Simultaneous determination of 2',3'-dideoxyinosine and the active metabolite, 2',3'-dideoxyadenosine-5'-triphosphate in human peripheral-blood mononuclear cell by HPLC-MS/MS and the application to cell pharmacokinetics.

A specific and reliable HPLC-MS/MS method was developed and validated for the simultaneous determination of 2',3'-dideoxyinosine (ddI) and the active metabolites, 2',3'-dideoxyadenosine-5'-triphosphate (ddA-TP) in human peripheral-blood mononuclear cell for the first time. The analytes were separated on a HILIC column (100mm×2.1mm, 1.7µm) and a triple-quadrupole mass spectrometry equipped with an electrospray ionization (ESI) source was used for detection. The cell homogenates sample was prepared by the solid phase extraction. The calibration curves were linear over a concentration range of 0.5-200.0ng/mL for ddI and 0.25-100.0ng/mL for ddA-TP. The intra-day and inter-day precision was less than 15% and the relative error (RE) were all within ±15%. The validated method was successfully applied to assess the disposition characteristics of ddI and support cell pharmacokinetics after the patients with AIDS were orally administrated with ddI and tenofovir disoproxyl fumarate (TDF).

Efavirenz Capsule Sprinkle and Liquid Formulations With Didanosine and Emtricitabine in HIV-1-infected Infants and Children 3 Months to 6 Years of Age: Study AI266-922.

BACKGROUND: AI266-922 was an open-label, dose-ranging study that assessed the pharmacokinetics, safety and efficacy of efavirenz (EFV) in children (3 months to 6 years). METHODS: Antiretroviral-naïve and antiretroviral-experienced HIV-1-infected children received once-daily EFV as oral solution or capsule sprinkle plus didanosine and emtricitabine (FTC). Pharmacokinetic analyses were undertaken at week 2 and repeated at weeks 10 and 18 after an EFV dose change or switch from oral solution to capsule sprinkle. RESULTS: Thirty-seven subjects were treated. EFV area under the plasma concentration-time curve over 1 dosing interval from time 0 to 24 hours postdose values were generally suboptimal (<110 µM × h) in subjects younger than 3 years treated with oral solution; these subjects switched to capsule sprinkle. Twenty of 21 subjects younger than 3 years treated with capsule sprinkle achieved an EFV area under the plasma concentration-time curve over 1 dosing interval from time 0 to 24 hours postdose value >110 µM × h, although higher initial doses were administered in this age group. Interpatient variability in EFV exposure was high. By week 48, 77.8% and 63.0% of subjects achieved HIV-RNA <400 and <50 copies/mL, respectively. Median changes in log10 HIV-RNA and CD4 percentage from baseline were -3.18 copies/mL and +6%, respectively. Two (5.4%) patients discontinued because of adverse events (AEs). Serious AEs occurred in 20 (54.1%) subjects. Common AEs were diarrhea (49%), nasopharyngitis (35%) and pneumonia (30%). Overall, 43% of subjects with suboptimal EFV exposure at week 2 developed resistance. CONCLUSIONS: Once-daily EFV, given as capsule sprinkle, achieved target exposures in this study although doses were 2-3 times higher than Food and Drug Administration-approved doses for children younger than 3 years. These data are useful for dose selection modeling and simulation; however, Food and Drug Administration-approved doses should be used clinically. EFV + didanosine + FTC was efficacious with no new pediatric safety findings reported.

In vivo absorption of didanosine formulated in pellets composed of chitosan microspheres.

The in vivo absorption of didanosine was studied, focusing on the performance of a novel pharmaceutical formulation for didanosine, composed of chitosan granules containing didanosine incorporated in chitosan microspheres. This novel formulation is aimed at oral administration in AIDS therapy. The experimental results in male adult dogs showed controlled delivery of didanosine along 36 h, with a 2-fold increase in the absorption time of didanosine compared to the commercial granules, gastro-resistant didanosine and tablets. The higher absorption is due to adhesion to the intestinal membrane, improving absorption through increase of residence time, permeation and release. Furthermore, the novel formulation facilitates handling and deglutition, especially in the elderly and children, as well as enhances the taste and reduces the frequency of doses and collateral effects associated with a high concentration of the buffer agents usually used in other formulations.

