Lopinavir Concentrations Research Articles

Brief Report: Significant Decreases in Both Total and Unbound Lopinavir and Amprenavir Exposures During Coadministration: ACTG Protocol A5143/A5147s Results.

This secondary analysis explored changes in protein-unbound concentrations of lopinavir and amprenavir when coadministered in HIV-infected subjects. Total and unbound pharmacokinetic parameters were calculated and compared between subjects receiving each agent alone and coadministration. When coadministered, unbound and total concentrations decrease. Coadministration significantly increased lopinavir unbound clearance, while significant changes in fraction unbound (fu) were not detected. For amprenavir, significant increases in fu and unbound clearance occurred with coadministration. This demonstrates the complex nature of drug-drug interactions between highly protein-bound, CYP-metabolized drugs, and the need to measure unbound concentrations in disease states such as hepatitis C, where such agents are coadministered.

Altered Oligodendrocyte Maturation and Myelin Maintenance: The Role of Antiretrovirals in HIV-Associated Neurocognitive Disorders.

Despite effective viral suppression through combined antiretroviral therapy (cART), approximately half of HIV-positive individuals have HIV-associated neurocognitive disorders (HAND). Studies of antiretroviral-treated patients have revealed persistent white matter abnormalities including diffuse myelin pallor, diminished white matter tracts, and decreased myelin protein mRNAs. Loss of myelin can contribute to neurocognitive dysfunction because the myelin membrane generated by oligodendrocytes is essential for rapid signal transduction and axonal maintenance. We hypothesized that myelin changes in HAND are partly due to effects of antiretroviral drugs on oligodendrocyte survival and/or maturation. We showed that primary mouse oligodendrocyte precursor cell cultures treated with therapeutic concentrations of HIV protease inhibitors ritonavir or lopinavir displayed dose-dependent decreases in oligodendrocyte maturation; however, this effect was rapidly reversed after drug removal. Conversely, nucleoside reverse transcriptase inhibitor zidovudine had no effect. Furthermore, in vivo ritonavir administration to adult mice reduced frontal cortex myelin protein levels. Finally, prefrontal cortex tissue from HIV-positive individuals with HAND on cART showed a significant decrease in myelin basic protein compared with untreated HIV-positive individuals with HAND or HIV-negative controls. These findings demonstrate that antiretrovirals can impact myelin integrity and have implications for myelination in juvenile HIV patients and myelin maintenance in adults on lifelong therapy.

Expedient screening for HIV-1 protease inhibitors using a simplified immunochromatographic assay.

A colloidal gold-based immunochromatographic (IC) strip test was developed and validated for the detection of HIV-1 protease (HIV-PR) activity and inhibitory effect of HIV-PR inhibitors (PIs). It is a unique 'two-step' process requiring the combination of proteolysis of HIV-PR and an immunochromatographic reaction. Monoclonal antibodies to the free C-terminus of HIV matrix protein (HIV-MA) conjugated to gold particles and a monoclonal antibody against intact and cleaved forms of the HIV-MA are immobilized on the 'Test'-line of the IC strip. Using lopinavir, a potent HIV protease inhibitor, the IC-strip was optimized to detect inhibitory activity against HIV-protease. At a lopinavir concentration of 1000ng/mL (its suggested minimum effective concentration), a HIV-PRH6 concentration of 6mg/mL and incubation period of 60min were the optimal conditions. A preliminary comparison between a validated high-performance liquid chromatography assay and the IC-strip to semi-quantify HIV protease inhibitor concentrations (lopinavir and atazanavir) demonstrated good agreement. This simplified method is suitable for the rapid screening of novel protease inhibitors for future therapeutic use. Moreover, the IC strip could also be optimized to semi-quantify PIs concentrations in plasma samples.

HIV-1 CNS in vitro infectivity models based on clinical CSF samples.

