Amiodarone and Venlafaxine interaction

Reserve the combination of amiodarone with other antiarrhythmic therapies that prolong the QTc to patients with life-threatening ventricular arrhythmias who are incompletely responsive to a single agent.

Table 5: Amiodarone Drug Interactions Concomitant Drug Class/Name Examples Clinical Comment QT Prolonging Drugs class I and III antiarrhythmics, lithium, certain phenothiazines, tricyclic antidepressants, certain fluoroquinolone and macrolide antibiotics, azole antifungals, halogenated inhalation anesthetic agents Increased risk of Torsade de Pointes.

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.

Concomitant use of CYP3A4 inhibitors and venlafaxine may increase levels of venlafaxine and ODV.

Therefore, caution is advised if a patient’s therapy includes a CYP3A4 inhibitor and venlafaxine concomitantly.

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 )] .