Novel oleic acid derivatives enhance buccal permeation of didanosine.

The aim of this study was to explore the potential of novel oleic acid (OA) derivatives as buccal permeation enhancers for the delivery of didanosine (ddI). The OA derivatives, i.e. ester derivative (OA1E), the dicarboxylic acid derivative (OA1A) and the bicephalous dianionic surfactant (OA1ANa) were synthesized and their effects were compared to the parent OA. OA, OA1E, OA1A and OA1ANa at 1% w/w all showed potential for enhancing the buccal permeability of ddI with enhancement ratio (ER) of 1.29, 1.33, 1.01 and 1.72, respectively. OA1ANa at 1% w/w demonstrated the highest flux (80.30 ± 10.37 µg cm(-2 )h), permeability coefficient (4.01 ± 0.57 × 10(-3) cm h(-1)) and ER (1.72). The highest flux for ddI (144.00 ± 53.54 µg cm(-2 )h) was reported with OA1ANa 2% w/w, which displayed an ER of 3.09 more than that with ddI alone. At equivalent concentrations, OA1ANa (ER = 3.09) had a significantly higher permeation-enhancing effect than its parent OA (ER = 1.54). Histomorphological studies confirmed that OA1ANa at all concentrations (0.5, 2.0 and 6.0% w/w) had no adverse effects on the mucosae. Morphological changes such as vacuoles formation and increased intercellular spaces were attributed to the buccal permeation-enhancing effect of OA1ANa. This study demonstrated the potential of novel OA derivatives as buccal permeation enhancers. OA1ANa at 2% w/w was also identified as the optimal novel OA derivative to widen the pool of fatty acid derivatives as chemical permeation enhancers for buccal drug delivery.

Comparative buccal permeability enhancement of didanosine and tenofovir by potential multifunctional polymeric excipients and their effects on porcine buccal histology.

This study identified and compared the buccal permeability properties of antiretroviral drugs, didanosine (ddI) and tenofovir (TNF), and the permeability effects of polymeric excipients - i.e. carboxymethylcellulose (CMC), sodium alginate (SA), polyacrylic acid (PAA) and polyethylene glycol (PEG) - as potential multifunctional excipients for buccal drug delivery. Permeation studies across porcine buccal mucosa were performed and the drug was quantified using UV spectrophotometry. The mean flux for both ddI (113-181 µg/cm(2)h) and TNF (40-102 µg/cm(2)h) increased linearly with increasing donor concentration. All polymeric excipients improved permeability of TNF while only PEG was effective for ddI. Permeability enhancement ratios at 20 mg/mL for ddI and TNF were 1.63 and 1.74, respectively, using PEG (0.5% w/v) and CMC (0.5% w/v), respectively. The maximum enhancement ratio of 2.13 for TNF was achieved with 4% w/v PEG. Light and transmission electron microscopy revealed no significant loss in cellular integrity of mucosa treated with either TNF or ddI alone or when coupled with PEG as a polymeric enhancer. Histomorphological observations correlated with flux values obtained for TNF and ddI alone, as well as with PEG's effects on drug mass flux. TNF and ddI have demonstrated buccal delivery potential. Selective polymeric excipients provide an effective means to increase their penetration and may serve as potential formulation multifunctional excipients in a delivery system for delivery via the buccal route.

24-Month adherence, tolerance and efficacy of once-a-day antiretroviral therapy with didanosine, lamivudine, and efavirenz in African HIV-1 infected children: ANRS 12103/12167.

