Heart J 114 (1987): 551-8. [PMID: 3630896]
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6	Product Information. Rhythmol (propafenone). Knoll Pharmaceutical Company, Whippany, NJ.
7	Product Information. Rythmol SR (propafenone). GlaxoSmithKline, Research Triangle Park, NC.
8	Siddoway LA, Thompson KA, McAllister CB, Wang T, Wilkinson GR, Roden DM, Woosley RL "Polymorphism of propafenone metabolism and disposition in man: clinical and pharmacokinetic consequences." Circulation 75 (1987): 785-91. [PMID: 3829342]
9	Zehender M, Hohnloser S, Geibel A, et al "Short-term and long-term treatment with propafenone: determinants of arrhythmia suppression, persistence of efficacy, arrhythmogenesis, and side effects in patients." Br Heart J 67 (1992): 491-7. [PMID: 1622701]