scholarly journals Multiple-Dose Pharmacokinetics and Pharmacodynamics of Abacavir Alone and in Combination with Zidovudine in Human Immunodeficiency Virus-Infected Adults

2000 ◽  
Vol 44 (8) ◽  
pp. 2061-2067 ◽  
Author(s):  
James A. McDowell ◽  
Yu Lou ◽  
William S. Symonds ◽  
Daniel S. Stein
Keyword(s):  
Human Immunodeficiency Virus ◽  
Steady State ◽  
Multiple Dose ◽  
Total Daily Dose ◽  
Pharmacokinetic Parameters ◽  
Pharmacokinetics And Pharmacodynamics ◽  
Time Curve ◽  
Immunodeficiency Virus ◽  
Multiple Dose Pharmacokinetics ◽  
Hiv 1

ABSTRACT Abacavir (1592U89) is a nucleoside reverse transcriptase inhibitor with potent activity against human immunodeficiency virus type 1 (HIV-1) when used alone or in combination with other antiretroviral agents. The present study was conducted to determine the multiple-dose pharmacokinetics and pharmacodynamics of abacavir in HIV-1-infected subjects following oral administration of daily doses that ranged from 600 to 1,800 mg, with and without zidovudine. Seventy-nine subjects received abacavir monotherapy for 4 weeks (200, 400, or 600 mg every 8 hours [TID] and 300 mg every 12 h [BID]) and thereafter received either zidovudine (200 mg TID or 300 mg BID) or matching placebo with abacavir for 8 additional weeks. Pharmacokinetic parameters were calculated for abacavir after administration of the first dose and at week 4 and for abacavir, zidovudine, and its glucuronide metabolite at week 12. The concentrations of abacavir in cerebrospinal fluid were determined in a subset of subjects. Steady-state plasma abacavir concentrations were achieved by week 4 of monotherapy and persisted to week 12. At steady state, abacavir pharmacokinetic parameters (area under the plasma concentration-time curve for a dosing interval [AUCtau] and peak concentration [C max]) were generally proportional to dose over the range of a 600- to 1,200-mg total daily dose. Coadministration of zidovudine with abacavir produced a small and inconsistent effect on abacavir pharmacokinetic parameters across the different doses. At the clinical abacavir dose (300 mg BID) zidovudine coadministration had no effect on the abacavir AUCtau, which is most closely associated with efficacy. Zidovudine pharmacokinetics appeared to be unaffected by abacavir. Statistically significant but weak relationships were found for the change in the log10 HIV-1 RNA load from the baseline to week 4 versus total daily AUCtau and C tau(P < 0.05). The incidence of nausea was significantly associated with total daily AUCtau andC max. In conclusion, abacavir has predictable pharmacokinetic characteristics following the administration of multiple doses.

scholarly journals Effects of Valproic Acid Coadministration on Plasma Efavirenz and Lopinavir Concentrations in Human Immunodeficiency Virus-Infected Adults

2004 ◽  
Vol 48 (11) ◽  
pp. 4328-4331 ◽  
Author(s):  
Robert DiCenzo ◽  
Derick Peterson ◽  
Kim Cruttenden ◽  
Gene Morse ◽  
Garret Riggs ◽  
...  
Keyword(s):  
Human Immunodeficiency Virus ◽  
Valproic Acid ◽  
Geometric Mean ◽  
Pharmacokinetic Parameters ◽  
Time Curve ◽  
Blood Samples ◽  
Immunodeficiency Virus ◽  
Before And After ◽  
Trough Concentrations ◽  
Hiv 1