BACKGROUND: There is no data on long-term benefit of once-a-day antiretroviral therapy (ART) with combination of DDI, 3TC and EFV to allow its use in future therapeutic strategies. OBJECTIVES: To assess 24-month immuno-virological, adherence, tolerance, and effectiveness of a once-a-day ART with DDI, 3TC and EFV. METHODS: A phase 2 open trial including 51 children aged from 30 months to 15 years, monitored a once-a-day regimen for 24 months from 2006 to 2008 in the Departement de Pediatrie du CHUSS, at Bobo-Dioulasso in Burkina Faso. We tested immunological and virological response, adherence, tolerance and resistance of the treatment. RESULTS: Children with CD4 >25% at 24 months were 67.4% (33/49) CI 95% [54%, 80%]. The proportion of children with viral plasma RNA <300 cp / ml at 24 months of treatment was 81.6 % (40/49) CI [68.0% 91.2%]. Good adherence was obtained with more than 88% adherence > 95% over the 24 months. Drugs were well tolerated. CONCLUSIONS: Given the limited number of antiretroviral drugs available in Africa and the inadequacy of laboratory monitoring in support program, once-a-day treatment and especially the DDI-based combination strategies could be an attractive operational option.

A novel pharmacokinetic approach to predict virologic failure in HIV-1-infected paediatric patients.

OBJECTIVE: The objective of this study was to develop in children an HIV dynamic model able to predict simultaneously the viral load and CD4 lymphocyte evolutions, and to take into account, through a composite inhibition score, the relative contribution of each drug of the combination efavirenz-didanosine-lamivudine and use this score as a predictor of treatment failure in a multidrug therapy. DESIGN: Open phase II trial (BURKINAME - ANRS 12103) registered in the ClinicalTrials.gov database (http://clinicaltrials.gov) with the no. NCT00122538. METHODS: Forty-nine children aged from 2.5 to 15 years were administered once-daily dose of lamivudine, didanosine and efavirenz. The three drugs effect was then characterized by a composite inhibition score combining the effect of each drug, according to their site and mechanism of action and their relative contribution. RESULTS: Efavirenz was the most potent antiretroviral and was responsible for 65% of the total effect, and then didanosine for 23% and lamivudine was the less potent with 12% of the total observed effect. An EC90 for efavirenz was determined (3.3 mg/l). AUC90 was estimated for lamivudine and didanosine: 8.4 and 1.5 mg h/l, respectively. The composite inhibition score was the best predictor of virologic failure compared with the concentrations of each drug taken independently [hazard ratio (HR) 0.6 per 10% increase, 95% confidence interval (CI) 0.41-0.88]. CONCLUSION: The relative contributions of three combined drugs were assessed on plasma viral load and CD4 lymphocyte count kinetics in HIV-1-infected children. Pharmacokinetics targets have been suggested for lamivudine and didanosine. A composite inhibition score has been determined to be a high predictor of treatment failure in a multidrug therapy.

Anti-HIV efficacy and biodistribution of nucleoside reverse transcriptase inhibitors delivered as squalenoylated prodrug nanoassemblies.

Due to their hydrophilic nature, most nucleoside reverse transcriptase inhibitors (NRTIs) display a variable bioavailability after oral administration and a poor control over their biodistribution, thus hampering their access to HIV sanctuaries. The limited cellular uptake and activation in the triphosphate form of NRTIs further restrict their efficacy and favour the emergence of viral resistance. We have shown that the conjugation of squalene (sq) to the nucleoside analogues dideoxycytidine (ddC) and didanosine (ddI) leads to amphiphilic prodrugs (ddC-sq and ddI-sq) that spontaneously self-organize in water as stable nanoassemblies of 100-300 nm. These nanoassemblies can also be formulated with polyethylene glycol coupled to either cholesterol (Chol-PEG) or squalene (sq-PEG). When incubated with peripheral blood mononuclear cells (PBMCs) in vitro infected with HIV, the NRTI-sq prodrugs enhanced the antiviral efficacy of the parent NRTIs, with a 2- to 3-fold decrease of the 50% effective doses and a nearly 2-fold increase of the selectivity index. This was also the case with HIV-1 strains resistant to ddC and/or ddI. The enhanced antiviral activity of ddI-sq was correlated with an up to 5-fold increase in the intracellular concentration of the corresponding pharmacologically active metabolite ddA-TP. The ddI-sq prodrug was further investigated in vivo by the oral route, the preferred route of administration of NRTIs. Pharmacokinetics studies performed on rats showed that the prodrug maintained low amounts of free ddI in the plasma. Administration of (3)H-ddI-sq led to radioactivity levels higher in the plasma and relevant organs in HIV infection as compared to administration of free (3)H-ddI. Taken together, these results show the potential of the squalenoylated prodrugs of NRTIs to enhance their absorption and improve their biodistribution, but also to enhance their intracellular delivery and antiviral efficacy towards HIV-infected cells.

