DMD 20917

Drug Metabolism and Disposition, 2010

Toxicology in Vitro, 2009

The metabolism and active transport of ritonavir and saquinavir were studied using sandwich-cultured rat hepatoyctes and rat liver microsomes. For ritonavir four comparable metabolites were observed in the sandwich-culture and in microsomes. For saquinavir eight metabolites were observed in sandwich-culture and 14 different metabolites in microsomes. Ketoconazole did not affect the metabolism of ritonavir in sandwich-culture or microsomes and slightly inhibited the metabolism of saquinavir in sandwich-culture. This inhibition resulted in a different metabolite profile for saquinavir in microsomes. Ritonavir had a pronounced inhibiting effect on the metabolism of saquinavir and affected the hydroxylation of 6b-testosterone negatively. In the active transport studies, cyclosporin A and PSC833 enhanced the metabolism of ritonavir, suggesting that ritonavir is normally excreted into the bile canaliculi. Verapamil, showed no effect on the metabolism of ritonavir. The intrinsic clearance was estimated at 1.65 and 67.5 ll/min/1 Â 10 6 cells and the hepatic metabolism clearance at 0.017 and 6.83 ml/min/SRW for ritonavir and saquinavir respectively. In conclusion, for saquinavir the metabolism rate and the amount of metabolites produced was higher than for ritonavir. Ritonavir had a strong inhibitory effect on the metabolism of saquinavir and seemed to be excreted into the bile.

Clinical Pharmacokinetics, 2010

Background and Objective: The pharmacokinetics of some HIV protease inhibitors are altered in patients with hepatic impairment. The TMC114-C134 study assessed the pharmacokinetics and safety of darunavir ritonavir 600 mg 100 mg twice daily in HIV-negative subjects with hepatic impairment (defined according to Child-Pugh classification A [mild] or B [moderate]) compared with matched, HIV-negative, healthy subjects. Methods: All subjects received darunavir ritonavir 600 mg 100 mg twice daily for 6 days with a morning dose on day 7. Pharmacokinetic profiles were obtained up to 72 hours post-dose for darunavir and 12 hours post-dose for ritonavir on day 7. Safety and tolerability were also assessed. Results: Darunavir pharmacokinetics in subjects with mild (n = 8) and moderate (n = 8) hepatic impairment were comparable to those in matched healthy control subjects (n = 16). In those with mild hepatic impairment, the least square mean ratios relative to healthy subjects for darunavir exposure (the area under the plasma concentration-time curve from 0 to 12 hours) and for maximum and minimum plasma concentrations were 0.94 (90% CI 0.75, 1.17), 0.88 (90% CI 0.73, 1.07) and 0.83 (90% CI 0.63, 1.10), respectively. In those with moderate hepatic impairment, these values were 1.20 (90% CI 0.90, 1.60), 1.22 (90% CI 0.95, 1.56) and 1.27 (90% CI 0.87, 1.85), respectively. Ritonavir pharmacokinetics were comparable between healthy subjects and those with mild hepatic impairment, but mean exposure was 50% higher in subjects with moderate hepatic impairment. Darunavir ritonavir was generally well tolerated, regardless of hepatic impairment. All adverse events were grade 1-2 in severity, except for a grade 3 increase in alanine aminotransferase reported in one subject with mild hepatic impairment. No adverse events led to discontinuation. Conclusions: The results of this study show that the pharmacokinetics of darunavir ritonavir 600 mg 100 mg are not affected by mild or moderate hepatic impairment. Therefore, it is recommended that dose adjustments of darunavir ritonavir are not required in patients with mild or moderate hepatic impairment.

