Determination of saquinavir in human plasma, saliva, and cerebrospinal fluid by ion-pair high-performance liquid chromatography with ultraviolet detection

Antiretroviral bioanalysis methods of tissues and body biofluids

Research in the many areas of HIV treatment, eradication and prevention has necessitated measurement of antiretroviral (ARV) concentrations in nontraditional specimen types. To determine the knowledgebase of critical details for accurate bioanalysis, a review of the literature was performed and summarized. Bioanalytical assays for 31 ARVs, including metabolites, were identified in 205 publications measuring various tissues and biofluids. 18 and 30% of tissue or biofluid methods, respectively, analyzed more than one specimen type; 35-37% of the tissue or biofluid methods quantitated more than one ARV. 20 and 76% of tissue or biofluid methods, respectively, were used for the analysis of human specimens. HPLC methods with UV detection predominated, but chronologically MS detection began to surpass. 40% of the assays provided complete intra- and inter-assay validation data, but only 9% of publications provided any stability data with even less for the prevalent ARV in treatments.

Simple, Rapid and Validated LC Determination of Lopinavir in Rat Plasma and its Application in Pharmacokinetic Studies

Lopinavir is a new specific and potent HIV-1 protease inhibitor. A simple and rapid Reverse Phase High-Performance Liquid Chromatographic method using UV detection was developed and validated for the analysis of lopinavir in rat plasma under isocratic conditions. The method involves a single step protein precipitation technique. The detector response was linear over the concentration range of 250 to 4000 ng mL ⁻¹. High recovery ranging from 97.5 to 101.2 percent was obtained which precludes the use of internal standard. The developed method was validated as per standard guidelines. Validation of the developed method demonstrated accuracy, precision and selectivity of the proposed method. The drug was found to be stable under various processing and storage conditions. This rapid and cost-effective method was successfully applied in the estimation of lopinavir and determination of various pharmacokinetic parameters during post intravenous bolus administration of the drug in rats. The developed method can be suitably employed in preclinical pharmacokinetic evaluation of new formulations designed to improve the bioavailability of lopinavir.

Bioanalytical issues in patient-friendly sampling methods for therapeutic drug monitoring: focus on antiretroviral drugs

Therapeutic drug monitoring is a way to pharmacokinetically guide drug therapy to assure a certain exposure to a drug when this exposure is related to treatment effectiveness or toxicity. Routinely, drug concentrations are measured in plasma obtained by venipuncture. However, venous sampling is difficult in some populations, such as neonates and patients suffering from phlebitis, and there may be logistical challenges, for example when nonhospital-based sampling is warranted (e.g., resource-limited settings). A proper bioanalytical method is crucial for measurements of drug level matrices suitable for patient-friendly drug monitoring. Special attention must be paid to bioanalytical methods in these patient-friendly matrices, since specific matrix-associated issues may have important implications. In this review, we will discuss these issues and give an overview of published bioanalytical methods with a focus on patient-friendly drug monitoring of antiretroviral drugs, where dried blood spots, hair and saliva have been the most important matrices for patient-friendly therapeutic drug monitoring. Furthermore, we will point out considerations for proper assay development and validation.

Critical illness and changes in sensory perception

Impairments of sensory perception that occur during a period of critical care can seriously impact on health and nutritional status, activities of daily living, independence, quality of life and the possibility of recovery. It is emphasized from the outset that sensory losses in critically-ill patients may or may not be related to their current medical condition. The present paper provides an overview of all five senses (vision, hearing, taste, smell and touch) and describes the factors that contribute to sensory losses in critically-ill patients, including medications, medical conditions and treatments and the process of aging itself. Cancer and stroke are two critical illnesses in which profound sensory decrements often occur. Many sensory complaints in patients with cancer are related to alteration in sensory signals caused by damage to the sensory receptors. However, some complaints, such as taste aversions in patients with cancer, are not related to altered sensory physiology per se but to learned aversions that arise during the noxious effects of radiotherapy and chemotherapy. The paper also reviews a study in which the sensory performance (of all five senses) was compared in three groups of elderly subjects: (1) patients who had undergone coronary artery bypass surgery; (2) patients with cardiovascular conditions but with no history of surgery; (3) healthy non-medicated age-matched controls. Performance of patients who had undergone coronary artery bypass surgery was worse than that for the other two groups, with taste and smell losses greater than for the other senses. The study demonstrates that critical illness (e.g. coronary artery bypass surgery) can exacerbate sensory losses in an older cohort.

HPLC quantification of the HIV-1 protease inhibitor saquinavir in brain and testis of mice

A rapid, reliable HPLC method with UV detection (240 nm) was developed and validated for quantitation of saquinavir in mice brain and testis. Saquinavir and the internal standard were isolated from homogenized tissue matrices using liquid-liquid extraction procedure and were then analyzed using an isocratic mobile phase by reversed-phase liquid chromatography. The lower limit of quantification was 50 ng/g for both brain and testis. A linear dynamic range of 50-5000 ng/g for both brain and testis was established. This HPLC method was validated with between-batch precision of 0.5-4.4 and 1.5-5.5% for brain and testis, respectively. The between-batch accuracy was 94.7-105.9% and 97.5-105.0% for brain and testis, respectively. The present method was applied for tissue distribution studies of the novel drug delivery systems of saquinavir in mice.

Simultaneous determination of HIV protease inhibitors amprenavir, atazanavir, indinavir, lopinavir, nelfinavir, ritonavir and saquinavir in human plasma by high-performance liquid chromatography-tandem mass spectrometry

We report a precise and accurate method for simultaneous quantification of protease inhibitors (PIs) amprenavir, atazanavir, indinavir, lopinavir, nelfinavir, ritonavir and saquinavir in plasma. An internal standard was added to samples prior to protein precipitation with acetonitrile followed by addition of ammonium formate buffer. Analysis was by HPLC-MS/MS. Calibration curves were validated over concentration ranges encompassing both subtherapeutic and potentially 'toxic' drug concentrations. Inter- and intra-assay variation were below 11% and PI recovery was above 87%. The bioanalytical method described is successfully applied to measure PI concentrations obtained from clinical pharmacokinetic studies and routine therapeutic drug monitoring (TDM).

