Paroxetineinteractions

No drug-drug interaction studies have been conducted with paroxetine capsules. Paroxetine is a strong CYP2D6 inhibitor. Co-administration of paroxetine capsules can alter concentrations of other drugs that are metabolized by CYP2D6. Consider potential drug interactions prior to and during therapy. See Full Prescribing Information for a list of clinically significant drug interactions

7.1 Potential for

Paroxetine Capsules to Affect Other Drugs Paroxetine is a strong CYP2D6 inhibitor. Clinical drug interaction studies have been performed with substrates of CYP2D6 and show that paroxetine can inhibit the metabolism of drugs metabolized by CYP2D6. Table 2 contains examples of drugs with a metabolism that may be affected by co-administration with paroxetine capsules. Table 2 Effects of Paroxetine on Other Drugs Concomitant Drug Name Effect of Paroxetine on Other Drugs Clinical Recommendations Thioridazine Increased plasma concentrations of thioridazine Potential QTc prolongation Concomitant use of thioridazine and paroxetine capsules is contraindicated. Pimozide Increased plasma concentrations of pimozide. Potential QTc prolongation Concomitant use of pimozide and paroxetine capsules is contraindicated. Tamoxifen Reduced plasma concentrations of active tamoxifen metabolite Consider avoiding concomitant use of tamoxifen and paroxetine capsules. Tricyclic Antidepressants (TCA) (e.g., Desipramine) Increased plasma concentrations and elimination half-life Plasma TCA concentrations may need to be monitored and the dose of TCA may need to be reduced if a TCA is co-administered with paroxetine capsules. Monitor tolerability. Risperidone Increased plasma concentrations of risperidone A lower dosage of risperidone may be necessary (see the Full Prescribing Information for risperidone). Monitor tolerability. Atomoxetine Increased exposure of atomoxetine A lower dosage of atomoxetine may be necessary (see Full Prescribing Information for atomoxetine). Monitor tolerability. Drugs Highly Bound to Plasma Protein (e.g., Warfarin) Increased free plasma concentrations The dosage of warfarin may need to be reduced. Monitor tolerability and the International Normalized Ratio. Digoxin Decreased plasma concentrations of digoxin Dosage of digoxin may need to be increased. Monitor digoxin concentrations and clinical effect. Theophylline Increased plasma concentrations of theophylline Dosage of theophylline may need to be decreased. Monitor theophylline concentrations and tolerability. Use caution if co-administering paroxetine capsules with other drugs that are metabolized by CYP2D6, including nortriptyline, amitriptyline, imipramine, desipramine, fluoxetine, phenothiazines, risperidone, and Type 1C antiarrhythmics (e.g., propafenone, flecainide, and encainide).

7.2 Potential for

Other Drugs to Affect Paroxetine Capsules The metabolism and pharmacokinetics of paroxetine may be affected by the induction and inhibition of drug metabolizing enzymes such as CYP2D6. Table 3 contains a list of drugs that may affect the pharmacokinetics of paroxetine capsules when administered concomitantly. Table 3 Effects of Other Drugs on Paroxetine Concomitant Drug Name Effect of Concomitant Drug on Paroxetine Clinical Recommendations Phenobarbital Decreased paroxetine exposure No dose adjustment for paroxetine capsules. Monitor clinical effect of paroxetine capsules. Phenytoin Decreased paroxetine exposure Fosamprenavir/Ritonavir Decreased plasma concentration of paroxetine Cimetidine Increased plasma concentration of paroxetine Use caution if co-administering paroxetine capsules with other drugs that inhibit CYP2D6 (e.g., quinidine).

7.3 Other Potentially

Significant Drug Interactions Monoamine Oxidase Inhibitors (MAOIs) Serious adverse reactions such as serotonin syndrome have been reported in patients receiving a concomitant SSRI and MAOI, in patients started on an SSRI who recently received an MAOI and in patients started on an MAOI who recently received an SSRI. Therefore, concomitant use of MAOIs with paroxetine capsules or use of paroxetine capsules and an MAOI within 14 days of each other is contraindicated. Serotonergic Drugs If concomitant use of paroxetine capsules with other serotonergic drugs (e.g., other SNRIs, SSRIs, triptans, tricyclic antidepressants, opioids, lithium, tryptophan, buspirone, amphetamines, and St. John’s Wort) is clinically warranted, consider the increased risk of serotonin syndrome and carefully observe the patient, particularly during treatment initiation. An interaction between paroxetine and tryptophan may occur when they are co-administered. Adverse experiences, consisting primarily of headache, nausea, sweating, and dizziness, have been reported when tryptophan was administered to patients taking paroxetine. Consequently, concomitant use of paroxetine capsules with tryptophan is not recommended. Drugs that Interfere with Hemostasis (e.g., NSAIDs, Aspirin, and Warfarin) Altered anticoagulant effects, including increased bleeding, have been reported when SSRIs are co-administered with NSAIDs, aspirin, and warfarin or other drugs that affect coagulation. There may be a pharmacodynamic interaction between paroxetine and warfarin that causes an increased bleeding diathesis despite unaltered prothrombin time. Carefully monitor patients receiving warfarin therapy when paroxetine capsules is initiated or discontinued.