Pharmacokinetics and 48 week efficacy of adjusted dose indinavir/ritonavir in rifampicin-treated HIV/tuberculosis-coinfected patients: a pilot study

Comprehensive in vitro analysis evaluating the variable drug-drug interaction risk of rifampicin compared to rifabutin

Compared to rifampicin (600 mg/day), standard doses of rifabutin (300 mg/day) have a lower risk of drug-drug interactions due to induction of cytochrome P450 3A4 (CYP3A4) or P-glycoprotein (Pgp/ABCB1) mediated by the pregnane X receptor (PXR). However, clinical comparisons with equal rifamycin doses or in vitro experiments respecting actual intracellular concentrations are lacking. Thus, the genuine pharmacological differences and the potential molecular mechanisms of the discordant perpetrator effects are unknown. Consequently, the cellular uptake kinetics (mass spectrometry), PXR activation (luciferase reporter gene assays), and impact on CYP3A4 and Pgp/ABCB1 expression and activity (polymerase chain reaction, enzymatic assays, flow cytometry) were evaluated in LS180 cells after treatment with different rifampicin or rifabutin concentrations for variable exposure times and eventually normalized to actual intracellular concentrations. In addition, inhibitory effects on CYP3A4 and Pgp activities were investigated. While rifampicin is poorly taken up by LS180 cells, it strongly activates PXR and leads to enhanced expression and activity of CYP3A4 and Pgp. In contrast, rifabutin is a significantly less potent and less efficient PXR activator and gene inducer, despite sixfold to eightfold higher intracellular accumulation. Finally, rifabutin is a potent inhibitor of Pgp (IC50 = 0.3 µM) compared to rifampicin (IC50 = 12.9 µM). Together, rifampicin and rifabutin significantly differ by their effects on the regulation and function of CYP3A4 and Pgp, even when controlled for intracellular concentrations. Rifabutin's concurrent Pgp inhibitory action might partly compensate the inducing effects, explaining its weaker clinical perpetrator characteristics.

A Literature Review of Liver Function Test Elevations in Rifampin Drug-Drug Interaction Studies

Although rifampin drug–drug interaction (DDI) studies are routinely conducted, there have been instances of liver function test (LFT) elevations, warranting further evaluation. A literature review was conducted to identify studies in which combination with rifampin resulted in hepatic events and evaluate any similarities. Over 600 abstracts and manuscripts describing rifampin DDI studies were first evaluated, of which 30 clinical studies reported LFT elevations. Out of these, 11 studies included ritonavir in combination with other drug(s) in the rifampin DDI study. The number of subjects that were discontinued from treatment on these studies ranged from 0 to 71 (0–100% of subjects in each study). The number of subjects hospitalized for adverse events in these studies ranged from 0 to 41 (0–83.67% of subjects in each study). LFT elevations in greater than 50% of subjects were noted during the concomitant administration of rifampin with ritonavir‐boosted protease inhibitors and with lorlatinib; with labeled contraindication due to observed hepatotoxicity related safety findings only for saquinavir/ritonavir and lorlatinib. In the lorlatinib and ritonavir DDI studies, considerable LFT elevations were observed rapidly, typically within 24–72 h following co‐administration. A possible sequence effect has been speculated, where rifampin induction prior to administration of the combination may be associated with increased severity of the LFT elevations. The potential role of rifampin in the metabolic activation of certain drugs into metabolites with hepatic effects needs to be taken into consideration when conducting rifampin DDI studies, particularly those for which the metabolic profiles are not fully elucidated.

Co-medications and Drug-Drug Interactions in People Living with HIV in Turkey in the Era of Integrase Inhibitors

BACKGROUND

Long life expectancy in people living with human immunodeficiency virus (PLWH) caused an increase in comorbidities and co-medications. We aimed to analyse comedications and drug-drug interactions (DDIs) in antiretroviral therapy (ART)-naive PLWH in the era of integrase inhibitors.

METHODS

A retrospective observational study was conducted between January 2016-August 2019. Patients' characteristics and chronic co-medications were recorded. The University of Liverpool HIV drug interaction database was used for DDIs.

RESULTS

Among 745 patients, the chronic co-medication rate was 30.9%. Older age (p<0.001, OR:6.66, 95% CI: 3.86-11.49) and female gender (p=002, OR:2.25, 95%:1.14-4.44) were independently associated with co-medication. Cardiovascular system (CVS) and central nervous system (CNS) drugs were the most common co-medications. Older age patients (p<0.001, OR:12.04, 95% CI:4.63-36.71), having heterosexual (HS) contact (p=0.003, OR:3.8, 95% CI:1.57-9.22) were independently associated with CVS drugs use, while being men who have sex with men (MSM) (p=0.03, OR:2.59, 95% CI:1.11-6.03) were associated with CNS drugs use. DDIs were seen in 37.4% of patients with co-medications. Antidiabetics (23.3%), CNS (22.1%) and CVS drugs (19.8%) most commonly had DDIs. Contraindication was most commonly seen between inhaled corticosteroids and elvitegravir/cobicistat. A number of non-ART drugs, elvitegravir/cobicistat, antidiabetics, vitamins were independently associated with the presence of DDIs.

CONCLUSION

Results suggested the need for attention about co-medication in PLWH regardless of whether they are young or older. CNS drugs should be questioned more detailed in MSM, as well as CVS drugs in older HS patients. Elvitegravir/cobicistat is significantly associated with DDIs and switching to an unboosted INSTI should be considered in patients with multiple comorbidities.

Analysis of drug-drug interactions among patients receiving antiretroviral regimens using data from a large open-source prescription database

PURPOSE

Results of a study of contraindicated concomitant medication use among recipients of preferred antiretroviral therapy (ART) regimens are reported.

METHODS

A retrospective study was conducted to evaluate concomitant medication use in a cohort of previously treatment-naive, human immunodeficiency virus (HIV)-infected U.S. patients prescribed preferred ART regimens during the period April 2014-March 2015. Data were obtained from a proprietary longitudinal prescription database; elements retrieved included age, sex, and prescription data. The outcome of interest was the frequency of drug-drug interactions (DDIs) associated with concomitant use of contraindicated medications.

RESULTS

Data on 25,919 unique treatment-naive patients who used a preferred ART regimen were collected. Overall, there were 384 instances in which a contraindicated medication was dispensed for concurrent use with a recommended ART regimen. Rates of contraindicated concomitant medication use differed significantly by ART regimen; the highest rate (3.2%) was for darunavir plus ritonavir plus emtricitabine-tenofovir disoproxil fumarate (DRV plus RTV plus FTC/TDF), followed by elvitegravir-cobicistat-emtricitabine-tenofovir disoproxil fumarate (EVG/c/FTC/TDF)(2.8%). The highest frequencies of DDIs were associated with ART regimens that included a pharmacoenhancing agent: DRV plus RTV plus FTC/TDF (3.2%) and EVG/c/FTC/TDF (2.8%).

CONCLUSION

In a large population of treatment-naive HIV-infected patients, ART regimens that contained a pharmacoenhancing agent were involved most frequently in contraindicated medication-related DDIs. All of the DDIs could have been avoided by using therapeutic alternatives within the same class not associated with a DDI.