The concentration of antiretrovirals in CSF is often utilized as a surrogate for CNS drug exposure. This measurement does not consider pharmacodynamic or combinative effects of ART. We have developed a novel endpoint measurement to assess antiretroviral activity of CSF from subjects on ART. CSF samples were obtained from patients receiving tenofovir/emtricitabine (245/200 mg once daily) with either rilpivirine (25 mg once daily) or lopinavir/ritonavir/maraviroc (400/100/150 mg twice daily) and HIV-uninfected controls. Antiviral activity of ART-containing CSF was assessed in cell cultures using PBMCs and neuro-derived glial (U87) and astrocyte (373) cell lines. Infectivity model half-maximal inhibitory concentration (IMIC50) values were calculated and expressed as -log2IMIC50. Results were correlated with CSF antiretroviral concentrations. Compared with controls, CSF from both ART studies demonstrated in vitro antiretroviral activity in all models. CSF antiretroviral activity of patients on lopinavir/ritonavir/maraviroc was significantly greater than that of patients on rilpivirine [-log2IMIC50 (95% CI) 4.82 (4.74-4.89) versus 3.43 (3.33-3.54) in PBMCs, 3.06 (2.98-3.15) versus 2.56 (2.46-2.65) in U87 cells and 6.00 (6.11-5.88) versus 4.90 (5.09-4.72) in 373 cells, respectively]. Positive correlations were observed for individual CSF antiretroviral activity in different cellular models with CSF concentrations of rilpivirine (P = 0.040 in 373 cells) and lopinavir (P = 0.048 in 373 cells), but not maraviroc. Antiviral activity of CSF from patients on ART was successfully calculated and was greater with a regimen containing four active drugs compared with three active drugs. The use of neuro-derived cell lines alongside PBMCs to assess the effect of ART on CSF may act as a useful future clinical research tool.

The pharmacokinetics of lopinavir/ritonavir when given with isoniazid in South African HIV-infected individuals

Isoniazid preventive therapy is recommended in patients on antiretroviral treatment (ART) with latent tuberculous infection to prevent progression to active tuberculosis disease. Isoniazid (INH) inhibits cytochrome (CY) P3A4, which metabolises lopinavir (LPV). The administration of INH may cause higher LPV concentrations, which may increase LPV toxicity. LPV bioavailability is increased by co-formulated ritonavir (r), which may enhance the interaction of INH on LPV. We studied the effect of INH on LPV concentrations by administering INH for 7 days and performing intensive pharmacokinetic sampling in 16 human immunodeficiency virus infected patients established on LPV/r-based ART. INH did not significantly increase steady-state LPV area under the plasma concentration-time curve calculated for the 12 h-dosing interval.

Using Lopinavir Concentrations in Hair Samples to Assess Treatment Outcomes on Second-Line Regimens Among Asian Children.

We conducted a prospective monitoring study to determine whether antiretroviral (ARV) levels in hair of Asian children on second-line protease inhibitor-based ARV therapy (ART) are associated with virologic failure (VF), compared to plasma drug levels and self-reported adherence. HIV-infected Asian children on second-line ART regimens were enrolled into a longitudinal cohort. Traditional adherence measures, plasma, and hair samples were collected 24 weeks after study enrollment. Hair ARV levels were determined via liquid chromatography/tandem mass spectrometry. Among 149 children on lopinavir/ritonavir-based regimens, 47% were female; the median [interquartile range (IQR)] age was 10.3 (7.9-13.3) years. The median CD4% was 26% (IQR 21.7-32.1%) and the median CD4 cell count 754 (IQR 596-1,013) cells/mm(3). The median duration of lopinavir-based ART prior to week 24 of the study was 2.9 (IQR 1.6-4.2) years. Adherence was >95% in 91% (135/148) by visual analogue scale and 89% (129/145) by pill count. The median lopinavir hair concentrations were 5.43 (IQR 3.21-9.01) ng/mg in children with HIV RNA >1,000 copies/ml and 9.96 (IQR 6.51-12.31) ng/mg in children with HIV RNA <1,000 copies/ml (p = 0.003). Plasma trough and lopinavir hair concentrations were not statistically significantly correlated (Pearson's correlation coefficient 0.20; p = 0.13). Increasing lopinavir hair concentrations in quartiles were strongly associated with virologic success (odds ratios ≥4.0, overall p = 0.02), while self-reported adherence, pill count, and plasma lopinavir levels were not. Based on this first report of hair ARV concentrations and virologic outcomes in children, ARV hair concentrations, representing longer-term adherence, may be useful to identify children at risk for VF.

