Sequential Population Pharmacokinetic Modeling of Lopinavir and Ritonavir in Healthy Volunteers and Assessment of Different Dosing Strategies

Abstract

Nonlinear mixed-effects modeling was applied to explore the relationship between lopinavir and ritonavir concentrations over 72 h following drug cessation and also to assess other lopinavir and ritonavir dosing strategies compared to the standard 400-mg-100-mg twice-daily dose. Data from 16 healthy volunteers were included. Possible covariates influencing lopinavir and ritonavir pharmacokinetics were also assessed. Data were modeled first separately and then together by using individually predicted ritonavir pharmacokinetic parameters in the final lopinavir model. The model was evaluated by means of a visual predictive check and external validation. A maximum-effect model in which ritonavir inhibited the elimination of lopinavir best described the relationship between ritonavir concentrations and lopinavir clearance (CL/F). A ritonavir concentration of 0.06 mg/liter was associated with a 50% maximum inhibition of the lopinavir CL/F. The population prediction of the lopinavir CL/F in the absence of ritonavir was 21.6 liters/h (relative standard error, 14.0%), and the apparent volume of distribution and absorption rate constant were 55.3 liters (relative standard error, 10.2%) and 0.57 h ؊1 (relative standard error, 0.39%), respectively. Overall, 92% and 94% of the observed concentrations were encompassed by the 95% prediction intervals for lopinavir and ritonavir, respectively, which is indicative of an adequate model. Predictions of concentrations from an external data set (HIV infected) (n ‫؍‬ 12) satisfied predictive performance criteria. Simulated lopinavir exposures at lopinavirritonavir doses of 200 mg-150 mg and 200 mg-50 mg twice daily were 38% and 65% lower, respectively, than that of the standard dose. The model allows a better understanding of the interaction between lopinavir and ritonavir and may allow a better prediction of lopinavir concentrations and assessments of different dosing strategies.Coformulated lopinavir-ritonavir (Kaletra; Abbott Laboratories, Chicago, IL) has demonstrated durable treatment efficacy in HIV-infected treatment-naïve and -experienced patients (12). It is approved for use at doses of 400 mg-100 mg twice daily and additionally at 800 mg-200 mg once daily for treatment-naïve patients in Europe and the United States (1, 2). Initially, lopinavir-ritonavir was available as soft-gel capsules, which required refrigerated storage and administration with food. However, a tablet formulation has been developed, with a diminished food effect, reduced variability compared to that of soft-gel capsules, and increased heat stability, therefore no longer needing refrigeration (9). Furthermore, data suggest a trend toward an increased bioavailability of the tablets (9).Hill et al. recently performed a systematic review of 17 dose-ranging pharmacokinetic studies involving ritonavirboosted protease inhibitors in order to assess the effects of ritonavir on different protease inhibitors and vice versa. Lopinavir concentrations were significantly increased in the presence of ritonavir and were c...

Population pharmacokinetic modelling of the changes in atazanavir plasma clearance caused by ritonavir plasma concentrations in HIV‐1 infected patients

“…RTV disposition was also best described by our one‐compartmental model with first‐order absorption and elimination, consistent with previous studies . Considering the values of k a reported for RTV when coadministered with LPV or darunavir (DRV) and our results, the RTV k a is not likely to be affected by the coadministered PI.…”

“…RTV disposition was also best described by our one‐compartmental model with first‐order absorption and elimination, consistent with previous studies . Considering the values of k a reported for RTV when coadministered with LPV or darunavir (DRV) and our results, the RTV k a is not likely to be affected by the coadministered PI. However, in the RTV‐boosted ATV regimens in the present study, CL/F RTV was almost half of the value reported for this parameter in RTV‐boosted LPV or DRV regimens, and therefore, plasma concentrations were higher .…”

“…Considering the values of k a reported for RTV when coadministered with LPV or darunavir (DRV) and our results, the RTV k a is not likely to be affected by the coadministered PI. However, in the RTV‐boosted ATV regimens in the present study, CL/F RTV was almost half of the value reported for this parameter in RTV‐boosted LPV or DRV regimens, and therefore, plasma concentrations were higher . The difference can probably be attributed to the effect of LPV and DRV as inducers of several CYP isoforms ; ATV, on the other hand, acts only as an inhibitor.…”

Model‐based approach to dose optimization of lopinavir/ritonavir when co‐administered with rifampicin

“…Previous studies have reported single compartmental elimination kinetics for ritonavir [8, 20–22]. However, possibly because of the rich sampling schedule used in our study, a two compartment model was more appropriate to describe the kinetics in our data.…”

“…higher doses and/or other target populations. However, extrapolation beyond the range of the data should be applied with caution [8, 9].…”