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Bupropion plasma levels and CYP2D6 phenotype
B G Pollock1, R A Sweet, M Kirshner
1Department of Psychiatry, University of Pittsburgh School of Medicine, Pennsylvania, USA.
Therapeutic Drug Monitoring
|October 1, 1996
Summary
Bupropion does not interact with the CYP2D6 enzyme, unlike most antidepressants. However, a metabolite, hydroxybupropion, may accumulate in poor metabolizers, potentially affecting safety and efficacy.
Area of Science:
- Pharmacology
- Drug Metabolism
- Clinical Pharmacy
Background:
- Most available antidepressants interact with the cytochrome P450 2D6 (CYP2D6) enzyme, either through metabolism or inhibition.
- The interaction of bupropion with CYP2D6 has not been previously investigated.
Purpose of the Study:
- To investigate whether bupropion is metabolized by or inhibits the CYP2D6 enzyme.
- To assess the potential impact of CYP2D6 metabolic status on bupropion and its metabolite plasma levels.
Main Methods:
- Studied 12 patients, including three CYP2D6 poor metabolizers, assessing plasma levels of bupropion and its metabolites.
- Utilized debrisoquine metabolic status as a probe for CYP2D6 activity.
- Re-phenotyped three patients during bupropion treatment to assess any induced changes in metabolic ratios.
Main Results:
- Plasma level/dose ratios for bupropion and its erythrohydrobupropion and threohydrobupropion metabolites were not associated with CYP2D6 metabolic status.
- Plasma level/dose ratios for the hydroxybupropion metabolite were significantly higher in poor CYP2D6 metabolizers.
- Bupropion treatment did not alter debrisoquine metabolic ratios in patients, indicating no inhibition or induction of CYP2D6.
Conclusions:
- Bupropion is neither metabolized by nor inhibits the CYP2D6 enzyme.
- The accumulation of hydroxybupropion in poor CYP2D6 metabolizers could potentially contribute to bupropion toxicity and reduced therapeutic effectiveness.