Population approach to analyze the pharmacokinetics of free and total lopinavir in HIV-infected pregnant women and consequences for dose adjustment.

The aims of this study were to describe the unbound and total lopinavir (LPV) pharmacokinetics in pregnant women in order to evaluate if a dosing adjustment is necessary during pregnancy. Lopinavir placental transfer is described, and several genetic covariates were tested to explain its variability. A total of 400 maternal, 79 cord blood, and 48 amniotic fluid samples were collected from 208 women for LPV concentration determinations and pharmacokinetics analysis. Among the maternal LPV concentrations, 79 samples were also used to measure the unbound LPV concentrations. Population pharmacokinetics models were developed by using NONMEM software. Two models were developed to describe (i) unbound and total LPV pharmacokinetics and (ii) LPV placental transfer. The pharmacokinetics was best described by a one-compartment model with first-order absorption and elimination. A pregnancy effect was found on maternal clearance (39% increase), whereas the treatment group (monotherapy versus triple therapy) or the genetic polymorphisms did not explain the pharmacokinetics or placental transfer of LPV. Efficient unbound LPV concentrations in nonpregnant women were similar to those measured during the third trimester of pregnancy. Our study showed a 39% increase of maternal total LPV clearance during pregnancy, whereas unbound LPV concentrations were similar to those simulated in nonpregnant women. The genetic polymorphisms selected did not influence the LPV pharmacokinetics or placental transfer. Thus, we suggest that the LPV dosage should not be increased during pregnancy.

A rapid spin through oil results in higher cell-associated concentrations of antiretrovirals compared with conventional cell washing.

Determination of cell-associated antiretroviral drug concentrations is necessary for research into reservoirs of HIV. Variation exists in cell-associated drug concentrations among research groups. One cause for this may be washing cells during processing. We explored spinning cells through oil to minimize this variability. Raltegravir, atazanavir, darunavir, efavirenz, lopinavir and ritonavir concentrations were assessed in CEM.ss T cells washed with HBSS and oil-spun cells. Oil-spun cells had significantly higher concentrations for all drugs compared with samples washed with HBSS. The decline in cell-associated drug concentrations with saline washes compared with a single spin through oil shows the utility of a spin through oil. Oil centrifugation results in high cell-associated drug concentrations, and can be done in a fast, efficient manner.

Antiretroviral Drugs in Meconium: Detection for Different Gestational Periods of Exposure

To determine whether antiretroviral (ARV) medications can be detected in meconium from second or third trimester, labor and delivery (L&D), or postnatal exposures. Twenty ARV medications were quantified by liquid chromatography-tandem mass spectrometry in 598 meconium samples from uninfected infants born to pregnant women with HIV enrolled in the Pediatric HIV/AIDS Cohort Study. ARV detection in meconium following third trimester exposure was 85.7%-94.4% for all ARVs except stavudine (0%, n = 2), likely because of low doses and a high limit for quantification. Of 107 samples with some second trimester only ARV exposures, meconium was positive for only lopinavir, tenofovir, or efavirenz in 11.8%-14.3% of exposed neonates; administration of these ARVs occurred between gestational weeks 25-28 in the positive samples. Days without lopinavir or tenofovir before delivery significantly correlated with decreasing concentrations of lopinavir and tenofovir in meconium. Tenofovir and lamivudine concentrations significantly correlated with increasing gestational age among infants with continuous second and third trimester exposure. Zidovudine given during L&D or for neonatal prophylaxis was detected in 95.1% and 94.6% of meconium samples, respectively. Changes in ARV treatments during pregnancy offered a unique opportunity to investigate ARV detection in meconium. ARVs in meconium primarily reflect third trimester ARV exposures, although 6 of 107 second trimester only exposures were detected. Zidovudine administration during L&D was detected in meconium indicating potential urine contamination or rapid incorporation into meconium. These data will improve interpretation of meconium drug test results.