ABSTRACT Valproic acid (VPA) has the potential to benefit patients suffering from human immunodeficiency virus (HIV)-associated cognitive impairment. The purpose of this study was to determine if VPA affects the plasma concentration of efavirenz (EFV) or lopinavir. HIV type 1 (HIV-1)-infected patients receiving EFV or lopinavir-ritonavir (LPV/r) had 9 or 10 blood samples drawn over 8 to 24 h of a dosing interval at steady state before and after receiving 250 mg of VPA twice daily for 7 days. VPA blood samples drawn before (C 0) and 8 h after the morning dose (8 h) were compared to blood samples from a group of HIV-1-infected subjects who were taking either combined nucleoside reverse transcriptase inhibitors alone or had discontinued antiretroviral therapy. Pharmacokinetic parameters were calculated by noncompartmental analysis, and tests of bioequivalence were based on 90% confidence intervals (CIs) for ratios or differences. The geometric mean ratio (GMR) (90% CI) of the areas under the concentration-time curve from 0 to 24 h (AUC0-24s) of EFV (n = 11) with and without VPA was 1.00 (0.85, 1.17). The GMR (90% CI) of the AUC0-8s of LPV (n = 8) with and without VPA was 1.38 (0.98, 1.94). The differences (90% CI) in mean C 0 and 8-h VPA concentrations versus the control (n = 11) were −1.0 (−9.4, 7.4) μg/ml and −2.1 (−11.1, 6.9) μg/ml for EFV (n = 10) and −5.0 (−13.2, 3.3) μg/ml and −6.7 (−17.6, 4.2) μg/ml for LPV/r (n = 11), respectively. EFV administration alone is bioequivalent to EFV and VPA coadministration. LPV concentrations tended to be higher when the drug was combined with VPA. Results of VPA comparisons fail to raise concern that coadministration with EFV or LPV/r will significantly influence trough concentrations of VPA.

scholarly journals Steady-State Pharmacokinetics of Amprenavir Coadministered with Ritonavir in Human Immunodeficiency Virus Type 1-Infected Patients

2003 ◽  
Vol 47 (1) ◽  
pp. 118-123 ◽  
Author(s):  
Cecile Goujard ◽  
Isabelle Vincent ◽  
Jean-Luc Meynard ◽  
Nathalie Choudet ◽  
Diane Bollens ◽  
...  
Keyword(s):  
Human Immunodeficiency Virus ◽  
Steady State ◽  
Human Immunodeficiency Virus Type ◽  
Virus Type ◽  
Time Curve ◽  
Concentration Time ◽  
Immunodeficiency Virus ◽  
The Mean ◽  
Hiv 1

ABSTRACT The protease inhibitor (PI) ritonavir is used as a strong inhibitor of cytochrome P450 3A4, which boosts the activities of coadministered PIs, resulting in augmented plasma PI levels, simplification of the dosage regimen, and better efficacy against resistant viruses. The objectives of the present open-label, multiple-dose study were to determine the steady-state pharmacokinetics of amprenavir administered at 600 mg twice daily (BID) and ritonavir administered at 100 mg BID in human immunodeficiency virus type 1 (HIV-1)-infected adults treated with different antiretroviral combinations including or not including a nonnucleoside reverse transcriptase inhibitor (NNRTI). Nineteen patients completed the study. The steady-state mean minimum plasma amprenavir concentration (C min,ss) was 1.92 μg/ml for patients who received amprenavir and ritonavir without an NNRTI and 1.36 μg/ml for patients who received amprenavir and ritonavir plus efavirenz. For patients who received amprenavir-ritonavir without an NNRTI, the steady-state mean peak plasma amprenavir concentration (C max,ss) was 7.12 μg/ml, the area under the concentration-time curve from 0 to 10 h (AUC0-10) was 32.06 μg · h/ml, and the area under the concentration-time curve over a dosing interval (12 h) at steady-state (AUCss) was 35.74 μg · h/ml. Decreases in the mean values of C min,ss (29%), C max,ss (42%), AUC0-10 (42%), and AUCss (40%) for amprenavir occurred when efavirenz was coadministered with amprenavir-ritonavir. No unexpected side effects were observed. As expected, coadministration of amprenavir with ritonavir resulted in an amprenavir C min,ss markedly higher than those previously reported for the marketed dose of amprenavir. When amprenavir-ritonavir was coadministered with efavirenz, amprenavir-ritonavir maintained a mean amprenavir C min,ss above the mean 50% inhibitory concentration of amprenavir previously determined for both wild-type HIV-1 isolates and HIV-1 strains isolated from PI-experienced patients. These data support the use of low-dose ritonavir to enhance the level of exposure to amprenavir and increase the efficacy of amprenavir.

scholarly journals Steady-State Pharmacokinetics of a Double-Boosting Regimen of Saquinavir Soft Gel plus Lopinavir plus Minidose Ritonavir in Human Immunodeficiency Virus-Infected Adults