Submicron-size biodegradable polymer-based didanosine particles for treating HIV at early stage: an in vitro study.

Human immunodeficiency viruses (HIV) hide themselves in macrophages at the early stage of infection. Delivering drug in a sustained manner from polymeric nanoparticles in those cells could control the disease effectively. The study was intended to develop poly(d,l-lactic-co-glycolic acid)-based nanoparticles containing didanosine and to observe their uptake by macrophages in vitro. Various physicochemical evaluations related to nanoparticles, such as drug-excipient interaction, surface morphology, particle size, zeta potential, polydispersity index, drug loading, in vitro drug release and nanoparticle-uptake by macrophages in vitro were determined. Homogenising speeds and drug-polymer ratio varied drug loading and polydispersity index of nanoparticles, providing sustained drug release. Dimethyl sulphoxide/polyethylene glycol improved drug loading predominantly. Nanoparticle-uptake by macrophages was concentration dependent. Experimental nanoparticles successfully transported didanosine to macrophages in vitro, suggesting reduction of dose, thus minimising toxicity and side effects. Developed nanoparticle may control HIV infection effectively at an early stage.

Investigating the effect of Aloe vera gel on the buccal permeability of didanosine.

The buccal mucosal route offers several advantages but the delivery of certain drugs can be limited by low membrane permeability. This study investigated the buccal permeability properties of didanosine (ddI) and assessed the potential of Aloe vera gel (AVgel) as a novel buccal permeation enhancer. Permeation studies were performed using Franz diffusion cells, and the drug was quantified by UV spectroscopy. Histomorphological evaluations were undertaken using light and transmission electron microscopy. The permeability of ddI was concentration-dependent, and it did not have any adverse effects on the buccal mucosae. A linear relationship (R² = 0.9557) between the concentrations and flux indicated passive diffusion as the mechanism of drug transport. AVgel at concentrations of 0.25 to 2 %w/v enhanced ddI permeability with enhancement ratios from 5.09 (0.25 %w/v) to 11.78 (2 %w/v) but decreased permeability at 4 and 6 %w/v. Ultrastructural analysis of the buccal mucosae treated with phosphate buffer saline pH 7.4 (PBS), ddI/PBS, and ddI/PBS/AVgel 0.5 %w/v showed cells with normal plasmalemma, well-developed cristae, and nuclei with regular nuclear envelopes. However, cells from 1, 2, and 6 %w/v AVgel-treated mucosae showed irregular nuclear outlines, increased intercellular spacing, and plasmalemma crenulations. This study demonstrates the potential of AVgel as a buccal permeation enhancer for ddI to improve anti-HIV and AIDS therapy.

Papel protector del tratamiento antirretroviral en el deterioro de la función renal en una cohorte de pacientes infectados por el virus de la inmunodeficiencia humana / Protective role of antiretroviral treatment in the impairment of renal function in a cohort of human immunodeficiency virus patients

Fundamento y objetivos: Evaluar los cambios en la función renal en una cohorte de pacientes con infección por el virus de la inmunodeficiencia humana (VIH) y describir cuáles son los factores asociados a su deterioro.Pacientes y método: Estudio transversal prospectivo. El período de seguimiento ha sido de 12 meses. Al inicio del estudio y al cabo de un año se obtuvo el filtrado glomerular (FG). Además, se analizaron datos epidemiológicos, comorbilidades, valores de linfocitos CD4, carga viral (CV) y estadio de sida. Resultados: Se incluyeron un total de 365 pacientes. Estaban con tratamiento antirretroviral de gran actividad (TARGA) 313 pacientes (85%), la media (DE) de linfocitos CD4 era 606 (314) células/mm3 y la CV era indetectable en el 85% de los casos. Al año, se apreció un deterioro medio del FG de 9,7ml/h. Presentaron un descenso del FG > 10ml/h 80 pacientes (21,8%) y mayor de 30ml/h 20 pacientes (5,8%). Se encontró asociación con la edad, tratamiento con didanosina (DDI) y con el sexo masculino (odds ratio [OR] 1,89 e intervalo de confianza del 95% [IC 95%] 0,3-4,08, OR 2,3 e IC 95% 1,9-23, y OR 3,47 e IC 95% 1,6-14,20, respectivamente). Sí hubo asociación entre el hecho de recibir TARGA y presentar un menor deterioro del FG (OR 0,54, IC 95% 0,25-0,8). Conclusiones: Se aprecia un papel protector del tratamiento con TARGA en el deterioro del FG de los pacientes con infección por el VIH. El sexo masculino, la edad y el uso de DDI estuvieron asociados con un mayor deterioro de la función renal. El tenofovir (TDF) y los inhibidores de la proteasa (IP) no se asociaron a un mayor deterioro de la función renal (AU)