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.

Proteinase Activity in Human and Murine Saliva as a Biomarker for Proteinase Inhibitor Efficacy

As molecularly targeted agents reach the clinic, there is a need for assays to detect their presence and effectiveness against target molecules in vivo. Proteinase inhibitors are one example of a class of therapeutic agent for which satisfactory methods of identifying successful target modulation in vivo are lacking. This is of particular importance while these drugs are in clinical trials because standard maximum-tolerated dose-finding studies often are not suitable due to lack of toxicity. Saliva represents a readily accessible bodily fluid that can be repeatedly sampled and used for assaying in vivo effects of systemic drugs. Here we show the development of a simple assay that can be used to measure proteinase activity in saliva and proteinase inhibition after systemic treatment with three different proteinase inhibitors. A variety of gelatinolytic activities present in human and murine saliva have been assayed with a fluorescent dye-labeled substrate and assigned to different proteinase categories by inclusion of specific classes of inhibitors. Treatment of mice with either matrix metalloproteinase inhibitors or a urokinase inhibitor for a period as short as 48 hours results in levels of the drugs that can be detected in saliva by mass spectrometry and concomitant decreases in salivary proteinase activity, thus demonstrating that these inhibitors successfully modulate their targets in vivo.

Determination of saquinavir and ritonavir in human plasma by reversed-phase high-performance liquid chromatography and the analytical error function

Two simple and reproducible high-performance liquid chromatography methods with ultraviolet detection were developed and validated for the quantitation of two protease inhibitors, saquinavir and ritonavir, in human plasma. The same single liquid-liquid extraction procedure with ethyl acetate-hexane (50:50, v/v), reversed-phase column and mobile phase were used. The analyses were accomplished using a Luna C(18) column (150 mm x 4.6mm i.d.) with a C(18) guard column and, the mobile phase consisted of acetonitrile and 70 mM KH(2)PO(4) adjusted to pH 5 with 80 mM Na(2)HPO(4) (46:54, v/v). The wavelength was set at 240 nm for saquinavir and at 210 nm for ritonavir. The retention times were 6.4 min for saquinavir and 8.3 min for ritonavir. The methods were linear over the range of 100-2500 ng/ml for saquinavir and 200-2500 ng/ml for ritonavir. Intra and inter-day precision and accuracy were less than 10.2% for both drugs. Recovery were 90 and 87% for saquinavir and ritonavir, respectively. The drugs were stable at different relevant storage and working conditions. After the validation, their analytical error functions were established as standard deviation (S.D., ng/ml) = 4.84 + 7.14 x 10(-2)C (C is the theoretical concentration value) for saquinavir and S.D. (ng/ml) = 39.98 + 2.40 x 10(-5)C(2) for ritonavir.

Candida albicans secreted aspartyl proteinases in virulence and pathogenesis

Candida albicans is the most common fungal pathogen of humans and has developed an extensive repertoire of putative virulence mechanisms that allows successful colonization and infection of the host under suitable predisposing conditions. Extracellular proteolytic activity plays a central role in Candida pathogenicity and is produced by a family of 10 secreted aspartyl proteinases (Sap proteins). Although the consequences of proteinase secretion during human infections is not precisely known, in vitro, animal, and human studies have implicated the proteinases in C. albicans virulence in one of the following seven ways: (i) correlation between Sap production in vitro and Candida virulence, (ii) degradation of human proteins and structural analysis in determining Sap substrate specificity, (iii) association of Sap production with other virulence processes of C. albicans, (iv) Sap protein production and Sap immune responses in animal and human infections, (v) SAP gene expression during Candida infections, (vi) modulation of C. albicans virulence by aspartyl proteinase inhibitors, and (vii) the use of SAP-disrupted mutants to analyze C. albicans virulence. Sap proteins fulfill a number of specialized functions during the infective process, which include the simple role of digesting molecules for nutrient acquisition, digesting or distorting host cell membranes to facilitate adhesion and tissue invasion, and digesting cells and molecules of the host immune system to avoid or resist antimicrobial attack by the host. We have critically discussed the data relevant to each of these seven criteria, with specific emphasis on how this proteinase family could contribute to Candida virulence and pathogenesis.

Highly sensitive determination of saquinavir in biological samples using liquid chromatography-tandem mass spectrometry

A selective and sensitive method for the determination of the HIV protease inhibitor saquinavir in human plasma, saliva, and urine using liquid-liquid extraction and LC-MS-MS has been developed, validated, and applied to samples of a healthy individual. After extraction with ethyl acetate, sample extracts were chromatographed isocratically within 5 min on Kromasil RP-18. The drug was detected with tandem mass spectrometry in the selected reaction monitoring mode using an electrospray ion source and 2H(5)-saquinavir as internal standard. The limit of quantification was 0.05 ng/mL. The accuracy of the method varied between -1 and +10% (SD within-batch) and the precision ranged from +4 to +10% (SD batch-to-batch). The method is linear at least within 0.05 and 87.6 ng/mL. After a regular oral dose (600 mg) saquinavir concentrations were detectable for 48 h in plasma and were well correlated with saliva concentrations (r(2)=0.9348, mean saliva/plasma ratio 1:15.1). The method is well suited for low saquinavir concentrations in different matrices.

