Interaction of Rifampin and Darunavir-Ritonavir or Darunavir-Cobicistat In Vitro

ABSTRACT Treatment of HIV-infected patients coinfected with Mycobacterium tuberculosis is challenging due to drug-drug interactions (DDIs) between antiretrovirals (ARVs) and antituberculosis (anti-TB) drugs. The aim of this study was to quantify the effect of cobicistat (COBI) or ritonavir (RTV) in modulating DDIs between darunavir (DRV) and rifampin (RIF) in a human hepatocyte-based in vitro model. Human primary hepatocyte cultures were incubated with RIF alone or in combination with either COBI or RTV for 3 days, followed by coincubation with DRV for 1 h. The resultant DRV concentrations were quantified by high-performance liquid chromatography with UV detection, and the apparent intrinsic clearance (CL int.app. ) of DRV was calculated. Both RTV and COBI lowered the RIF-induced increases in CL int.app. in a concentration-dependent manner. Linear regression analysis showed that log 10 RTV and log 10 COBI concentrations were associated with the percent inhibition of RIF-induced elevations in DRV CL int.app. , where β was equal to −234 (95% confidence interval [CI] = −275 to −193; P &lt; 0.0001) and −73 (95% CI = −89 to −57; P &lt; 0.0001), respectively. RTV was more effective in lowering 10 μM RIF-induced elevations in DRV CL int.app. (half-maximal [50%] inhibitory concentration [IC 50 ] = 0.025 μM) than COBI (IC 50 = 0.223 μM). Incubation of either RTV or COBI in combination with RIF was sufficient to overcome RIF-induced elevations in DRV CL int.app. , with RTV being more potent than COBI. These data provide the first in vitro experimental insight into DDIs between RIF and COBI-boosted or RTV-boosted DRV and will be useful to inform physiologically based pharmacokinetic (PBPK) models to aid in optimizing dosing regimens for the treatment of patients coinfected with HIV and M. tuberculosis . </jats:p

Development and validation of an LC-MS/MS assay for the quantification of efavirenz in different biological matrices

Aim: The non-nucleoside reverse transcriptase inhibitor efavirenz is one of the most prescribed antiretroviral therapeutics. Efavirenz-containing therapy has become associated with the occurrence of CNS side effects, including sleep disturbances, depression and even psychosis. Results: The investigation of efavirenz distribution required the development of a versatile and sensitive method. In addition to plasma, quantification was required in brain tissue and phosphate-buffered saline. The assay presented here was linear from 1.9 to 500 ng/ml. Accuracy and precision ranged between 93.7 and 99.5%, and 1.5 and 5.6%, respectively. Discussion: The method developed here represents a versatile, sensitive and easy-to-use assay. The assay has been applied to in vitro and in vivo samples demonstrating reliable efavirenz quantification in multiple matrices

Efavirenz Is Predicted To Accumulate in Brain Tissue: an In Silico, In Vitro, and In Vivo Investigation

Adequate concentrations of efavirenz in the central nervous system (CNS) are necessary to suppress viral replication, but high concentrations may increase the likelihood of CNS adverse drug reactions. The aim of this investigation was to evaluate the efavirenz distribution in the cerebrospinal fluid (CSF) and the brain by using a physiologically based pharmacokinetic (PBPK) simulation for comparison with rodent and human data. The efavirenz CNS distribution was calculated using a permeability-limited model on a virtual cohort of 100 patients receiving efavirenz (600 mg once daily). Simulation data were then compared with human data from the literature and with rodent data. Wistar rats were administered efavirenz (10 mg kg of body weight(−1)) once daily over 5 weeks. Plasma and brain tissue were collected for analysis via liquid chromatography-tandem mass spectrometry (LC-MS/MS). The median maximum concentrations of drug (C(max)) were predicted to be 3,184 ng ml(−1) (interquartile range [IQR], 2,219 to 4,851 ng ml(−1)), 49.9 ng ml(−1) (IQR, 36.6 to 69.7 ng ml(−1)), and 50,343 ng ml(−1) (IQR, 38,351 to 65,799 ng ml(−1)) in plasma, CSF, and brain tissue, respectively, giving a tissue-to-plasma ratio of 15.8. Following 5 weeks of oral dosing of efavirenz (10 mg kg(−1)), the median plasma and brain tissue concentrations in rats were 69.7 ng ml(−1) (IQR, 44.9 to 130.6 ng ml(−1)) and 702.9 ng ml(−1) (IQR, 475.5 to 1,018.0 ng ml(−1)), respectively, and the median tissue-to-plasma ratio was 9.5 (IQR, 7.0 to 10.9). Although it is useful, measurement of CSF concentrations may give an underestimation of the penetration of antiretrovirals into the brain. The limitations associated with obtaining tissue biopsy specimens and paired plasma and CSF samples from patients make PBPK modeling an attractive tool for probing drug distribution