Dextromethorphan/Bupropion: Pharmacology, Indications, Dosing Guidelines and Adverse Effects

Dextromethorphan/bupropion is an oral medication that pairs an NMDA receptor antagonist and σ-1 agonist (dextromethorphan) with a CYP2D6-inhibiting NDRI (bupropion). Bupropion's inhibition of CYP2D6 increases dextromethorphan's bioavailability and extends its half-life roughly threefold. The drug has two FDA-approved indications: major depressive disorder, where it shows rapid antidepressant effects by week 1, and agitation associated with Alzheimer's disease dementia, where it is the first non-antipsychotic option. Absolute contraindications include seizure disorder, current or prior eating disorder, abrupt discontinuation of alcohol/benzodiazepines/barbiturates/antiepileptics, and concurrent or recent MAOI use.

Study at a glance

Abstract

After completing this activity, participants should be able to: 1. Describe the pharmacological mechanism of dextromethorphan/bupropion as an oral NMDA receptor antagonist and σ-1 agonist paired with a CYP2D6-inhibiting NDRI, explain how bupropion's CYP2D6 inhibition enhances dextromethorphan's bioavailability and extends its half-life ~3-fold, and identify its two FDA-approved indications — major depressive disorder (with rapid antidepressant effect by week 1) and agitation associated with dementia due to Alzheimer's disease (the first non-antipsychotic option for this indication). 2. Recognize absolute contraindications for dextromethorphan/bupropion (seizure disorder, current or prior eating disorder, abrupt discontinuation of alcohol/benzodiazepines/barbiturates/antiepileptics, concurrent or recent MAOI use) and apply the indication-specific titration schedules — the MDD schedule (45/105 mg once daily, advancing to twice daily after 3 days) and the slower Alzheimer's-agitation schedule using the new 30/105 mg tablet (30/105 mg once daily for week 1, twice daily on day 8, advancing to 45/105 mg twice daily on day 15) — along with dose adjustments for strong CYP2D6 inhibitors, known CYP2D6 poor metabolizers, and moderate renal impairment. 3. Evaluate the risk-benefit profile of dextromethorphan/bupropion in clinical practice, including assessment of abuse potential (dextromethorphan misuse, bupropion stimulant-like effects), management of indication-specific common adverse effects, and monitoring requirements for severe adverse events including seizure, serotonin syndrome, activation of mania/hypomania, angle-closure glaucoma, and the newly added hyponatremia warning — with particular attention to geriatric patients in whom hyponatremia symptoms can mimic dementia progression.