Simultaneous separation of fifteen approved protease and reverse transcriptase inhibitors for human immunodeficiency virus therapy by capillary electrophoresis

In the present investigation, a novel approach towards a complete separation of all 15 protease and reverse transcriptase inhibitors which are currently approved for use in highly active antiretroviral therapy in a single analytical run is presented. The developed method employs an acidic background electrolyte with sodium polyanethol sulfonate (SPAS) as polyanionic electroosmotic flow (EOF) modifier to establish a strong cathodic EOF, sodium dodecyl sulfate (SDS) as pseudostationary selector, and acetonitrile and ethanol as organic modifiers. Separation of the analytes is based on two different mechanisms. The more basic analytes are protonated at the prevailing pH conditions and thus migrate in front of the cathodic EOF, whereas the less basic and neutral analytes interact with the SDS and are retained after the EOF. By optimizing electrolyte pH, the amount of solvents and SDS concentrations in the background electrolyte it is possible to completely separate all compounds of interest.

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.

Quantitative determination of saquinavir from Caco-2 cell monolayers by HPLC-UV. High performance liquid chromatography

The validation and quantitative determination of the protease inhibitor, saquinavir, from confluent Caco-2 monolayers and from aqueous solution is reported. The high performance liquid chromatographic method consisted of an Ultramex 5 C(8) reverse-phase column (250 x 4.6 mm i.d.) and a mobile phase of acetonitrile:water:triethylamine (55:44:1, v/v/v, pH 6.5). Samples were analyzed using an ultraviolet detector at 238 nm, and diltiazem hydrochloride (66 micro g/mL) was used as an internal standard. A linear response over a broad concentration range (0.4-8.0 micro g/mL, r(2) = 0.997) was obtained. The limit of detection and quantitation was set at 0.14 and 0.4 micro g/mL, respectively. Over a 4 day period, the intra-day and inter-day precision ranged from 1 to 7% with a mean of 4%, and from 1 to 2% with a mean of 1.5%, respectively. Bench-top and storage stability of saquinavir was found to be satisfactory. The permeability of saquinavir through Caco-2 monolayers was estimated using this assay.

Simultaneous separation of 11 protease and reverse transcriptase inhibitors for human immunodeficiency virus therapy by co-electroosmotic capillary zone electrophoresis

In the present investigation, a co-electroosmotic capillary zone electrophoretic method is shown for the simultaneous separation of protease inhibitors and reverse transcriptase inhibitors, which are used as antiretroviral therapy drags against the human immunodeficiency virus (HIV). The investigated drugs carry basic amino groups, thus the electrophoretic system takes advantage of an acidic buffer electrolyte. In order to establish a strong cathodic electroosmotic flow (EOF), a poly-anionic surfactant is added to the background electrolyte. Thus, fast migration times due to a co-directional migration of analytes and EOF (co-electroosmotic CE) are obtained. The developed separation system exhibits good selectivities for the investigated compounds and sufficient sensitivity to monitor drug levels in the low ppm range in HIV positive patients who are treated by highly active anitiretroviral therapy.

Simultaneous determination of five HIV protease inhibitors nelfinavir, indinavir, ritonavir, saquinavir and amprenavir in human plasma by LC/MS/MS

A sensitive and rapid liquid chromatography tandem mass spectrometry (LC-MS-MS) method has been developed to measure the levels of five HIV protease inhibitors nelfinavir (NFV), indinavir (IDV), ritonavir (RTV), saquinavir (SQV) and amprenavir (APV) in human plasma. The analytes and internal standard are isolated from plasma by a simple acetonitrile precipitation of plasma proteins followed by centrifugation. LC-MS-MS in positive mode used pairs of ions at m/z of 568.4/330.0, 614.3/421.2, 720.9/296.0, 671.1/570.2 and 505.9/245.0 for NFV, IDV, RTV, SQV and APV, respectively and 628/421 for the internal standard. Two 1/x weighted linear calibration curves for each analyte were established for quantitation with the low curve ranging from 5 to 1000 ng/ml and while the high curve ranging from 1000 to 10,000 ng/ml. Mean inter- and intra-assay coefficients of variation (CVs) over the ranges of the standard curves were less than 10%. The overall recovery of NFV, IDV, RTV, SQV and APV were 88.4, 91.4, 92.2, 88.9 and 87.6%, respectively.

High-performance liquid chromatographic method for the simultaneous determination of the six HIV-protease inhibitors and two non-nucleoside reverse transcriptase inhibitors in human plasma

A selective and sensitive high-performance liquid chromatographic (HPLC) method has been developed for the determination of the six human immunodeficiency virus (HIV)-protease inhibitors (amprenavir, indinavir, lopinavir, nelfinavir, ritonavir, and saquinavir) and the non-nucleoside reverse transcriptase inhibitors (efavirenz and nevirapine) in a single run. After a liquid-liquid extraction with diethyl ether, the six protease inhibitors and the two non-nucleoside reverse transcriptase inhibitors are separated on a Stability RP18 column eluted with a gradient of acetonitrile and phosphate buffer 50 mmol/L pH 5.65. A sequential ultraviolet detection (5-minute sequence set at 240 nm for nevirapine acquisition, 22-minute sequence set at 215 nm for other antiretroviral drugs acquisition followed by a sequence set at 260 nm for internal standard acquisition) allowed for simultaneous quantitation of the six protease inhibitors, nevirapine, and efavirenz. Calibration curves were linear in the range 100 ng/mL to 10,000 ng/mL. The limit of quantitation was 50 ng/mL for all drugs except nevirapine (100 ng/mL). Average accuracy at four concentrations ranged from 88.2% to 110.9%. Both interday and intraday coefficients of variation were less than 11% for all drugs. The extraction recoveries were greater than 62%. This method is simple and shows a good specificity with respect to commonly co-prescribed drugs. This method allows accurate therapeutic monitoring of amprenavir, indinavir, lopinavir, nelfinavir, ritonavir, saquinavir, efavirenz, and nevirapine.

