What If… Patient Wants to Take Zyban (bupropion)?

• Buproprion is a substrate of CYP2B6:

  • in vitro data show that ritonavir, efavirenz, and nelfinavir can inhibit CYP2B6

• Although the amount of ritonavir contained in Kaletra formulation is relatively low, still potential for interaction

• Use combination with caution, monitor for buproprion toxicity, may need to ? dose

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• Many antidepressants have narrow therapeutic windows, so careful attention to dosing is required.

• Many agents in this class are primarily substrates of CYP2D6
  • e.g., TCAs: amitriptyline, nortriptyline, desipramine, imipramine
  • e.g., SSRIs: fluoxetine, fluvoxamine, paroxetine

• However, bupropion is a substrate of CYP2B6

• In vitro experiments have shown that ritonavir, efavirenz, and nelfinavir can inhibit CYP2B6; therefore, the potential exists for interactions with bupropion. Indinavir, saquinavir and amprenavir were only weakly inhibitory of bupropion; hence no or only minor increase in bupropion levels anticipated.
  • Hesse LM, von Moltke LL, Shader RI, Greenblatt DJ. Ritonavir, efavirenz, and nelfinavir inhibit CYP2B6 activity in vitro: potential drug interactions with bupropion. Drug Metab Dispos 2001;29:100-102

• Similar caution should be used when giving bupropion with lopinavir/ritonavir.