Interaksi Propafenon dan Venlafaksin

• Avoid use with other antiarrhythmic agents or drugs that prolong the QT interval.

It may also worsen premature ventricular contractions or supraventricular arrhythmias, and it may prolong the QT interval.

Use with Drugs that Prolong the QT Interval and Antiarrhythmic Agents The use of propafenone hydrochloride extended-release capsules in conjunction with other drugs that prolong the QT interval has not been extensively studied.

Such drugs may include many antiarrhythmics, some phenothiazines, tricyclic antidepressants, and oral macrolides.

Therefore, the potential exists for a drug interaction between drugs that inhibit CYP2D6-mediated metabolism of venlafaxine, reducing the metabolism of venlafaxine to ODV, resulting in increased plasma concentrations of venlafaxine and decreased concentrations of the active metabolite.

Drugs that Inhibit Cytochrome P450 Isoenzymes CYP2D6 Inhibitors: In vitro and in vivo studies indicate that venlafaxine is metabolized to its active metabolite, ODV, by CYP2D6, the isoenzyme that is responsible for the genetic polymorphism seen in the metabolism of many antidepressants.

CYP2D6 inhibitors such as quinidine would be expected to do this, but the effect would be similar to what is seen in patients who are genetically CYP2D6 poor metabolizers [see Clinical Pharmacology ( 12.3 )] .

Drugs Metabolized by Cytochrome P450 Isoenzymes CYP2D6 In vitro studies indicate that venlafaxine is a relatively weak inhibitor of CYP2D6.

Therefore, no dosage adjustment is required when venlafaxine is coadministered with a CYP2D6 inhibitor.