Journal of Pharmaceutical Sciences, 2007

The aim of this study is to investigate in vivo the oral bioavailability of ritonavir and to evaluate the pharmacokinetic model that best describes the plasma concentration behavior after oral and intravenous administration. Male Wistar rats were intravenously administered at 3 mg dose of pure ritonavir and oral administered at 4.6 AE 2.5 mg of diluted Norvir 1 . Blood samples were taken by means of the jugular vein for a 24 h period of time. An analytical high-performance liquid chromatography (HPLC) technique was developed in order to quantify ritonavir plasma concentrations. A nonlinear modeling approach was used to estimate the pharmacokinetic parameters of interest. Results showed that a two-compartmental model with zero-order kinetic in the incorporation process of ritonavir into the body better fitted intravenous and oral data. The estimated oral bioavailability by means of noncompartmental and compartmental approaches resulted in 74% and 76.4%, respectively. These values confirm the ones obtained by other authors in the rat. In conclusion, a zero-order kinetic in the incorporation process at the administered doses suggests the saturation of the possible specialized transport mechanisms involved in the incorporation of ritonavir into the body. These results could justify the use of low doses of ritonavir when improving the bioavailability of other protease inhibitors (PIs) is required. ß

Antimicrobial Agents and Chemotherapy, 2004

Updated information and services can be found at: These include: REFERENCES http://aac.asm.org/content/48/7/2388#ref-list-1 at: This article cites 33 articles, 13 of which can be accessed free CONTENT ALERTS more» articles cite this article), Receive: RSS Feeds, eTOCs, free email alerts (when new http://journals.asm.org/site/misc/reprints.xhtml Information about commercial reprint orders: http://journals.asm.org/site/subscriptions/ To subscribe to to another ASM Journal go to: on April 3, 2014 by guest http://aac.asm.org/ Downloaded from on April 3, 2014 by guest http://aac.asm.org/

Journal of Pharmacology and Experimental Therapeutics, 2006

Indian Journal of Pharmaceutical Education and Research

Purpose: To compare pharmacokinetics and bioavailability of saquinavir (SQV) and ritonavir (RTV) and their optimized cyclodextrin complexes of anti-retro viral drugs after oral administration into rats. Methods: Rats were fasted overnight and dose equivalent to 10 mg/kg was administered orally via feeding tubes. Serial blood samples were collected, and plasma concentrations of both drugs and their complexes were determined using liquid chromatography tandem mass spectrometry, LCMS/MS. Results: After oral administration, half-life, apparent volume of distribution, total body clearance and bioavailabilities were calculated for both drugs and their optimized cyclodextrin complexes. The cyclodextrin complexes of both saquinavir (3860.93±138.50 ng.h/ml) and ritonavir (2300.19±118.21 ng.h/ml) had shown higher AUC 0-∞ values compared to pure drugs, saquinavir (2293.04±82.13 ng.h/ml) and ritonavir (1636.07±162.51 ng.h/ml). Conclusion: Orally administered cyclodextrin complexes of SQV and RTV had shown higher bioavailabilities and higher peak plasma concentrations compared to SQV and RTV.

Research Square (Research Square), 2021

Transporters in the human liver play a major role in the metabolism of endo-and xenobiotics. Apical (canalicular) transporters extrude compounds to the bile, while basolateral hepatocyte transporters promote the uptake or expel various compounds into the venous blood stream. In the present work we have examined the in vitro interactions of some key repurposed drugs advocated to treat COVID-19 (lopinavir, ritonavir, ivermectin, remdesivir and favipiravir), with the relevant key transporters in the hepatocytes. These transporters included the ABCB11/BSEP, ABCC2/MRP2, and MATE1 in the canalicular membrane, as well as ABCC3/MRP3, ABCC4/MRP4, OCT1, OATP1B1, OATP1B3, and NTCP, residing in the basolateral membrane. Lopinavir and ritonavir in low micromolar concentrations inhibited the ABCB11/BSEP and MATE1 exporters, as well as the OATP1B1/1B3 uptake transporters. Ritonavir had a similar inhibitory pattern, also inhibiting OCT1. Remdesivir strongly inhibited ABCC4/MRP4, OATP1B1/1B3, MATE1 and OCT1. Thus, these agents may cause severe drug-drug interactions and drug-induced liver injury. Favipiravir had no significant effect on any of these transporters. Since both general drug metabolism and drug-induced liver toxicity are strongly dependent on the functioning of these transporters, the variable interactions reported here may have important clinical relevance in the drug treatment of this viral disease and the existing co-morbidities.

