https://interactions.guidetherapeutiquevih.com/en/interaction-details?id=15552

Atazanavir / cobicistat

Rifabutin

Avoid association.

No pharmaceutical opinion available for this interaction.

Mechanism

Atazanavir / cobicistat can inhibit the metabolism (CYP 3A4) and increase the plasma concentration of Rifabutin.

Rifabutin can induce the metabolism (CYP 3A4) and decrease the plasma concentration of Atazanavir / cobicistat.

Atazanavir / cobicistat

Pharmacodynamic effects

Possible decrease of clinical efficacy.

Risk of a possible development of resistance to antiretroviral class.

Recommendations

Association not recommended. If used, closely monitor clinical effectiveness.

Choose an alternative.

Alternative solution(s)

Protease inhibitor boosted with ritonavir or

Rifabutin

Pharmacodynamic effects

Possible increase of adverse effects.

Recommendations

Avoid this combination, otherwise a decrease in the dose is necessary.

Dose reduction suggested of up to 75% (e.g., 150 mg every other day).

To increase the probabilities of achieving therapeutic serum levels and reduce the development of resistance and treatment failures some experts, as well as the DHHS, recommend a rifabutin dose of 150mg QD.

Monitor closely clinical efficacy and appearance of adverse effects.

Alternative solution(s)

–

Monitor

Rifabutin adverse effects : rash, taste alterations, anorexia, nausea, insomnia, facial paralysis, twitching, peripheral neuritis, neutropenia, thrombocytopenia, arthralgia, uveitis, elevation of liver function tests.

Tests

Rifabutin

Blood count

Liver function

CD4+

Viral load HIV

Atazanavir plasma level

Pharmacokinetic parameters

–

Comment

Several studies were initially done with healthy subjects with the combination of protease inhibitors and rifabutin. These studies demonstrated that a dose of rifabutin 150 mg 3 times/week associated with protease inhibitors was approximately equivalent to a dose of rifabutin 300 mg QD.
Subsequently, studies in subjects co-infected with HIV and tuberculosis demonstrated that the dose of 150 mg 3 times/week was insufficient for some subjects. Therefore, the dose of rifabutin 150 mg QD in combination with PIs is currently recommended in the guidelines.

Ref #3117 : To optimize the monitoring for rifabutin, dosage of this agent, at equilibrium (t1/2 normal; 25hrs), may be necessary. The targeted therapeutic index of 0.3-0.9μg/ml 3-4 post dose (Cmax) and a dose reduction may be necessary from 1 μg/ml depending on the clinical context.

Reference
  • 3230
    Atazanavir/cobicistat (Evotaz), Bristol-Myers Squibb, Québec, Canada, 8 septembre 2017.
  • 3117
    Regazzi M, Carvalho AC, Villani P, Matteelli A. Treatment Optimization in Patients Co-Infected with HIV and Mycobacterium tuberculosis Infections: Focus on Drug–Drug Interactions with Rifamycins. Clinical Pharmacokinetics, June 2014, 53 (6), 489-507.
  • 1096
    Rifabutin (Mycobutin), Pfizer, Québec, Canada, 22 juin 2015.
  • 3151
    U.S. Department of Health and Human services (DHHS) : Guidelines for the Use of Antiretroviral Agents in Adults and Adolescents Living with HIV. Disponible : https://clinicalinfo.hiv.gov/en/guidelines/adult-and-adolescent-arv/whats-new-guidelines. Publié le 16 août 2021. Consulté le 16 septembre 2021.
  • 3116
    Center for Disease Control and prevention. Managing Drug Interactions in the Treatment of HIV-Related Tuberculosis. Disponible: http://www.cdc.gov/tb/publications/guidelines/tb_hiv_drugs/recommendations03.htm Publié le 22 sept 2014. Consulté le 11 janvier 2018.
  • 2449
    Naiker S, Conolly C, Weisner L, Kellerman T, Reddy T et al.Randomized pharmacokinetic evaluation of different rifabutin doses in African HIV- infected tuberculosis patients on lopinavir/ritonavir-based antiretroviral therapy. BMC Pharmacol Toxicol. 2014; 15: 61.