Bupropion immediate-release

7 DRUG INTERACTIONS CYP2B6 inducers: Dose increase may be necessary if coadministered with CYP2B6 inducers (e.g., ritonavir, lopinavir, efavirenz, carbamazepine, phenobarbital, and phenytoin) based on clinical response, but should not exceed the maximum recommended dose. ( 7.1 ) Drugs metabolized by CYP2D6: Bupropion inhibits CYP2D6 and can increase concentrations of: antidepressants (e.g., venlafaxine, nortriptyline, imipramine, desipramine, paroxetine, fluoxetine, sertraline), antipsychotics (e.g., haloperidol, risperidone, thioridazine), beta-blockers (e.g., metoprolol), and Type 1C antiarrhythmics (e.g., propafenone, flecainide). Consider dose reduction when using with bupropion.

(7.2 ) Digoxin: May decrease plasma digoxin levels. Monitor digoxin levels. ( 7.2 ) Drugs that lower seizure threshold: Dose bupropion hydrochloride tablets with caution. ( 5.3 , 7.3 ) Dopaminergic drugs (levodopa and amantadine): CNS toxicity can occur when used concomitantly with bupropion hydrochloride tablets. ( 7.4 ) MAOIs: Increased risk of hypertensive reactions can occur when used concomitantly with bupropion hydrochloride tablets. ( 7.6 ) Drug-laboratory test interactions: Bupropion hydrochloride tablets can cause false-positive urine test results for amphetamines. ( 7.7 )

7.1 Potential for Other Drugs to Affect Bupropion Hydrochloride Tablets Bupropion is primarily metabolized to hydroxybupropion by CYP2B6. Therefore, the potential exists for drug interactions between bupropion hydrochloride tablets and drugs that are inhibitors or inducers of CYP2B6. Inhibitors of CYP2B6 Ticlopidine and Clopidogrel : Concomitant treatment with these drugs can increase bupropion exposure but decrease hydroxybupropion exposure. Based on clinical response, dosage adjustment of bupropion hydrochloride tablets may be necessary when coadministered with CYP2B6 inhibitors (e.g., ticlopidine or clopidogrel) [see Clinical Pharmacology ( 12.3 )].

Inducers of CYP2B6 Ritonavir, Lopinavir, and Efavirenz : Concomitant treatment with these drugs can decrease bupropion and hydroxybupropion exposure. Dosage increase of bupropion hydrochloride tablets may be necessary when coadministered with ritonavir, lopinavir, or efavirenz [see Clinical Pharmacology ( 12.3 )] but should not exceed the maximum recommended dose. Carbamazepine, Phenobarbital, Phenytoin: While not systematically studied, these drugs may induce the metabolism of bupropion and may decrease bupropion exposure [see Clinical Pharmacology ( 12.3 )] .

If bupropion is used concomitantly with a CYP inducer, it may be necessary to increase the dose of bupropion, but the maximum recommended dose should not be exceeded.

7.2 Potential for Bupropion Hydrochloride Tablets to Affect Other Drugs Drugs Metabolized by CYP2D6 Bupropion and its metabolites (erythrohydrobupropion, threohydrobupropion, hydroxybupropion) are CYP2D6 inhibitors. Therefore, coadministration of bupropion hydrochloride tablets with drugs that are metabolized by CYP2D6 can increase the exposures of drugs that are substrates of CYP2D6. Such drugs include certain antidepressants (e.g., venlafaxine, nortriptyline, imipramine, desipramine, paroxetine, fluoxetine, and sertraline), antipsychotics (e.g., haloperidol, risperidone, thioridazine), beta-blockers (e.g., metoprolol), and Type 1C antiarrhythmics (e.g., propafenone and flecainide).

When used concomitantly with bupropion hydrochloride tablets, it may be necessary to decrease the dose of these CYP2D6 substrates, particularly for drugs with a narrow therapeutic index. Drugs that require metabolic activation by CYP2D6 to be effective (e.g., tamoxifen) theoretically could have reduced efficacy when administered concomitantly with inhibitors of CYP2D6 such as bupropion. Patients treated concomitantly with bupropion hydrochloride tablets and such drugs may require increased doses of the drug [see Clinical Pharmacology ( 12.3 )]. Digoxin Coadministration of bupropion hydrochloride with digoxin may decrease plasma digoxin levels.

Monitor plasma digoxin levels in patients treated concomitantly with bupropion hydrochloride and digoxin [see Clinical Pharmacology ( 12.3 )] .

7.3 Drugs that Lower Seizure Threshold Use extreme caution when coadministering bupropion hydrochloride tablets with other drugs that lower seizure threshold (e.g., other bupropion products, antipsychotics, antidepressants, theophylline, or systemic corticosteroids). Use low initial doses and increase the dose gradually [see Contraindications ( 4 ), Warnings and Precautions ( 5.3 )] .

7.4 Dopaminergic Drugs (Levodopa and Amantadine) Bupropion, levodopa, and amantadine have dopamine agonist effects. CNS toxicity has been reported when bupropion was coadministered with levodopa or amantadine. Adverse reactions have included restlessness, agitation, tremor, ataxia, gait disturbance, vertigo, and dizziness. It is presumed that the toxicity results from cumulative dopamine agonist effects. Use caution when administering bupropion hydrochloride tablets concomitantly with these drugs.

7.5 Use with Alcohol In postmarketing experience, there have been rare reports of adverse neuropsychiatric events or reduced alcohol tolerance in patients who were drinking alcohol during treatment with bupropion hydrochloride tablets. The consumption of alcohol during treatment with bupropion hydrochloride tablets should be minimized or avoided.

7.6 MAO Inhibitors Bupropion inhibits the reuptake of dopamine and norepinephrine. Concomitant use of MAOIs and bupropion is contraindicated because there is an increased risk of hypertensive reactions if bupropion is used concomitantly with MAOIs. Studies in animals demonstrate that the acute toxicity of bupropion is enhanced by the MAO inhibitor phenelzine. At least 14 days should elapse between discontinuation of an MAOI intended to treat depression and initiation of treatment with bupropion hydrochloride tablets.

Conversely, at least 14 days should be allowed after stopping bupropion hydrochloride tablets before starting an MAOI antidepressant [see Dosage and Administration (2.4 , 2.5 ), Contraindications ( 4 )] .

7.7 Drug-Laboratory Test Interactions False-positive urine immunoassay screening tests for amphetamines have been reported in patients taking bupropion. This is due to lack of specificity of some screening tests. False-positive test results may result even following discontinuation of bupropion therapy. Confirmatory tests, such as gas chromatography/mass spectrometry, will distinguish bupropion from amphetamines.