Indications
Propafenone is indicated for the treatment of paroxysmal atrial fibrillation/flutter (PAF), paroxysmal supraventricular tachycardia (PSVT). Propafenone is also indicated for the treatment of documented ventricular arrhythmias.
Pharmacology
Propafenone works by slowing the influx of sodium ions into the cardiac muscle cells, causing a decrease in excitability of the cells. Propafenone is more selective for cells with a high rate, but also blocks normal cells more than class Ia or Ib. Propafenone differs from the prototypical class Ic antiarrhythmic in that it has additional activity as a beta-adrenergic blocker which can cause bradycardia and bronchospasm.
Dosage & Administration
The dose of Propafenone must be individually titrated on the basis of response and tolerance. It is recommended that therapy be initiated with Propafenone 150 mg given every eight hours (450 mg/day). Dosage may be increased at a minimum of 3 to 4 day intervals to 225 mg every 8 hours (675 mg/day) and if necessary, to 300 mg every 8 hours (900 mg/day). The usefulness and safety of dosages exceeding 900 mg per day have not been established.
Interaction
Propafenone is metabolized by CYP2D6 (major pathway) and CYP1A2 and CYP3A4. Drugs that inhibit CYP2D6 (such as desipramine, paroxetine, ritonavir, sertraline), CYP1A2 (such as amiodarone) and CYP3A4 (such as ketoconazole, ritonavir, saquinavir, erythromycin and grapefruit juice) can be expected to cause increased plasma levels of propafenone. In addition, propafenone is an inhibitor of CYP2D6. Coadministration of propafenone with drugs metabolized by CYP2D6 (such as desipramine, imipramine, haloperidol, venlafaxine) might lead to increase plasma concentrations of these drugs.
Contraindications
Propafenone is contraindicated in the presence of uncontrolled congestive heart failure, cardiogenic shock, sinoatrial, atrioventricular and intraventricular disorders of impulse generation and/or conduction (e.g. sick sinus node syndrome, atrioventricular block) in the absence of an artificial pacemaker, bradycardia, marked hypotension, bronchospastic disorders, manifest electrolyte imbalance and known hypersensitivity to the drug.
Side Effects
Adverse reactions associated with propafenone occur most frequently in the gastrointestinal, cardiovascular and central nervous systems. Change in taste, constipation, diarrhea, dizziness, drowsiness, dry mouth, gas, headache, light-headedness, nausea, tiredness etc. may happen. Severe allergic reactions also reported with propafenone.
Pregnancy & Lactation
Pregnancy: Propafenone has been assigned to pregnancy category C by the FDA. There are no controlled data in human pregnancy. Limited data indicate that propafenone has been administered during the third trimester of pregnancy without adverse maternal or fetal effects. Propafenone should be given during pregnancy only when benefit outweighs risk.
Nursing Mothers: It is not known whether this drug is excreted in human milk. Because many drugs are excreted in human milk and because of the potential for serious adverse reactions in nursing infants from propafenone, a decision should be made whether to discontinue nursing or to discontinue the drug, taking into account the importance of the drug to the mother.
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