Population pharmacokinetics of lopinavir in combination with ritonavir in HIV-1-infected patients.

AIMS: To develop a population pharmacokinetic model for lopinavir in combination with ritonavir, in which the interaction between both drugs was characterized, and in which relationships between patient characteristics and pharmacokinetics were identified. METHODS: The pharmacokinetics of lopinavir in combination with ritonavir were described using NONMEM (version V, level 1.1). First, ritonavir data were fitted to a previously developed model to obtain individual Bayesian estimates of pharmacokinetic parameters. Hereafter, an integrated model for the description of the pharmacokinetics of lopinavir with ritonavir was designed. RESULTS: From 122 outpatients 748 lopinavir and 748 ritonavir plasma concentrations were available for analysis. The interaction between the drugs was described by a time-independent inverse relationship between the exposure to ritonavir over a dosing-interval and the apparent clearance (CL/F) of lopinavir. The model parameters volume of distribution and absorption rate constant were 61.6 l (95% prediction interval (PI) 22.4, 83.7) and 0.564 h(-1) (95% PI 0.208, 0.947), respectively. The model yielded a theoretical value for the CL/F of lopinavir without ritonavir of 14.8 l h(-1) (95%PI 12.1, 20.1), which translates to a value of 5.73 l h(-1) in the presence of ritonavir. The only factor with significant effect on the pharmacokinetics was concurrent use of non-nucleoside reverse transcriptase inhibitors (NNRTI), which increased the CL/F of lopinavir by 39% (P < 0.001). CONCLUSIONS: We have developed a model that has defined a time-independent inverse relationship between the exposure to ritonavir and the CL/F of lopinavir, and provided an adequate description of the pharmacokinetic parameters for the latter. Concomitant use of the NNRTIs efavirenz and nevirapine increased the CL/F of lopinavir.

Bioanalysis of HIV protease inhibitors in samples from sanctuary sites.

The human immunodeficiency virus (HIV) is present in several sites inside the human body, which are hardly accessible to antiretroviral drugs, the so-called sanctuary sites. The most important sanctuary sites are cerebrospinal fluid (CSF), peripheral blood mononuclear cells (PBMCs) and seminal plasma. The determination of drug concentrations in these sanctuary sites may form an important step in treatment optimisation of HIV-infected individuals. However, bioanalysis in these sites is hampered by several factors with regard to sample preparation, chromatography and detection. In this review, we will discuss these issues and give an overview of published methods using high-performance liquid chromatography (HPLC) for the bioanalysis of HIV protease inhibitors in CSF, PBMCs and seminal plasma.

Simultaneous quantification of the new HIV protease inhibitors atazanavir and tipranavir in human plasma by high-performance liquid chromatography coupled with electrospray ionization tandem mass spectrometry.

We have developed and validated an assay, using liquid chromatography coupled with electrospray tandem mass spectrometry (LC-MS/MS), for the quantification of the novel protease inhibitors (PIs) atazanavir and tipranavir. The sample pre-treatment consisted of protein precipitation with a mixture of methanol and acetronitrile using 100 microl plasma for atazanavir and 50 microl for tipranavir. Chromatographic separation was achieved on an Inertsil ODS3 column (50 mm x 2.0 mm i.d., particle size 5 microm), with a quick stepwise gradient using an acetate buffer (pH 5) and methanol, at a flow rate of 0.5 ml/min. The analytical run time was 5.5 min. The triple quadrupole mass spectrometer operated in the positive ion-mode and multiple reaction monitoring (MRM) was used for drug quantification. The assay was linear over a concentration range of 0.05-10 microg/ml for atazanavir and 0.1-75 microg/ml for tipranavir. Saquinavir-d5 was used as internal standard. The intra- and inter-day coefficients of variation were less than 3.8% for atazanavir and less than 10.4% for tipranavir. Accuracies were within +/-7.3 and +/-7.2% for atazanavir and tipranavir, respectively. Both drugs were stable under various relevant storage conditions. The validated concentration ranges proved to be adequate to measure concentrations of human immunodeficiency virus type-1 (HIV-1)-infected individuals. The developed method could easily be combined with a previously developed LC-MS/MS assay for the quantification of protease inhibitors.

Rapid quantification of HIV protease inhibitors in human plasma by high-performance liquid chromatography coupled with electrospray ionization tandem mass spectrometry.