2004 ◽  
Vol 48 (11) ◽  
pp. 4256-4262 ◽  
Author(s):  
Esteban Ribera ◽  
Rosa M. Lopez ◽  
Marjorie Diaz ◽  
Leonor Pou ◽  
Lidia Ruiz ◽  
...  
Keyword(s):  
Human Immunodeficiency Virus ◽  
Steady State ◽  
Rescue Therapy ◽  
Pharmacokinetic Parameters ◽  
Time Curve ◽  
Minimum Concentration ◽  
Immunodeficiency Virus ◽  
Strong Linear Correlation ◽  
Drug Doses ◽  
Therapeutic Doses

ABSTRACT Management of treatment-experienced human immunodeficiency virus patients has become complex, and therapy may need to include two protease inhibitors at therapeutic doses. The objective of this study was to characterize the pharmacokinetics in serum of saquinavir (1,000 mg twice daily [b.i.d.]), lopinavir (400 mg b.i.d.), and ritonavir (100 mg b.i.d.) in a multidrug rescue therapy study and to investigate whether steady-state pharmacokinetics of lopinavir-ritonavir are affected by coadministration of saquinavir. Forty patients were included (25 given ritonavir, lopinavir, and saquinavir and 15 given ritonavir and lopinavir). The median pharmacokinetic parameters of lopinavir were as follows: area under the concentration-time curve from 0 to 12 h (AUC0-12), 85.1 μg/ml · h; maximum concentration of drug in serum (C max), 10.0 μg/ml; trough concentration of drug in serum (C trough), 7.3 μg/ml; and minimum concentration of drug in serum (C min), 5.5 μg/ml. Lopinavir concentrations were similar in patients with and without saquinavir. The median pharmacokinetic parameters for saquinavir were as follows: AUC0-12, 22.9 μg/ml · h; C max, 2.9 μg/ml; C trough, 1.6 μg/ml; and C min, 1.4 μg/ml. There was a strong linear correlation between lopinavir and ritonavir and between saquinavir and ritonavir concentrations in plasma. The correlation between lopinavir and saquinavir levels was weaker. We found higher saquinavir concentrations in women than in men, with no difference in lopinavir levels. Only patients with very high body weight presented lopinavir and saquinavir concentrations lower than the overall group. Ritonavir has a double-boosting function for both lopinavir and saquinavir, and in terms of pharmacokinetics, the drug doses selected seemed appropriate for combining these agents in a dual protease inhibitor-based antiretroviral regimen for patients with several prior virologic failures.

scholarly journals Pharmacokinetics of Azithromycin Administered Alone and with Atovaquone in Human Immunodeficiency Virus-Infected Children

1999 ◽  
Vol 43 (6) ◽  
pp. 1516-1519 ◽  
Author(s):  
Leock Y. Ngo ◽  
Ram Yogev ◽  
Wayne M. Dankner ◽  
Walter T. Hughes ◽  
Sandra Burchett ◽  
...  
Keyword(s):  
Human Immunodeficiency Virus ◽  
Steady State ◽  
Pharmacokinetic Parameters ◽  
Time Curve ◽  
Concentration Time ◽  
Significant Difference ◽  
Immunodeficiency Virus ◽  
The Mean ◽  
Clinically Significant ◽  
To Receive

ABSTRACT To evaluate if atovaquone (ATQ) interacts pharmacokinetically with azithromycin (AZ) in human immunodeficiency virus-infected children, 10 subjects (ages, 4 to 13 years) were randomized in a crossover study to receive AZ (5 mg/kg/day) alone (ALONE) or AZ (5 mg/kg/day) and ATQ (30 mg/kg/day) simultaneously (SIM) prior to receiving AZ and ATQ staggered by 12 h. Despite a lack of significant difference in the mean AZ pharmacokinetic parameters, the steady-state values of AZ’s area under the concentration-time curve from 0 to 24 h and maximum concentration in serum were consistently lower (n = 7 of 7) for the SIM regimen than they were for the ALONE regimen. A larger study will be required to determine if ATQ affects AZ pharmacokinetics and efficacy in a clinically significant manner.

scholarly journals Effect of fluconazole on the steady-state pharmacokinetics of delavirdine in human immunodeficiency virus-positive patients.