Background and objective: To assess changes in renal function in a cohort of patients infected with the human immunodeficiency virus (HIV) and describe which factors are associated with deterioration.Patients and methods: This was a prospective transversal study. The follow-up period was 12 months. Data were collected at baseline and one year including the glomerular filtration rate (GFR). We analyzed epidemiological data, comorbidities, CD4 lymphocytes, viral load, and AIDS status. Results: A total of 365 patients. Three hundred and thirteen (85%) were under highly active antiretroviral therapy (HAART); the median CD4 was 606±314 and the CV was undetectable in 85%. At 1-year, we found a mean deterioration in the GFR of 9.7ml/h. Eighty patients (21.8%) had a fall in GFR > 10ml/h, while in 20 patients (5.8%) it was > 30ml/h. An association was found regarding age, treatment with didanosine (DDI) and males (OR 1.89 95% CI 1.3 to 4.08, OR 2.3 95% CI 1.9 to 23 and OR 3.47 95% CI 1.6 to 14.20 respectively). We found a protective role of being under HAART (OR 0.54, 95% CI, 0.25 to 0.8). Conclusions: There was a protective role of HAART in the deterioration of GFR of patients with HIV infection. Male gender, age and use of DDI were associated with worsening renal function. Tenofovir and protease inhibitors were not associated with further deterioration of renal function (AU)

Combination anti-HIV therapy with the self-assemblies of an asymmetric bolaamphiphilic zidovudine/didanosine prodrug.

Combination anti-HIV therapy is important for AIDS treatment. A bolaamphiphilic prodrug, zidovudine-phosphoryl-deoxycholyl didanosine (ZPDD), was synthesized, combining zidovudine (AZT) and didanosine (ddI) in one molecule. As one lipid derivative of nucleosides, ZPDD showed special solubility with free soluble in chloroform and tetrahydrofuran but was slightly soluble in cyclohexane. The amphiphilicity of ZPDD was shown according to the monolayers at the air-water interface. ZPDD self-assembled to the spherical vesicles in water with 174 nm in size and -31.3 mV of zeta potential. The stability of assemblies depended on pH because the phosphoryl zidovudine group could release hydrogen ions. ZPDD was rapidly degraded to AZT in the plasma and tissues of mice. ZPDD self-assemblies had high anti-HIV activity in vitro with the half effective concentration (EC50) of 5 nM. ZPDD self-assemblies may be targeting macrophages since ZPDD was found in macrophage-rich tissues in vivo and rapidly released AZT in the targeted tissues after intravenous administration to mice. The bioavailability of ZPDD was 90.5% and 30.8% for the intraperitoneal and oral administrations compared with the venous route. The self-assemblies of bolaamphiphilic prodrugs could simultaneously deliver two types of drugs to targeted tissues and would become a promising nanomedicine.

A new nanomedicine based on didanosine glycerolipidic prodrug enhances the long term accumulation of drug in a HIV sanctuary.