Development of a chromatographic method for the determination of saquinavir in plasma samples of HIV patients

A simple, sensitive and reproducible high-performance liquid chromatographic method for detecting and quantifying saquinavir in human plasma is described. Verapamil was used as internal standard. The method employes a single liquid-liquid extraction step with tert-butil methyl ether followed by chromatography on a Lichrospher 60 Select B C8 reversed-phase column. Ultraviolet detection was used to identify the compounds of interest. The quantitation limit of saquinavir was 1 ng/mL and only 0.5 mL of plasma sample was required for the determination. The average saquinavir recoveries over a concentration range of 2.5-500 ng/mL ranged from 86 to 95%. Precision and accuracy did not exceed 5%.

High-performance liquid chromatography of HIV protease inhibitors in human biological matrices

Methods for HPLC analysis of protease inhibitors (PIs) in human biological matrices were reviewed. Assays have been developed for analysis of single PIs or for simultaneous measurement of multiple PIs in plasma-serum, saliva, cerebrospinal fluid and semen. Liquid-liquid extraction was most often applied for sample pretreatment, but solid-phase extraction and protein precipitation were used as well. Reversed-phase or ion-pair chromatography have been used to separate PIs. Detection of PIs should be sensitive enough for quantitation of plasma concentrations below trough levels of single PIs, or below proposed therapeutic thresholds for PIs. The large majority of assays employs UV detection. As the potential for interferences is large, the selectivity of every method should be evaluated properly. The available high-performance liquid chromatography (HPLC) methods have been applied in clinical pharmacokinetic studies and for therapeutic drug monitoring of PIs. Participation in an interlaboratory quality control program is recommended for every laboratory engaged in the bioanalysis of PIs.

Capillary electrophoretic separation of protease inhibitors used in human immunodeficiency virus therapy

The scope of this work was to investigate the migration behavior of the currently used protease inhibitors for antiretroviral therapy of people infected with the human immunodeficiency virus and to develop a method for their capillary electrophoretic separation and determination. All of the protease inhibitors (indinavir, saquinavir, nelfinavir, amprenavir, and ritonavir) contain at least one basic amino functional group. As a consequence, they can be separated by capillary zone electrophoresis using acidic buffer electrolytes. A fast electroosmotic flow is established in order to increase separation speed, by adding a cationic electroosmotic flow modifier to the electrolyte. After using conventional serum pretreatment procedures it is possible to separate all five protease inhibitors within less than 5 min. In addition, a non-aqueous CE method is also presented which enables the separation of three protease inhibitor compounds within less than 3 min.

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.

Combined hydroxypropyl-beta-cyclodextrin and poly(alkylcyanoacrylate) nanoparticles intended for oral administration of saquinavir

The aim of this study was to prepare and characterize an hydroxypropyl-beta-cyclodextrin-saquinavir inclusion complex with the purpose of incorporating this complex into poly(alkylcyanoacrylate) nanoparticles in order to increase the drug loading. Hydroxypropyl-beta-cyclodextrin-saquinavir complex was characterized by thermal (differential scanning calorimetry), crystallographic (X-ray diffractography) and spectroscopic methods (circular dichroism, H1-NMR). Nanoparticles were prepared by polymerization of alkylcyanoacrylate monomers (isobutyl- and isohexylcyanoacrylate) in a water solution of the complex and further characterized. The apparent solubility of saquinavir was increased 400-fold at pH 7.0 in presence of hydroxypropyl-beta-cyclodextrin owing to the formation of a drug-cyclodextrin complex as demonstrated mainly by 1H NMR and confirmed by other techniques. Saquinavir-loaded nanoparticles could be easily prepared in the presence of a drug-cyclodextrin complex. It was found that large amounts of cyclodextrins remained associated with the particles, resulting in a 20-fold increase in saquinavir loading compared to nanoparticles prepared in the absence of cyclodextrins. This study has shown that the loading in saquinavir of poly(alkylcyanoacrylate) nanospheres could be dramatically improved by simultaneously increasing the apparent solubility of the drug in the preparation medium and the amount of cyclodextrin associated with the particles, making these nanospheres a promising system for oral application.

Determination of serum levels of thirteen human immunodeficiency virus-suppressing drugs by high-performance liquid chromatography

Two high-performance liquid chromatographic methods using UV detection are presented for the determination of two different groups (A and B) of drugs used in the suppression of human immunodeficiency virus (HIV). Group A is comprised of six nucleosidic reverse transcriptase inhibitors, viz. zalcitabine, lamivudine, stavudine, didanosine, zidovudine and ziagen. Group B consists of seven drugs four of which are protease inhibitors (PIs) and three of which are non-nucleosidic reverse transcriptase inhibitors (NNRTIs). The PIs are: indinavir, nelfinavir, saquinavir and ritonavir. The NNRTIs are: nevirapine, delavirdine and efavirenz. Groups A and B require separate aliquots of serum for extraction and must be chromatographed separately.

Sensitive and rapid method for the simultaneous quantification of the HIV-protease inhibitors indinavir, nelfinavir, ritonavir, and saquinavir in human plasma by reversed-phase liquid chromatography

A rapid, sensitive, and specific liquid chromatography method for the simultaneous determination of four protease inhibitors (indinavir, nelfinavir, ritonavir, and saquinavir) in human plasma is described. After a liquid-liquid extraction with terbutyl methyl ether and a sequential washing of the reconstituted sample with hexane, protease inhibitors are separated on a phenyl column using a simple binary mobile phase of ammonium acetate buffer:acetonitrile (48:52) (pH = 7.5) with an ultraviolet detection at 260 nm. The standard curves are linear in the range 0.025-1 microg/mL for saquinavir, 0.1-4 microg/mL for indinavir and nelfinavir, and 0.25-10 microg/mL for ritonavir, with an average recovery ranging from 79% to 99%, and with both low interday and intraday coefficients of variation (<15%). This assay is simple, rapid (15-minute interval between runs) , and useful for therapeutic monitoring of the protease inhibitors on a routine basis.