HIV protease inhibitors are important antiretroviral drugs which have substantially reduced the morbidity and mortality associated with HIV-1 infection. Recent data have shown relationships between plasma concentrations of the protease inhibitors and clinical response, which makes therapeutic drug monitoring valuable. We have developed and validated an assay, using liquid chromatography coupled with electrospray tandem mass spectrometry (LC/MS/MS), for the routine quantification of the six licensed protease inhibitors (amprenavir, indinavir, lopinavir, nelfinavir, ritonavir and saquinavir) and the pharmacologically active nelfinavir metabolite M8 in plasma. The sample pretreatment consisted of protein precipitation with a mixture of methanol and acetronitrile using only 100 microl of plasma. Chromatographic separation was performed on an Inertsil ODS3 column (50 x 2.0 mm i.d., particle size 5 microm), with a quick stepwise gradient using an acetate buffer (pH 5) and methanol, at a flow rate of 0.5 ml min(-1). The analytical run time was 5.5 min. The use of a 96-well plate autosampler allowed batch sizes up to 150 patient samples. The triple-quadrupole mass spectrometer was operated in the positive ion mode and multiple reaction monitoring was used for drug quantification. The method was validated over the concentration ranges 0.01-10 microg ml(-1) for indinavir and saquinavir, 0.1-10 microg ml(-1) for amprenavir, 0.05-10 microg ml(-1) for nelfinavir and ritonavir, 0.1-20 microg ml(-1) for lopinavir and 0.01-5 microg ml(-1) for M8. Saquinavir-d(5) and indinavir-d(6) were used as internal standards. The coefficients of variation were always <10% for both intra-day and inter-day precisions for each compound. Mean accuracies were also between the designated limits (+/-15%). The validated concentration ranges proved to be adequate in daily practice. This robust and fast LC/MS/MS assay is now successfully applied for routine therapeutic drug monitoring and pharmacokinetic studies in our hospital.

Prognostic factors for the clinical effectiveness of fluconazole in the treatment of oral candidiasis in HIV-1-infected individuals.

OBJECTIVE: To identify prognostic factors for the clinical effectiveness of fluconazole in HIV-1-infected patients with oropharyngeal candidiasis. DESIGN AND SETTING: The study was designed as a prospective, open label, non-comparative, dose escalating, single centre trial. PATIENTS AND METHODS: Thirty-four HIV-1-infected patients with oropharyngeal Candida infection were treated with 50 or 100mg fluconazoleday(-1), depending on the clinical manifestation (erythematous or pseudomembranous). The dose was doubled weekly until clinical cure. The predictive value of potential prognostic factors for the duration of treatment and cumulative fluconazole dose until cure was studied: exposure to fluconazole, previous use of fluconazole, the use of antiretroviral drugs, the CD4(+) cell count, erythematous or pseudomembranous appearance, the minimum inhibitory concentration (MIC) for fluconazole of the isolated Candida strain, and xerostomia. RESULTS: Twenty-eight patients (with 30 episodes of oropharyngeal candidiasis) were evaluated. Twenty-five episodes were cured within 1-week of treatment, the remaining five episodes were cured within 2 weeks. No predictive value for any of the studied factors on the duration of fluconazole treatment or the cumulative fluconazole dose until cure was demonstrated. CONCLUSION: Because of the high susceptibility to fluconazole and the positive clinical outcome, the variation in outcome measurements was too modest to establish a significant relationship between any of the investigated potentially prognostic factors and the cumulative fluconazole dose and the duration of treatment to reach cure. On the other hand it can be concluded, that fluconazole is very effective in patients with advanced HIV infection and low CD4(+) cell counts, even if they are not using antiretroviral agents.

Can fluconazole concentrations in saliva be used for therapeutic drug monitoring?

The saliva/plasma concentration ratio of fluconazole was investigated in 22 HIV-1-infected individuals with an oropharyngeal Candida infection to determine whether saliva fluconazole concentrations could provide useful information for therapeutic drug monitoring in this population. Steady-state paired plasma and saliva samples were obtained after approximately 1 week of treatment with 50-or 100-mg fluconazole as capsules. A significant correlation between plasma and salivary levels of fluconazole was observed. The median saliva/plasma concentration ratio was 1.3 and was independent of the ingested dose and the plasma fluconazole concentration. The prediction of fluconazole concentrations in plasma from the concentrations in saliva was, although unbiased, not precise. From these findings, the authors conclude that although stimulated salivary fluconazole concentrations are significantly correlated with plasma concentrations, it is not possible to predict plasma fluconazole levels from the salivary concentrations with adequate precision. However, saliva fluconazole concentrations have sufficient value to test for compliance and even semiquantitative prediction of plasma concentrations.

The effect of fluconazole on ritonavir and saquinavir pharmacokinetics in HIV-1-infected individuals.

AIMS: To study the effect of fluconazole on the steady-state pharmacokinetics of the protease inhibitors ritonavir and saquinavir in HIV-1-infected patients. METHODS: Five subjects treated with saquinavir and three with ritonavir received the protease inhibitor alone (saquinavir 1200 mg three times daily, ritonavir 600 mg twice daily) on day 1, and the same protease inhibitor in combination with fluconazole (400 mg on day 2 and 200 mg on days 3 to 8). Pharmacokinetic parameters were determined on days 1 and 8. RESULTS: In the saquinavir group, the median increase in the area under the plasma concentration vs time curve was 50% from 1800 microg l(-1) h to 2700 microg l(-1) h (P = 0.04, median increase: 900 microg l(-1) h; 2.5 and 97.5 percentile: 500-1300), and 56% for the peak concentration in plasma (from 550 to 870 microg l(-1), P = 0.04; median increase: 320 microg l(-1) h, 2.5 and 97.5 percentile: 60-450 microg l(-1)). In the ritonavir group, there were no detectable changes in the pharmacokinetic parameters on addition of fluconazole. CONCLUSIONS: Because of the favourable safety profile of saquinavir, dose adjustments are probably not necessary with concomitant use of fluconazole, as is the case for ritonavir.