Journal of Pharmacology and Experimental Therapeutics, 2003

Using a mouse model, we tested the effects of in vivo Pglycoprotein inhibition to enhance the oral uptake and penetration into pharmacological sanctuary sites of the human immunodeficiency virus protease inhibitor (HPI) saquinavir. The HPI ritonavir is frequently coadministered with saquinavir to improve saquinavir plasma levels since it strongly reduces the cytochrome P450 3A4-mediated metabolism of saquinavir. Previously, we demonstrated that ritonavir is not an efficient P-glycoprotein inhibitor in vivo, evidenced by the limited oral uptake of saquinavir and its penetration into brain and fetus. Increasing drug concentrations in these sites using more effective P-gp inhibitors might improve therapy but could also lead to toxicity. We orally coadministered ritonavir and saquinavir to mice, with or without the potent P-glycoprotein inhibitor N-(4-[2-(1,2,3,4-tetrahydro-6,7-dimethoxy-2-isoquinolinyl)ethyl]phenyl)-9,10-dihydro-5-methoxy-9-oxo-4-acridine carboxam-ide (GF120918). Upon GF120918 coadministration, two of seven P-glycoprotein-deficient animals died. Using a decreased ritonavir dose, GF120918 coadministration led to a 4.4-fold increase in the saquinavir plasma area under the curve in wild-type mice, whereas no such effect was observed in P-glycoprotein-deficient mice. Despite the decreased ritonavir dose, all mice did suffer from impaired gastric emptying. Including GF120918 in a multiple (bidaily) dosing regimen, we found continued accumulation of saquinavir in brain over several days, resulting in 10-fold higher levels compared with vehicle-treated mice. Transient ritonavir-related neurotoxicity, however, was observed after the fourth and final drug dosing. Clinical attempts to efficiently inhibit P-glycoprotein function for improved HPI disposition may therefore be feasible, but they should be performed without ritonavir and monitored carefully for unexpected toxicities.

Antimicrobial Agents and Chemotherapy, 2009

The effect of hepatic impairment on fosamprenavir/ritonavir pharmacokinetics was investigated. Sixty human immunodeficiency virus type 1-infected subjects, including 13, 20, and 10 subjects with mild, moderate, and severe hepatic impairment, respectively, and a comparator group of 17 subjects with normal hepatic function, were enrolled. Subjects with normal hepatic function received fosamprenavir at 700 mg plus ritonavir at 100 mg twice daily, whereas subjects with hepatic impairment received adjusted doses in anticipation of increased exposures. For subjects with mild hepatic impairment, the studied regimen of fosamprenavir 700 mg twice daily plus ritonavir 100 mg once daily delivered 17% higher values for the maximum plasma amprenavir concentration at the steady state (C max ), 22% higher values for the area under the plasma concentration versus time curve over the dosing interval at the steady state [AUC (0-) ], similar values for the concentration at the end of the dosing interval (C ), and 114% higher unbound C values. For subjects with moderate hepatic impairment, the studied dosage regimen of fosamprenavir at 300 mg twice daily plus ritonavir at 100 mg once daily delivered 27% lower plasma amprenavir C max values, 27% lower AUC (0-24) values, 57% lower C values, and 21% higher unbound amprenavir C values. For subjects with severe hepatic impairment, the studied dosage regimen of fosamprenavir at 300 mg twice daily plus ritonavir at 100 mg once daily delivered 19% lower plasma amprenavir C max values, 23% lower AUC (0-24) values, 38% lower C values, and similar unbound amprenavir C values. With a reduced ritonavir dosing frequency of 100 mg once daily, the plasma ritonavir AUC (0-24) values were 39% lower, similar, and 40% higher for subjects with mild, moderate, and severe hepatic impairment, respectively. The results of the study support the use of reduced fosamprenavir/ritonavir doses or dosing frequencies in the treatment of patients with hepatic impairment. No significant safety issues were identified; however, plasma amprenavir and ritonavir exposures were more variable in subjects with hepatic impairment, and those patients should be closely monitored for safety and virologic response.