Simultaneous determination of the five HIV-protease inhibitors: amprenavir, indinavir, nelfinavir, ritonavir, and saquinavir in human plasma by solid-phase extraction and column liquid chromatography

A sensitive and selective liquid chromatographic assay has been developed for the determination of the five protease inhibitors currently approved by the Food and Drug Administration (FDA) (amprenavir, indinavir, nelfinavir, ritonavir, and saquinavir) in a single run. Pretreatment of a 1-mL plasma sample spiked with internal standard was made by a solid-phase extraction procedure using a polymeric reversed-phase sorbent. Liquid chromatography was performed using a narrowbore C18 reversed-phase column and gradient elution. A double ultraviolet detection at 265 nm (amprenavir) and at 210 nm (indinavir, nelfinavir, ritonavir, saquinavir and internal standard) was used. Calibration curves were linear in the range 25-10000 ng/mL and the assay has been validated over the range 25-5000 ng/mL. Average accuracy at four concentrations was in the range of 100.5-104.2% and 96.9-100.5% for within-day and between-day, respectively. The coefficients of variation were less than 10%. Mean absolute recoveries varied from 85.4% (ritonavir) to 98.8% (saquinavir). No metabolite of the protease inhibitors was found to coelute with the drugs of interest or with the internal standard. At this time, among the tested drugs, especially all the presently licensed nucleoside and nonnucleoside reverse transcriptase inhibitors that can be used in combination with the protease inhibitors, none was found to interfere with the assay. This method is now in use in the authors' laboratory for the therapeutic monitoring of the HIV-protease inhibitors.

Saliva as a specimen for monitoring compliance but not for predicting plasma concentrations in patients with HIV treated with indinavir

The presence of the HIV-protease inhibitor indinavir in saliva was analyzed to investigate whether salivary indinavir concentrations are applicable to monitor compliance and/or predict plasma indinavir levels. Fourteen HIV-infected outpatients treated with indinavir and 24 healthy volunteers who ingested a single dose of indinavir were included. Paired plasma and citric-acid-stimulated saliva samples were analyzed by high-performance liquid chromatography (HPLC). Stimulated salivary indinavir concentrations showed a high correlation (r = 0.85, p < 0.01) with corresponding plasma levels. The median saliva/plasma ratio was 65% (P25 50%; P75 94%). The ratios were independent of the plasma concentration; however, a relation with time after ingestion was seen. The unbound fraction of indinavir in plasma was not significantly correlated with the saliva/plasma ratio after stimulated saliva collection, in contrast with a subset of nonstimulated saliva from healthy volunteers, where we did find a significant correlation. Although stimulated salivary indinavir concentrations are highly correlated with plasma concentrations, it is not possible to predict plasma indinavir levels by the salivary concentrations for purposes of therapeutic drug monitoring, due to large interindividual and intraindividual variation. Nevertheless, monitoring compliance by measuring the presence of indinavir in saliva is possible: ingestion of indinavir can be assessed with a sensitivity of 84.8% in the whole dosing interval or with 98.8% between 1 and 6 hours after the last dose, which is comparable with plasma.

Cerebrospinal fluid HIV-1 RNA during treatment with ritonavir/saquinavir or ritonavir/saquinavir/stavudine

OBJECTIVE

To assess the HIV-1-RNA response and drug concentrations in cerebrospinal fluid (CSF) and serum during treatment with saquinavir (SQV)/ritonavir (RTV) or SQV/RTV plus stavudine (d4T) in HIV-1 -infected patients.

DESIGN

A multicentre, open-label, randomized controlled trial.

METHODS

A total of 208 protease inhibitor (PI) and d4T-naive, HIV-1-infected patients were treated with RTV 400 mg twice daily and SQV 400 mg twice daily with or without d4T 40 mg twice daily. Intensification with reverse transcriptase inhibitors was allowed if serum HIV RNA remained above 400 copies/ml after 12 weeks. In 27 volunteers, CSF and serum HIV RNA were measured at baseline, weeks 12 and 48, using the Roche Amplicor and the ultrasensitive assay. In 22 patients, serum and CSF drug concentrations were determined at week 12.

RESULTS

The median baseline serum and CSF HIV-RNA concentrations were 4.81 and 3.21 log10 copies/ml, respectively. A difference in the proportion of patients with a CSF HIV-RNA level below the limit of quantification (< LLQ) after 12 weeks was found: four out of 14 (RTV/SQV) versus 12 out of 13 (RTV/SQV/d4T) (P = 0.001). The same results were found using the ultrasensitive assay. Patients with a baseline HIV-RNA level < LLQ in CSF remained < LLQ, regardless of the treatment regimen. Treatment with RTV/SQV alone was the only independent predictor of a CSF HIV-RNA level > LLQ at week 12 in logistic regression analysis (P = 0.005). CSF RTV and SQV concentrations were < LLQ in most patients.

CONCLUSION

RTV/SQV alone cannot suppress detectable CSF HIV-1-RNA levels to < LLQ after 12 weeks of treatment in the majority of patients. CSF drug concentrations of RTV and SQV < LLQ may explain the suboptimal antiretroviral effect in the CSF.