New nanomedicines could improve drug accumulation in HIV sanctuaries and ameliorate their antiretroviral efficiency. In this view, we propose herein a combined strategy based on a biomimetic prodrug of ddI and its formulation in well-characterized lipid nanoobjects. The glycerolipidic prodrug of ddI (ProddINP) has been synthesized and its bulk structure was characterized. An appropriate formulation of this prodrug has been designed using a rational approach combining different physicochemical techniques. The high incorporation ratio of the prodrug into dipalmitoylphosphatidylcholine (DPPC) bilayers was determined by DSC. Then two liposome preparation methods were compared, with respect to size, incorporation yield and molecular/supramolecular organization of vesicles. The best liposomal formulation of ProddINP has been checked to keep intact the anti-HIV activity of ddI. This formulation was finally compared to ddI after oral route in rat. The animal experiments evidenced the increase of ddI blood half life (3-fold) and its enhanced accumulation as prodrug form at 24h in numerous organs and especially intestine after administration of ProddINP in comparison with free drug. Finally, the tested liposomal formulation of ProddINP seems to be a promising approach to eradicate HIV infection from intestinal sanctuaries where the virus can concentrate.

Bifunctional peptidomimetic prodrugs of didanosine for improved intestinal permeability and enhanced acidic stability: synthesis, transepithelial transport, chemical stability and pharmacokinetics.

Five peptidomimetic prodrugs of didanosine (DDI) were synthesized and designed to improve bioavailability of DDI following oral administration via targeting intestinal oligopeptide transporter (PepT1) and enhancing chemical stability. The permeability of prodrugs was screened in Caco-2 cells grown on permeable supports. 5'-O-L-valyl ester prodrug of DDI (compound 4a) demonstrated the highest membrane permeability and was selected as the optimal target prodrug for further studies. The uptake of glycylsarcosine (Gly-Sar, a typical substrate of PepT1) by Caco-2 cells could be inhibited by compound 4a in a concentration-dependent manner. The Caco-2 cells were treated with 0.2 nM leptin for enhanced PepT1 expression. The uptake of compound 4a was markedly increased in the leptin-treated Caco-2 cells compared with the control Caco-2 cells, both of which were obviously inhibited by 20 mM Gly-Sar. The K(m) and V(max) values of kinetic study of compound 4a transported by PepT1 in Caco-2 cells were 0.91 mM and 11.94 nmol/mg of protein/10 min, respectively. The chemical stability studies were performed in simulated gastric fluid (SGF), phosphate buffers under various pH conditions, rat tissue homogenates and plasma at 37 °C. The concentrations of DDI could not be detected in the two minutes in SGF. But compound 4a could significantly increase DDI acidic stability, and its t(½) was extended to as long as 36 min in SGF. Compound 4a was stable in pH 6.0 phosphate buffer but could be quickly transformed into DDI in plasma and tissue homogenates. The oral absolute bioavailability of DDI was 47.2% and 7.9% after compound 4a and DDI were orally administered to rats at a dose of 15 mg/kg, respectively. The coadministration with antiacid agent could also suggest that compound 4a was more stable under harsh acidic conditions compared with DDI. Compound 4a bioavailability in rats was reduced to 33.9% when orally co-administered with Gly-Sar (100 mg/kg). The In Vivo bioactivation mechanism of compound 4a was investigated by comparing the levels of DDI and compound 4a in the jugular and portal veins in rats. The plasma concentration of intact compound 4a was very low in portal veins and could hardly be detected in the jugular vein. In conclusion, compound 4a could significantly improve the oral bioavailability of DDI in rats through PepT1-mediated absorption and enhanced acidic stability, followed by rapid and mostly intracellular bioactivation, the majority in the intestinal cells but the minority in the liver. Additionally, the prodrug strategy targeted to intestinal PepT1 could offer a promising strategy to improve oral bioavailability of poorly absorbed didanosine.

Intracellular nucleotide levels during coadministration of tenofovir disoproxil fumarate and didanosine in HIV-1-infected patients.