Polyinosinic/Polycytidylic Acid-mediated changes in maternal and fetal disposition of lopinavir in rats.

Maintenance of optimal lopinavir (LPV) concentration is essential for effective antiretroviral therapy and prevention of mother-to-child transmission of human immunodeficiency virus. However, little is known about the effects of inflammation on the pharmacokinetics of this protease inhibitor and drug transporter substrate, particularly during gestation. Our objective was to study the effect of polyinosinic/polycytidylic acid [poly(I:C)], a viral mimetic, on key maternal drug transporters, and to examine the effect on maternal and fetal disposition of LPV in rats. Poly(I:C) (5.0 mg/kg i.p.) or saline vehicle was administered to pregnant Sprague-Dawley rats on gestational days 17-18. At 24 hours postinjection, all rats were administered LPV (10 mg/kg i.v.), and plasma and tissues were collected at 5-120 minutes postadministration. Plasma interferon-γ (IFN-γ) levels were measured by enzyme-linked immunosorbent assay, and transporter expression was measured via real-time polymerase chain reaction. Maternal plasma, hepatic, placental, and fetal LPV concentrations were determined by liquid chromatography-tandem mass spectrometry. Administration of poly(I:C) induced IFN-γ plasma levels and downregulated the expression of several important ATP-binding cassette (ABC) drug efflux transporters in the placenta and liver of pregnant rats, compared with controls (P < 0.05). Maternal LPV plasma concentration and area under the concentration-versus-time curve were significantly increased in the poly(I:C) group. Plasma protein binding was also significantly higher in poly(I:C)-treated rats. Pronounced increases in hepatic, placental, and fetal LPV tissue:unbound plasma concentrations were seen in the poly(I:C) group; however, absolute tissue concentrations were not changed. Since the majority of commonly used and clinically important antiretroviral drugs are known to be ABC transporter substrates, inflammation-mediated changes in transporter expression could affect their maternal disposition and fetal exposure.

Anti-HIV Drug-Combination Nanoparticles Enhance Plasma Drug Exposure Duration as Well as Triple-Drug Combination Levels in Cells Within Lymph Nodes and Blood in Primates

HIV patients on combination oral drug therapy experience insufficient drug levels in lymph nodes, which is linked to viral persistence. Following success in enhancing lymph node drug levels and extending plasma residence time of indinavir formulated in lipid nanoparticles, we developed multidrug anti-HIV lipid nanoparticles (anti-HIV LNPs) containing lopinavir (LPV), ritonavir (RTV), and tenofovir (PMPA). These anti-HIV LNPs were prepared, characterized, scaled up, and evaluated in primates with a focus on plasma time course and intracellular drug exposure in blood and lymph nodes. Four macaques were subcutaneously administered anti-HIV LNPs and free drug suspension in a crossover study. The time course of the plasma drug concentration as well as intracellular drug concentrations in blood and inguinal lymph nodes were analyzed to compare the effects of LNP formulation. Anti-HIV LNPs incorporated LPV and RTV with high efficiency and entrapped a reproducible fraction of hydrophilic PMPA. In primates, anti-HIV LNPs produced over 50-fold higher intracellular concentrations of LPV and RTV in lymph nodes compared to free drug. Plasma and intracellular drug levels in blood were enhanced and sustained up to 7 days, beyond that achievable by their free drug counterpart. Thus, multiple antiretroviral agents can be simultaneously incorporated into anti-HIV lipid nanoparticles to enhance intracellular drug concentrations in blood and lymph nodes, where viral replication persists. As these anti-HIV lipid nanoparticles also prolonged plasma drug exposure, they hold promise as a long-acting dosage form for HIV patients in addressing residual virus in cells and tissue.

