Which beta‑blockers are not metabolized by CYP2D6 and can be safely used in a CYP2D6 intermediate metabolizer (*41/*41) who is taking bupropion, a strong CYP2D6 inhibitor?

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Last updated: August 10, 2026 • View editorial policy

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Beta-Blockers Not Metabolized by CYP2D6

**For a CYP2D6 intermediate metabolizer (41/41) taking bupropion, the safest beta-blockers are those that do not rely on CYP2D6 metabolism: atenolol, nadolol, bisoprolol, labetalol, carvedilol, sotalol, and nebivolol.

CYP2D6-Independent Beta-Blockers

Based on the 2017 ACC/AHA hypertension guidelines 1, 2, 3, 4, 5, the following beta-blockers do not use the CYP2D6 pathway:

Renally Eliminated (No CYP2D6 Involvement)

  • Atenolol (25-100 mg daily, divided twice daily) - cardioselective
  • Nadolol (40-120 mg once daily) - non-cardioselective
  • Sotalol (40-160 mg twice daily) - also has Class III antiarrhythmic properties; renally excreted 6

Primarily Non-CYP2D6 Metabolism

  • Bisoprolol (2.5-10 mg once daily) - cardioselective; preferred in heart failure with reduced ejection fraction 1, 2, 4
  • Labetalol (200-800 mg twice daily) - combined alpha- and beta-receptor blocker
  • Carvedilol (12.5-50 mg twice daily) - combined alpha- and beta-receptor blocker; preferred in heart failure 1, 2, 4
  • Nebivolol (5-40 mg once daily) - cardioselective with vasodilatory properties via nitric oxide 1, 2, 4

Beta-Blockers That ARE Metabolized by CYP2D6 (AVOID)

The following beta-blockers must be avoided or require significant dose reduction in your patient:

  • Metoprolol (both tartrate and succinate) - extensively metabolized by CYP2D6 6
  • Propranolol - metabolized by CYP2D6
  • Carvedilol - has some CYP2D6 involvement (though less than metoprolol)
  • Timolol - CYP2D6 substrate

Critical Drug Interaction Context

Bupropion is a strong CYP2D6 inhibitor 7. The FDA label explicitly states: "Bupropion and its metabolites (erythrohydrobupropion, threohydrobupropion, hydroxybupropion) are CYP2D6 inhibitors. Therefore, coadministration of bupropion with drugs that are metabolized by CYP2D6 can increase the exposures of drugs that are substrates of CYP2D6. Such drugs include...beta-blockers (e.g., metoprolol)" 7.

Recent research confirms that bupropion's metabolites, particularly erythrohydrobupropion and threohydrobupropion, are the primary mediators of CYP2D6 inhibition, with inhibition potencies 5.5- to 13-fold greater than bupropion itself 8. This creates a double jeopardy scenario in your patient:

  1. Genetic impairment: CYP2D6 *41/*41 genotype = intermediate metabolizer status (reduced enzyme activity)
  2. Pharmacologic inhibition: Bupropion further blocks the already compromised CYP2D6 enzyme

Clinical Implications

If metoprolol or other CYP2D6-dependent beta-blockers were used in this patient, expect:

  • Dramatically increased beta-blocker exposure (up to 2-5 fold increase in AUC) 9, 10
  • Excessive bradycardia and hypotension risk
  • Prolonged drug effects due to reduced clearance

The 2024 CPIC guideline specifically addresses CYP2D6 poor metabolizers and metoprolol, recommending alternative beta-blockers or significant dose reductions 10. Your patient's intermediate metabolizer status combined with strong CYP2D6 inhibition from bupropion functionally creates a "phenoconverted poor metabolizer" scenario.

Recommended Approach

First-line choices for this patient:

  1. Bisoprolol - if heart failure indication (preferred in HFrEF)
  2. Atenolol - if hypertension without heart failure
  3. Carvedilol - if heart failure indication (though has minor CYP2D6 involvement, still safer than metoprolol)

Avoid entirely: Metoprolol, propranolol, and timolol in this patient taking bupropion with CYP2D6 *41/*41 genotype.

References

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