1997 ◽  
Vol 41 (9) ◽  
pp. 1892-1897 ◽  
Author(s):  
M T Borin ◽  
S R Cox ◽  
B D Herman ◽  
B J Carel ◽  
R D Anderson ◽  
...  
Keyword(s):  
Human Immunodeficiency Virus ◽  
Steady State ◽  
Fungal Infections ◽  
Reversed Phase ◽  
Pharmacokinetic Parameters ◽  
Control Group ◽  
Blood Samples ◽  
Immunodeficiency Virus ◽  
Hiv 1 ◽  
Delavirdine Mesylate

Fluconazole, an inhibitor of certain human cytochrome P-450 isozymes, is used for the prevention and treatment of a broad range of fungal infections that predominantly affect immunocompromised individuals. This study evaluated the influence of fluconazole on the steady-state pharmacokinetics of delavirdine, a nonnucleoside inhibitor of human immunodeficiency virus type 1 (HIV-1) reverse transcriptase, in 13 HIV-1-infected patients with CD4 counts ranging from 186 to 480/mm3. Both the control group (n = 5) and the fluconazole group (n = 8) received 300 mg of delavirdine mesylate every 8 h for 30 days; subjects in the fluconazole group took a 400-mg, once-daily dose of fluconazole on study days 16 to 30. Harvested plasma from serial blood samples collected on days 15, 16, and 30 were assayed for concentrations of delavirdine and its N-desalkyl metabolite by a reversed-phase high-pressure liquid chromatography (HPLC) method. Blood samples obtained on days 16 and 30 were also assayed for fluconazole by HPLC. Delavirdine mesylate alone and in combination with fluconazole was well tolerated. There were no significant differences (P > 0.16) in delavirdine pharmacokinetic parameters between treatment groups on day 15 or day 30. After coadministration of fluconazole and delavirdine mesylate for 2 weeks (day 30), no significant differences (P > 0.058) were observed in any delavirdine pharmacokinetic parameters relative to those after receiving delavirdine mesylate alone (day 15) after in the fluconazole group. Fluconazole pharmacokinetic parameters were similar to those previously reported for healthy volunteers and HIV-positive patients. On the basis of these findings, fluconazole and delavirdine mesylate may be taken concurrently without adjustment of the dose of either drug.

scholarly journals Single-Dose Pharmacokinetics and Safety of Abacavir (1592U89), Zidovudine, and Lamivudine Administered Alone and in Combination in Adults with Human Immunodeficiency Virus Infection

1999 ◽  
Vol 43 (7) ◽  
pp. 1708-1715 ◽  
Author(s):  
Laurene H. Wang ◽  
Gregory E. Chittick ◽  
James A. McDowell
Keyword(s):  
Human Immunodeficiency Virus ◽  
Adverse Events ◽  
Nucleoside Analogs ◽  
Neck Stiffness ◽  
Time Curve ◽  
Pharmacokinetic Interactions ◽  
Immunodeficiency Virus ◽  
The Mean ◽  
Clinically Significant ◽  
Hiv 1

ABSTRACT Abacavir (1592U89), a nucleoside reverse transcriptase inhibitor with in vitro activity against human immunodeficiency virus type-1 (HIV-1), has been evaluated for efficacy and safety in combination regimens with other nucleoside analogs, including zidovudine (ZDV) and lamivudine (3TC). To evaluate the potential pharmacokinetic interactions between these agents, 15 HIV-1-infected adults with a median CD4+ cell count of 347 cells/mm3 (range, 238 to 570 cells/mm3) were enrolled in a randomized, seven-period crossover study. The pharmacokinetics and safety of single doses of abacavir (600 mg), ZDV (300 mg), and 3TC (150 mg) were evaluated when each drug was given alone or when any two or three drugs were given concurrently. The concentrations of all drugs in plasma and the concentrations of ZDV and its 5′-glucuronide metabolite, GZDV, in urine were measured for up to 24 h postdosing, and pharmacokinetic parameter values were calculated by noncompartmental methods. The maximum drug concentration (C max), the area under the concentration-time curve from time zero to infinity (AUC0–∞), time to C max(T max), and apparent elimination half-life (t 1/2) of abacavir in plasma were unaffected by coadministration with ZDV and/or 3TC. Coadministration of abacavir with ZDV (with or without 3TC) decreased the meanC max of ZDV by approximately 20% (from 1.5 to 1.2 μg/ml), delayed the median T max for ZDV by 0.5 h, increased the mean AUC0–∞ for GZDV by up to 40% (from 11.8 to 16.5 μg · h/ml), and delayed the medianT max for GZDV by approximately 0.5 h. Coadministration of abacavir with 3TC (with or without ZDV) decreased the mean AUC0–∞ for 3TC by approximately 15% (from 5.1 to 4.3 μg · h/ml), decreased the meanC max by approximately 35% (from 1.4 to 0.9 μg/ml), and delayed the median T max by approximately 1 h. While these changes were statistically significant, they are similar to the effect of food intake (for ZDV) or affect an inactive metabolite (for GZDV) or are relatively minor (for 3TC) and are therefore not considered to be clinically significant. No significant differences were found in the urinary recoveries of ZDV or GZDV when ZDV was coadministered with abacavir. There was no pharmacokinetic interaction between ZDV and 3TC. Mild to moderate headache, nausea, lymphadenopathy, hematuria, musculoskeletal chest pain, neck stiffness, and fever were the most common adverse events reported by those who received abacavir. Coadministration of ZDV or 3TC with abacavir did not alter this adverse event profile. The three-drug regimen was primarily associated with gastrointestinal events. In conclusion, no clinically significant pharmacokinetic interactions occurred between abacavir, ZDV, and 3TC in HIV-1-infected adults. Coadministration of abacavir with ZDV or 3TC produced mild changes in the absorption and possibly the urinary excretion characteristics of ZDV-GZDV and 3TC that were not considered to be clinically significant. Coadministration of abacavir with ZDV and/or 3TC was generally well tolerated and did not produce unexpected adverse events.