Determination of twelve antiretroviral agents in human plasma sample using reversed-phase high-performance liquid chromatography

A new high-performance liquid chromatography (HPLC) with UV detection assay was developed for the simultaneous determination of protease inhibitors (PIs), nucleoside and non-nucleoside reverse transcriptase inhibitors (NRTIs, NNRTIs) using a single 1-ml plasma samples. A solid-liquid extraction procedure without internal standard was coupled with two separate reversed-phase HPLC systems; one for the determination of amprenavir, efavirenz, indinavir, nelfinavir, ritonavir, saquinavir (run time=32 min) and one for the determination of abacavir, didanosine, lamivudine, stavudine, nevirapine, zidovudine (run time=40 min). The first requires a mobile phase containing sodium phosphate buffer+ion pair-acetonitrile (50:50, v/v) through a C18 Symmetry column (250x4.6 mm I.D., 5 microm particle size), using variable wavelengths (241, 254 and 261 nm). The second system requires three mobile phases (potassium phosphate buffer+ion pair-acetonitrile) for different elution through a C18 Symmetry Shield column (250x4.6 mm I.D., 5 microm), using a single wavelength (260 nm). Peak-areas are linear; correlation coefficients are better than 0.998 for all compounds, with both inter- and intra-day relative standard deviations lower than 12%. Extraction recoveries are higher than 93% for PIs and NNRTIs and higher than 70% for NRTIs. The method is specific and sensitive and was used to determine trough and peak levels of antiretroviral drugs in HIV infected patients under various combinations of RTIs and PIs.

Simultaneous high-performance liquid chromatographic determination of the antiretroviral agents amprenavir, nelfinavir, ritonavir, saquinavir, delavirdine and efavirenz in human plasma

This article describes a method for the simultaneous determination of four licensed HIV protease inhibitors (amprenavir, nelfinavir, saquinavir and ritonavir) and two novel non-nucleoside reverse transcriptase inhibitors (efavirenz and delavirdine) in human plasma in a single run. Plasma samples (500 microl) were treated by liquid-liquid extraction with methyl tert.-butyl ether. The compounds were separated by reversed-phase liquid chromatography on a C(18) column with spectrophotometric detection at 260 nm. The method is linear over the specific ranges investigated, accurate (inaccuracy <11.7%) and showed intra-day and inter-day precision within the ranges of 0.9-7.0 and 1.9-8.8%, respectively. The six compounds were stable in plasma after 6 months of storage at -20 degrees C and after five freeze-thaw cycles.

Sensitive liquid chromatographic assay for amprenavir, a human immunodeficiency virus protease inhibitor, in human plasma, cerebrospinal fluid and semen

A sensitive bio-analytical assay for amprenavir, a human immunodeficiency virus protease inhibitor, based on reversed-phase liquid chromatography and fluorescence detection, is reported. The analyte is extracted from the matrix, plasma, cerebrospinal fluid (CSF) or semen, with chloroform using propyl-p-hydroxybenzoate as an internal standard. After centrifugation, evaporation of the organic phase and reconstitution in the eluent, the sample is injected into the chromatograph. The analyte is detected spectrofluorometrically at 270 and 340 nm for excitation and emission, respectively. The method has been validated in the 1-1000 ng/ml range for a 50-microl volume of plasma and in the 0.5-50 ng/ml range for a 100-microl volume of CSF and semen. The lower limit of quantification was 0.5 ng/ml in CSF and 1 ng/ml in both plasma and semen. Precision and accuracy both meet the current requirements for a bio-analytical assay and are <15% in the validated ranges. The assay was successfully used to obtain a concentration-time curve of amprenavir in plasma.

Chromatographic and immunochemical approaches to the analysis of the HIV protease inhibitor saquinavir in plasma

The development of the HIV protease inhibitor saquinavir (Ro 31-8959) required a range of analytical methods for its measurement in biological fluids. This paper describes the development of isocratic, reverse-phase HPLC/UV methods for the routine measurement of plasma levels of the drug together with a more sensitive radioimmunoassay. The performance of the two assays is compared with that of an HPLC/MS/MS method previously published and has been shown to be satisfactory, with coefficients of variation of calibration standards and quality control samples within the usual outside limits of +/- 15%. The HPLC/UV method can be routinely applied for concentrations down to 10-20 ng/ml and a lower limit of quantification of 1 ng/ml from 1 ml of human plasma is possible. The radioimmunoassay was developed for the specific measurement of saquinavir concentrations in human, HIV-positive plasma samples and has a lower limit of quantification of 0.5-1.0 ng/ml. Some preliminary findings suggested that it might not be specific in rat plasma and no attempts have been made to quantify any nonclinical samples with this technique. If still greater sensitivity is required, recourse can be made to the HPLC/MS/MS assay.

Simultaneous determination of the HIV protease inhibitors indinavir, amprenavir, saquinavir, ritonavir, nelfinavir and the non-nucleoside reverse transcriptase inhibitor efavirenz by high-performance liquid chromatography after solid-phase extraction

As part of an on-going study on the suitability of a formal therapeutic drug monitoring (TDM) of antiviral drugs for improving the management of HIV infection, a high-performance liquid chromatography method has been developed to quantify simultaneously in plasma five HIV protease inhibitors (PIs) (i.e., indinavir, amprenavir, saquinavir, ritonavir, nelfinavir) and the novel non-nucleoside reverse transcriptase inhibitor efavirenz. After viral inactivation by heat (60 degrees C for 60 min), plasma (600 microl), with clozapine added as internal standard, is diluted 1:1 with phosphate buffer, pH 7 and subjected to a solid-phase extraction on a C18 cartridge. Matrix components are eliminated with 2 x 500 microl of a solution of 0.1% H3PO4 neutralised with NaOH to pH 7. PIs and efavirenz are eluted with 3 x 500 microl MeOH. The resulting eluate is evaporated under nitrogen at room temperature and is reconstituted in 100 microl 50% MeOH. A 40-microl volume is subjected to HPLC analysis onto a Nucleosil 100, 5 microm C18 AB column, using a gradient elution of MeCN and phosphate buffer adjusted to pH 5.15 and containing 0.02% sodium heptanesulfonate: 15:85 at 0 min-->30:70 at 2 min-->32:68 at 8 min-->42:58 at 18 min-->46:54 at 34 min, followed by column cleaning with MeCN-buffer, pH 5.15 (90:10), onto which 0.3% AcOH is added. Clozapine, indinavir, amprenavir, saquinavir, ritonavir, efavirenz and nelfinavir are detected by UV at 201 nm at a retention time of 8.2, 13.0, 16.3, 21.5, 26.5, 28.7 and 31.9 min, respectively. The total run time for a single analysis is 47 min, including the washing-out and reequilibration steps. The calibration curves are linear over the range 100-10,000 ng/ml. The absolute recovery of PIs/efavirenz is always higher than 88%. The method is precise with mean inter-day relative standard deviations within 2.5-9.8% and accurate (range of inter-day deviations -4.6 to +4.3%). The in vitro stability of plasma spiked with PIs/efavirenz at 750, 3000 and 9000 ng/ml has been studied at room temperature, -20 degrees C and +60 degrees C. The method has been validated and is currently applied to the monitoring of PIs and efavirenz in HIV patients. This HPLC assay may help clinicians confronted to questionable compliance, side effects or treatment failure in elucidating whether patients are exposed to adequate circulating drug levels. The availability of such an assay represents an essential step in elucidating the utility of a formal TDM for the optimal follow-up of HIV patients.