Studies were conducted to determine if there is a mechanistic basis for reports of suboptimal virologic responses and concerns regarding the safety of regimens containing the combination of tenofovir (TFV) disoproxil fumarate (TDF) and didanosine (ddI) by assessing the pharmacokinetic consequences of coadministration of these drugs on intracellular nucleotides. This was a prospective and longitudinal study in HIV-1-infected patients of adding either TDF or ddI to a stable antiretroviral regimen containing the other drug. Intracellular concentrations of the nucleotide analogs TFV diphosphate (TFV-DP) and ddATP and the endogenous purine nucleotides dATP and 2'-dGTP in peripheral blood mononuclear cells were measured. A total of 16 patients were enrolled into the two study arms and a study extension. Intracellular TFV-DP concentrations (median, 120 fmol/10(6) cells) and ddATP concentrations (range, 1.50 to 7.54 fmol/10(6) cells in two patients) were unaffected following addition of ddI or TDF to a stable regimen containing the other drug. While coadministration of ddI and TDF for 4 weeks did not appear to impact dATP or dGTP concentrations, cross-sectional analysis suggested that extended therapy with ddI-containing regimens, irrespective of TDF coadministration, may decrease dATP and ddATP concentrations. Addition of TDF or ddI to a stable regimen including the other drug, in the context of ddI dose reduction, did not adversely affect the concentration of dATP, dGTP, TFV-DP, or ddATP. The association between longer-term ddI therapy and reduced intracellular nucleotide concentrations and this observation's implication for the efficacy and toxicity of ddI-containing regimens deserve further study.

Strategies to improve efficacy and safety of a novel class of antiviral hyper-activation-limiting therapeutic agents: the VS411 model in [corrected] HIV/AIDS.

BACKGROUND AND PURPOSE: Antiviral hyper-activation-limiting therapeutic agents (AV-HALTs) are a novel experimental drug class designed to both decrease viral replication and down-regulate excessive immune system activation for the treatment of chronic infections, including human immunodeficiency virus (HIV)/acquired immunodeficiency syndrome. VS411, a first-in-class AV-HALT, is a single-dosage form combining didanosine (ddI, 400 mg), an antiviral (AV), and hydroxyurea (HU, 600 mg), a cytostatic agent, designed to provide a slow release of ddI to reduce its maximal plasma concentration (C(max)) to potentially reduce toxicity while maintaining total daily exposure (AUC) and the AV activity. EXPERIMENTAL APPROACH: This was a pilot phase I, open-label, randomized, single-dose, four-way crossover trial to investigate the fasted and non-fasted residual variance of AUC, C(max) and the oral bioavailability of ddI and HU, co-formulated as VS411, and administered as two different fixed-dose combination formulations compared to commercially available ddI (Videx EC) and HU (Hydrea) when given simultaneously. KEY RESULTS: Formulation VS411-2 had a favourable safety profile, displayed a clear trend for lower ddI C(max) (P= 0.0603) compared to Videx EC, and the 90% confidence intervals around the least square means ratio of C(max) did not include 100%. ddI AUC(∞) was not significantly decreased compared to Videx EC. HU pharmacokinetic parameters were essentially identical to Hydrea, although there was a decrease in HU exposure under fed versus fasted conditions. CONCLUSIONS AND IMPLICATIONS: A phase IIa trial utilizing VS411-2 formulation has been fielded to identify the optimal doses of HU plus ddI as an AV-HALT for the treatment of HIV disease.

Is the recommended once-daily dose of lamivudine optimal in West African HIV-infected children?

We aimed in this study to describe lamivudine concentration-time courses in treatment-naïve children after once-daily administration, to study the effects of body weight and age on lamivudine pharmacokinetics, and to simulate an optimized administration scheme. For this purpose, lamivudine concentrations were measured in 49 children after at least 2 weeks of didanosine-lamivudine-efavirenz treatment. A total of 148 plasma lamivudine concentrations were measured, and a population pharmacokinetic model was developed with NONMEM. The influence of individual characteristics was tested using a likelihood ratio test. Children were divided into two groups, according to their pharmacokinetic parameters, thanks to tree regression analysis. For each patient, the area under the curve was derived from estimated individual pharmacokinetic parameters. Different once-daily doses were simulated in each group, to obtain the same exposure in children as the mean effective exposure in adults (8.9 mg/liter.h). A two-compartment model in which the slope of distribution is assumed to be equal to the absorption rate constant adequately described the data. Parameter estimates were standardized for a mean standard body weight using an allometric model. Children were then divided into 2 groups according to body weight: CL/F was significantly higher in children weighing less than 17 kg (1.12 liters/h/kg) than in children over 17 kg (0.95 liters/h/kg; P=0.01). The target mean AUC of 8.9 mg/liters.h was obtained with a 10-mg/kg once-daily lamivudine (3TC) dose for children below 17 kg; the recommended dose of 8 mg/kg seems to be sufficient in children weighing more than 17 kg. These assumptions should be prospectively confirmed.

