What If… Patient Requires MAC Prophylaxis?

• Rifabutin:

  • is a substrate and inducer of CYP3A4
  • lopinavir/r significantly ? concentrations of rifabutin and its metabolite: risk of toxicity
  • need to ? rifabutin dose by 75% (I.e., 150 mg 2-3 times/week)

• Consider using azithromycin which does not induce CYP3A4 enzymes

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With concomitant administration of rifabutin & lopinavir/ritonavir:

5-6-fold ? rifabutin + metabolite AUC; rifabutin 150 mg daily had no significant effect on lopinavir/r concentrations. Reduce rifabutin dosage by at least 75% (i.e., max. 150 mg q2d or 3 times/week); monitor for adverse events and further decrease rifabutin dose if necessary.

• Azithromycin 1250 mg once weekly is a suitable alternative to rifabutin for the indication of MAC prophylaxis. Azithromycin does not affect the cytochrome P450 system, and therefore should not affect lopinavir concentrations.