scholarly journals Steady-State Pharmacokinetics of Abacavir in Plasma and Intracellular Carbovir Triphosphate following Administration of Abacavir at 600 Milligrams Once Daily and 300 Milligrams Twice Daily in Human Immunodeficiency Virus-Infected Subjects

2009 ◽  
Vol 53 (4) ◽  
pp. 1532-1538 ◽  
Author(s):  
Graeme Moyle ◽  
Marta Boffito ◽  
Carl Fletcher ◽  
Chris Higgs ◽  
Phillip E. Hay ◽  
...  
Keyword(s):  
Human Immunodeficiency Virus ◽  
High Performance ◽  
Pharmacokinetic Parameters ◽  
Virologic Suppression ◽  
Open Label ◽  
Time Curve ◽  
Mixed Effect ◽  
Once Daily ◽  
Immunodeficiency Virus ◽  
And Gender

ABSTRACT Abacavir (ABC) is administered either at 600 mg once daily (ABC 600 mg QD) or 300 mg twice daily (ABC 300 mg BID) in anti-human immunodeficiency virus (anti-HIV) combination therapy. Although ABC plasma pharmacokinetics following each regimen has been well defined, no study has directly compared the regimens with respect to pharmacokinetics of ABC's active intracellular anabolite, carbovir-triphosphate (CBV-TP). In an open-label, two-period, crossover study, 34 HIV-infected male and female subjects stabilized on antiretroviral regimens containing either ABC 600 mg QD or ABC 300 mg BID received their usual doses on days −1 and 1 and then switched regimens for days 2 to 11. Serial blood samples collected on days 1 and 11 were assayed for plasma ABC and intracellular CBV-TP concentrations using validated high-performance liquid chromatography-tandem mass spectrometry methods. Pharmacokinetic parameters were calculated using noncompartmental methods. Analysis of variance with a mixed-effect model was performed for treatment and gender comparisons. In 27 evaluable subjects, the regimens provided bioequivalent ABC daily areas under the concentration-time curve from 0 to 24 h (AUC0-24) and comparable CBV-TP concentrations at the end of the dosing interval (C τ). As expected, ABC QD resulted in 109% higher ABC maximum concentrations of drug in plasma (C max) than did ABC BID. ABC QD also resulted in 32% higher CBV-TP AUC0-24 and 99% higher CBV-TP C max than did ABC BID. Females had a 38% higher weight-adjusted ABC AUC0-24 and 81% higher weight-adjusted CBV-TP AUC0-24 than did males. Virologic suppression was maintained during regimen switch, and no tolerability differences between regimens were observed. In conclusion, this study showed that ABC 600 mg QD and ABC 300 mg BID regimens led to similar intracellular CBV-TP C τ values, thus providing pharmacokinetic support for the interchangeability of these two regimens. Women had higher intracellular CBV-TP exposure than did men.

scholarly journals Single-Dose Safety and Pharmacokinetics of Amprenavir (141W94), a Human Immunodeficiency Virus Type 1 (HIV-1) Protease Inhibitor, in HIV-Infected Children