Simultaneous HPLC Assay for Quantification of Indinavir, Nelfinavir, Ritonavir, and Saquinavir in Human Plasma

Background: HIV protease inhibitors are recommended as part of combination antiretroviral therapy. Dual protease inhibitor therapy is also being used clinically. Consequently, a simultaneous assay for indinavir, nelfinavir, ritonavir, and saquinavir was developed.

Methods: Indinavir, nelfinavir, ritonavir, and saquinavir were extracted from plasma (250 μL) with methyl-t-butyl ether at basic pH after addition of an internal standard (A-86093). The compounds were separated on a Keystone BetaBasic C4 column (250 × 3 mm i.d.) at 40 °C with a mobile phase of acetonitrile-50 mmol/L ammonium formate buffer, pH 4.1 (52:48, by volume) at a flow rate of 0.5 mL/min. Indinavir, nelfinavir, ritonavir, and the internal standard (A-86093) were detected at 218 nm, and saquinavir was detected at 235 nm. The method was validated by analysis of five triplicate analyses of calibrators along with quality-control samples at three different concentrations prepared in human plasma.

Results: The extraction recovery was 87–92%. Within-run accuracy for quality-control samples was 6–8%, with CVs of 2–8%. Limits of quantification were 40–50 μg/L for indinavir, nelfinavir, and ritonavir, and 20 μg/L for saquinavir. Cross-validation with a liquid chromatography-mass spectroscopy method for saquinavir and nelfinavir was conducted with patient samples. Regression analysis revealed a good correlation (r2 &gt;0.94) between methods. Larger variations at concentrations &gt;4000 μg/L were observed with nelfinavir. Interference with drugs commonly used in AIDS patients was not observed. Pharmacokinetic profiles for two patients on dual protease therapy were determined.

Conclusions: A reliable and rugged simultaneous HPLC assay for four HIV protease inhibitors was developed. The assay method is convenient for clinical laboratories involved in therapeutic drug monitoring for HIV protease inhibitors. The assay has enough sensitivity to conduct pharmacokinetic studies in patients taking more than one HIV protease inhibitor along with other antiretroviral medications.

Anti-HIV effect of saquinavir combined with ritonavir is limited by previous long-term therapy with protease inhibitors

Combination therapy of saquinavir (SQV) and ritonavir (RTV) seems to have a strong antiretroviral effect pharmacokinetically. The purpose of this study was to examine the effectiveness of combined therapy using SQV and RTV in patients previously treated with protease inhibitors (PIs) and to identify the factors compromising the response to such combination therapy. Nineteen HIV-infected Japanese patients participated in this trial between June 1997 and July 1998, and were monitored until November 1998. Patients were treated with SQV (400 mg twice daily) and RTV (300 or 400 mg twice daily). Among the 17 patients who continued such therapy for longer than 3 months, 6 were responders. Among nonresponders, the duration of PI therapy was longer and a higher frequency of preexisting PI resistance viral mutations was detected than in responders. No significant differences were found in previous use of reverse transcriptase inhibitor therapy, CD4+ and CD8+ T cell counts, viral load at baseline, and plasma concentrations of SQV and RTV between responders and nonresponders. Our results suggest that the response to SQV combined with RTV therapy is complicated by previous long-term treatment with PIs, probably owing to multiple PI resistance mutations. Even in patients with a PI-sensitive HIV genotype, however, resistance mutations can develop during therapy and abrogate the effect of high plasma SQV concentrations.

Effect of protease inhibitors on the sense of taste

The purpose of this study was to investigate the taste properties of protease inhibitors which are essential components of drug regimes used to treat human immunodeficiency virus (HIV) infection. In this study, the taste properties of four protease inhibitors (indinavir, ritonavir, saquinavir, and nelfinavir) were investigated in unmedicated HIV-infected patients and healthy controls. Three of the four protease inhibitors (indinavir, ritonavir, and saquinavir) were found to be predominantly bitter (with additional qualities of medicinal, metallic, astringent, sour, and burning). Nelfinavir was found to be relatively tasteless. HIV-infected and uninfected control subjects detected protease inhibitors at similar concentrations, but HIV-infected subjects perceived suprathreshold concentrations as more bitter than controls. Detection thresholds ranged from 0.0061 mM for saquinavir in HIV-infected patients to 0.0702 mM for ritonavir in uninfected control subjects. Suprathreshold studies indicated that protease inhibitors modified the taste perception of a variety of other taste compounds. These results are consistent with clinical findings that protease inhibitors produce taste complaints that can impact patient compliance.

Salvage therapy with regimens containing ritonavir and saquinavir in extensively pretreated HIV-infected patients

OBJECTIVE

To evaluate the efficacy and toxicity of salvage regimens containing ritonavir and saquinavir in patients failing highly active antiretroviral therapy (HAART), and to correlate outcome with plasma concentrations of protease inhibitors.