Interactions between buprenorphine and antiretrovirals: nucleos(t)ide reverse transcriptase inhibitors (NRTI) didanosine, lamivudine, and tenofovir.

To improve outcomes among injection drug users with HIV and/or chronic hepatitis B, it is important to identify drug interactions between antiretroviral and opiate therapies. We report the results of a study designed to examine the interaction between buprenorphine and the nucleos(t)ide reverse transcriptase inhibitors (NRTI) didanosine (ddI), lamivudine (3TC), and tenofovir (TDF). Opioid-dependent, buprenorphine/naloxone-maintained, HIV-negative volunteers (n = 27) participated in two 24-hour sessions to determine (1) pharmacokinetics of buprenorphine alone and (2) pharmacokinetics of both buprenorphine and either ddI, 3TC, or TDF. Among buprenorphine/naloxone-maintained study participants, no significant changes in buprenorphine pharmacokinetics were observed following ddI, 3TC, or TDF administration. Buprenorphine had no significant effect on NRTI concentrations. Concomitant use of buprenorphine with ddI, 3TC, or TDF results in neither a significant pharmacokinetic nor pharmacodynamic interaction.

Intranasal drug delivery of didanosine-loaded chitosan nanoparticles for brain targeting; an attractive route against infections caused by AIDS viruses.

The primary aim of this study was to investigate intranasal (i.n.) administration as a potential route to enhance systemic and brain delivery of didanosine (ddI). A further aim was to investigate the potential use of chitosan nanoparticles as a delivery system to enhance the systemic and brain targeting efficiency of ddI following i.n. administration. Didanosine-loaded chitosan nanoparticles, were prepared through ionotropic gelation of chitosan with tripolyphosphonate anions, and characterized in terms of their size, drug loading, and in vitro release. The nanoparticles were administered i.n. to rats, compared to i.n. and intravenous (i.v.) administration of ddI in solution. The concentrations of ddI in blood, CSF, and brain tissues were analyzed by ultra performance liquid chromatography mass spectroscopy (UPLC/MS). The brain/plasma, olfactory bulb/plasma and CSF/plasma concentration ratios were significantly higher (P < 0.05) after i.n. administration of ddI nanoparticles or solution than those after i.v. administration of didanosine aqueous solution. The ratio of ddI concentration values of the nanoparticles to the solution at 180 min post-i.n. dosing was 2.1 and 1.9 in CSF and brain, respectively. Thus, both the i.n. route of administration and formulation of ddI in chitosan nanoparticles increased delivery of ddI to CSF and brain.

Simultaneous determination of didanosine and its amino acid prodrug, valdidanosine by hydrophilic interaction chromatography coupled with electrospray ionization tandem mass spectrometry: application to a pharmacokinetic study in rats.

A rapid, sensitive and selective ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method with hydrophilic interaction chromatography has been developed and validated for the simultaneous determination of didanosine and valdidanosine (L-valine amino acid ester prodrug of didanosine) in rat plasma. Solid-phase extraction (SPE) column was employed to extract the analytes from rat plasma, with high extraction recovery (>85%) for both didanosine and valdidanosine. The analytes were then separated by hydrophilic interaction chromatography (HILIC column) and detected by a triple-quadrupole mass spectrometry equipped with an electrospray ionization (ESI) source. The method was linear over the concentration ranges of 2-20,000 ng/mL for didanosine and 4-300 ng/mL for valdidanosine. The lower limit of quantitation (LLOQ) of didanosine and valdidanosine was 2 and 4 ng/mL, respectively. The intra-day and inter-day relative standard deviation (RSD) were less than 15% and the relative errors (RE) were all within 15%. Finally, the validated UPLC-MS/MS method was successfully applied to the pharmacokinetic study after either didanosine or valdidanosine orally administrated to the Sprague-Dawley rats.