2005 ◽  
Vol 49 (1) ◽  
pp. 336-341 ◽  
Author(s):  
Ram Yogev ◽  
Andrea Kovacs ◽  
Ellen G. Chadwick ◽  
James D. Homans ◽  
Yu Lou ◽  
...  
Keyword(s):  
Human Immunodeficiency Virus ◽  
Phase I ◽  
Human Immunodeficiency Virus Type ◽  
Virus Type ◽  
Pharmacokinetic Parameters ◽  
Maximum Plasma ◽  
Immunodeficiency Virus ◽  
Hiv 1 ◽  
Dose Proportional

ABSTRACT A phase I, open-label, dose-escalating trial was conducted to evaluate the safety, tolerability, and pharmacokinetics of single, oral doses of amprenavir (141W94), a potent inhibitor of human immunodeficiency virus type 1 (HIV-1) protease, in 20 HIV-infected children 4 to 12 years of age. The doses of amprenavir evaluated, 5, 10, 15, and 20 mg/kg of body weight, were comparable to those evaluated in adult phase I and II studies. The most common clinical adverse event associated with amprenavir, administered as soft gelatin capsules, was nausea. Amprenavir was rapidly absorbed, with a mean time to maximum concentration (T max) occurring 0.95 to 1.58 h after dosing. The area under the concentration-time curve (AUC0 → ∞) was dose proportional, and the mean maximum plasma concentration (C max) increased linearly in a less than dose-proportional manner. Amprenavir was eliminated relatively slowly, with a mean terminal-phase half-life (t 1/2) of 6.17 to 8.28 h. The t 1/2, apparent total clearance, and apparent volume of distribution during the elimination phase were dose independent. Considerable interpatient variability was seen for all pharmacokinetic parameters of amprenavir. The results of this study suggest that 20 mg of amprenavir/kg administered twice a day should be used in future pediatric studies.

scholarly journals Safety and Pharmacokinetics of Once-Daily Regimens of Soft-Gel Capsule Saquinavir plus Minidose Ritonavir in Human Immunodeficiency Virus-Negative Adults

2000 ◽  
Vol 44 (10) ◽  
pp. 2672-2678 ◽  
Author(s):  
J. Michael Kilby ◽  
Greg Sfakianos ◽  
Nick Gizzi ◽  
Peggy Siemon-Hryczyk ◽  
Eric Ehrensing ◽  
...  
Keyword(s):  
Human Immunodeficiency Virus ◽  
Combined Therapy ◽  
Treatment Options ◽  
Control Group ◽  
Post Dose ◽  
Time Curve ◽  
Once Daily ◽  
Treatment Regimens ◽  
Immunodeficiency Virus ◽  
Hiv 1

ABSTRACT Human immunodeficiency virus type 1 (HIV-1) protease inhibitors have dramatically improved treatment options for HIV infection, but frequent dosing may impact adherence to highly active antiretroviral treatment regimens (HAART). Previous studies demonstrated that combined therapy with ritonavir and saquinavir allows a decrease in frequency of saquinavir dosing to twice daily. In this study, we evaluated the safety and pharmacokinetics of combining once-daily doses of the soft-gel capsule (SGC) formulation of saquinavir (saquinavir-SGC) and minidose ritonavir. Forty-four healthy HIV-negative volunteers were randomized into groups receiving once-daily doses of saquinavir-SGC (1,200 to 1,800 mg) plus ritonavir (100 to 200 mg) or a control group receiving only saquinavir-SGC (1,200 mg) three times daily. Saquinavir-SGC alone and saquinavir-SGC–ritonavir combinations were generally well tolerated, and there were no safety concerns. Addition of ritonavir (100 mg) to saquinavir-SGC (1,200 to 1,800 mg/day) increased the area under the concentration-time curve (AUC) for saquinavir severalfold, and the intersubject peak concentration in plasma and AUC variability were reduced compared to those achieved with saquinavir-SGC alone (3,600 mg/day), while trough saquinavir levels (24 h post-dose) were substantially higher than the 90% inhibitory concentration calculated from HIV-1 clinical isolates. Neither increasing the saquinavir-SGC dose to higher than 1,600 mg nor increasing ritonavir from 100 to 200 mg appeared to further enhance the AUC. These results suggest that an all once-daily HAART regimen, utilizing saquinavir-SGC plus a more tolerable low dose of ritonavir, may be feasible. Studies of once-daily saquinavir-SGC (1,600 mg) in combination with ritonavir (100 mg) in HIV-infected patients are underway.

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