DESIGN

Prospective, non-randomized interventional study.

SUBJECTS AND METHODS

Thirty extensively pretreated HIV-infected patients with virological failure under HAART were treated with ritonavir (400 mg twice daily) and saquinavir (600 mg twice daily) and at least one reverse transcriptase inhibitor. HIV-RNA, CD4 cell counts and plasma concentrations of protease inhibitors were determined, and patients were monitored for toxicity at monthly intervals.

RESULTS

Six patients showed complete virological success (HIV-RNA <200 copies/ml at week 12) which was sustained for a median follow-up of 6.3 months. Partial virological response (decrease of HIV-RNA of >1 log10 at week 12) was achieved by a further three patients. Patients with a virological response had significantly higher CD4 cell increases than patients without virological response (mean increase at week 12: 66x10(6) cells/l versus 6x10(6) cells/l; P = 0.01). No clinical events were observed during 6 months of follow-up. Neither the use of a non-nucleoside reverse transcriptase inhibitor (NNRTI) nor the number of newly introduced drugs influenced the virological response. Plasma concentrations of protease inhibitors did not statistically differ between patients with and without success. Toxicity included gastrointestinal disturbances, lipid abnormalities and liver dysfunction.

CONCLUSIONS

In extensively pretreated patients, salvage regimens containing ritonavir and saquinavir had only limited and short-term anti-HIV activity and were associated with substantial toxicity. Plasma concentrations of saquinavir were not predictive for virological response.

Simultaneous quantitative determination of the HIV protease inhibitors amprenavir, indinavir, nelfinavir, ritonavir and saquinavir in human plasma by ion-pair high-performance liquid chromatography with ultraviolet detection

A reversed-phase high-performance liquid chromatographic assay for the simultaneous quantitative determination of five HIV protease inhibitors (i.e. amprenavir, indinavir, nelfinavir, ritonavir, and saquinavir) in human plasma is described. Sample pretreatment consisted of solid-phase extraction prior to ion-pair, reversed-phase high-performance liquid chromatography with ultraviolet detection at 210 nm (amprenavir, indinavir and nelfinavir) and 239 nm (saquinavir and ritonavir). For amprenavir, indinavir and saquinavir the method has been validated over the range of 25 ng/ml to 25 microg/ml using a 0.6 ml sample volume. For nelfinavir and ritonavir the method has been validated over the range of 50 ng/ml to 25 microg/ml. The method proved to be accurate, with an average accuracy at four concentrations ranging from 90.6 to 109.2%, and precise, with the within-day and between-day precision ranging from 1.8 to 6.7%, and 0.7 to 7.6%, respectively. The protease inhibitors which can be quantified by using this assay proved to be stable under various conditions. This assay can readily be used in a hospital laboratory for the routine monitoring of plasma concentrations of these protease inhibitors.

Simultaneous determination of ritonavir and saquinavir, two human immunodeficiency virus protease inhibitors, in human serum by high-performance liquid chromatography

The aim of this study was to describe an high-performance liquid chromatographic assay for the simultaneous determination of two HIV protease inhibitors, saquinavir and ritonavir, in human serum. The method involved extraction of ritonavir and saquinavir from serum with the aid of solid-phase extraction C18 cartridges followed by high-performance liquid chromatography with a C8 column and ultraviolet detection set at a wavelength of 240 nm. The assay was linear and has been validated over the concentrations range of 0.5-32 microg/ml for ritonavir and 0.075-4.8 microg/ml for saquinavir, from 600 microl serum extracted. In future, the assay will be used to support human population pharmacokinetic studies, and therapeutic drug monitoring for ritonavir and saquinavir.

The effect of plasma drug concentrations on HIV-1 clearance rate during quadruple drug therapy

OBJECTIVE

To investigate the relationship between exposure to antiretroviral drugs and the initial decline of plasma HIV-1 RNA.

DESIGN

Open-label study in antiretroviral-naive HIV-1 infected patients using a quadruple drug regimen [nelfinavir (NFV), saquinavir (SQV), stavudine, and lamivudine].

METHODS

The elimination rate constant (k) for HIV-1 clearance was calculated during the first 2 weeks of treatment in 29 patients. Exposure to NFV and SQV was quantified on each study visit. Observed NFV and SQV concentrations were related to those expected in a reference population and a concentration ratio was calculated. The median concentration ratios for NFV and SQV, the baseline CD4+ lymphocyte count and baseline log10 HIV-1 RNA were correlated with k.

RESULTS

A significant positive correlation was observed between k and the median NFV (P = 0.001) or SQV concentration ratio (P = 0.016) in univariate analysis. In multivariate analyses, the median NFV concentration ratio remained significantly correlated with k.

CONCLUSIONS

The variation in the rate of decline of plasma HIV-1 RNA between patients after the initiation of a quadruple drug regimen could be explained by differences in exposure to NFV or SQV. Determination of k could be used to optimise further antiretroviral drug therapy and may be a first tool to assess antiretroviral activities of new or increasing doses of drugs administered in combination regimens. Furthermore, our data suggest that exposure to antiretroviral drugs should be incorporated in mathematical models to describe HIV-1 dynamics in more detail.

High-performance liquid chromatographic determination of ritonavir in human plasma, cerebrospinal fluid and saliva

A simple, ion-pair high-performance liquid chromatographic method has been developed and validated for the quantitative determination of the HIV protease inhibitor ritonavir in human plasma, cerebrospinal fluid and saliva. Sample pretreatment consisted of precipitation of proteins with acetonitrile prior to high-performance liquid chromatography with ultraviolet detection at 239 nm. The method has been validated over the range of 50 ng/ml to 50 microg/ml with use of 100-microl volumes of sample. The currently described assay has been used successfully for the analysis of ritonavir in plasma, cerebrospinal fluid and saliva in HIV-1 infected patients.