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Case Reports
. 2023 May 5;20(1):89.
doi: 10.1186/s12985-023-02058-3.

Switch from a ritonavir to a cobicistat containing antiretroviral regimen and impact on tacrolimus levels in a kidney transplant recipient

Andrea Erba  1 , Catia Marzolini  2   3 , Katharina Rentsch  4 , Marcel Stoeckle  2 , Manuel Battegay  2 , Michael Mayr #  5 , Maja Weisser #  2
Affiliations
Case Reports

Switch from a ritonavir to a cobicistat containing antiretroviral regimen and impact on tacrolimus levels in a kidney transplant recipient

Andrea Erba et al. Virol J. .

Abstract

Background: Solid-organ transplantation due to end-stage organ disease is increasingly performed in people living with HIV. Despite improved transplant outcomes, management of these patients remains challenging due to higher risk for allograft rejection, infection and drug-drug interactions (DDIs). Complex regimens for multi-drug resistant HIV-viruses may cause DDIs particularly if the regimen contains drugs such as ritonavir or cobicistat.

Case presentation: Here we report on a case of an HIV-infected renal transplant recipient on long-term immunosuppressive therapy with mycophenolate mofetil and tacrolimus dosed at 0.5 mg every 11 days due to the co-administration of a darunavir/ritonavir containing antiretroviral regimen. In the presented case the pharmacokinetic booster was switched from ritonavir to cobicistat for treatment simplification. A close monitoring of tacrolimus drug levels was performed in order to prevent possible sub- or supratherapeutic tacrolimus trough levels. A progressive decrease in tacrolimus concentrations was observed after switch requiring shortening of tacrolimus dosing interval. This observation was unexpected considering that cobicistat is devoid of inducing properties.

Conclusions: This case highlights the fact that the pharmacokinetic boosters ritonavir and cobicistat are not fully interchangeable. Therapeutic drug monitoring of tacrolimus is warranted to maintain levels within the therapeutic range.

Keywords: Cobicistat; Drug–drug interaction; HIV; Kidney transplantation; Pharmacokinetic booster; Ritonavir.

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Conflict of interest statement

This manuscript has not been published and is not under consideration for publication elsewhere. We have no conflicts of interest to disclose.

Figures

Fig. 1
Fig. 1
Tacrolimus profiles during ritonavir-boosted and cobicistat-boosted antiretroviral regimens. Three 11 days pharmacokinetic tacrolimus concentrations profiles in blue while on the ritonavir-boosted regimen before the switch and in red while on the cobicistat-boosted regimen after the switch. *For practical reasons (weekend, holidays) tacrolimus trough levels were measured on day 9 at the end of the third pharmacokinetic profile and on day 10 at the end of the sixth pharmacokinetic profile
Fig. 2
Fig. 2
Antiretroviral treatment and tacrolimus trough levels before and after therapy switch. Blue bars indicate drugs before switch and blue dots tacrolimus levels before switch. Red bars indicate drugs after switch and red dots indicate tacrolimus trough levels after switch. Tacrolimus dosing interval was shortened from 11 to 9 days due to sub-therapeutic through levels*
See this image and copyright information in PMC

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