Long-acting three-drug combination anti-HIV nanoparticles enhance drug exposure in primate plasma and cells within lymph nodes and blood.

Insufficient HIV drug levels in lymph nodes have been linked to viral persistence. To overcome lymphatic drug insufficiency, we developed and evaluated in primates a lipid-drug nanoparticle containing lopinavir, ritonavir, and tenofovir. These nanoparticles produced over 50-fold higher intracellular lopinavir, ritonavir and tenofovir concentrations in lymph nodes compared to free drug. Plasma and intracellular drug levels in blood were enhanced and sustained for 7 days after a single subcutaneous dose, exceeding that achievable with current oral therapy.

CSF LPV concentrations and viral load in viral suppressed patients on LPV/r monotherapy given once daily.

Introduction Plasma trough concentrations of lopinavir (LPV) given as LPV/r 800/200 mg once daily (OD) are reduced in comparison with 400/100 mg twice daily (BID). While OD dosage of LPV/r is sufficient to achieve viral suppression in plasma, data about drug penetration and viral suppression in central nervous system (CNS) is needed, mainly if LPVr is used as maintenance monotherapy strategy in selected patients. The objective of this study was to evaluate CSF HIV-1 RNA and CSF LPV concentrations in patients receiving LPV/r monotherapy OD (LPVrMOD).Material and Methods This is a cross-sectional sub-study within a prospective, open-label pilot simplification study to evaluate the efficacy and safety of LPV/rMOD in virologically suppressed patients previously receiving a BID LPV/r monotherapy regimen (LPV/rMBID), the “Kmon study” (NCT01581853). To assess LPV concentrations and HIV-1 RNA in CSF, a lumbar puncture (LP) was performed in a subgroup of patients after at least one month of LPVrMOD treatment. Plasma-paired samples of all patients were also obtained. HIV-1 RNA was determined by real-time PCR (limit of detection 40 copies/mL). Liquid chromatography-tandem mass spectrometry (Tandem labs, NJ) was used to determine CSF and blood plasma LPV concentrations.Results Nine patients were included. Median (range) age was 48 (34–56) years, median CD4 cell count 672 (252–1,408) cells/mL, median nadir CD4 count 125 (35–537) cells/mL and 40% of subjects were HCV-positive. Before starting LPV/rMOD median time on a LPV/r-containing regimen and on LPV/rMBID were 9 (4–11) years and 15 (7–24) months respectively, median time with undetectable HIV viral load was 5 (3–12) years and 2 patients had a previous documented blip. LP was performed a median of 24 (8–36) weeks after starting LPV/rMOD and 24 (11–28) hours after the last LPV/rMOD dose CSF and plasma HIV RNA was 40 copies/mL in all patients. Median LPV CSF concentration was 9.78 (1.93–78.3) ng/mL, median LPV plasma concentration 1,103 (377–16,700) ng/mL and median LPV CSF/plasma ratio 0.3% (0.1–1.2).Conclusions No CSF viral escape was detected and LPV concentrations were above the IC50 for wtHIV-1 (1.9 ng/mL). However, as concentrations were close to IC50 in some patients, a careful clinical follow up of patients receiving this regimen would be advisable. Larger longitudinal studies will be helpful for a better understanding of the CNS antiviral activity of LPVr monotherapy.

Is it time to revise antiretrovirals dosing? a pharmacokinetic viewpoint.

We document our experience with therapeutic drug monitoring (TDM) of antiretroviral agents (1807 determinations) carried out as day-by-day clinical practice for the optimization of drug dosing in HIV-infected patients. A significant proportion of patients had lopinavir, atazanavir and nevirapine trough concentrations exceeding the upper therapeutic threshold. Further studies are needed to identify good candidates/drugs for TDM, eventually allowing the selection of patients who may benefit from TDM-driven adjustments in antiretrovirals dosage.

Impact of body weight and missed doses on lopinavir concentrations with standard and increased lopinavir/ritonavir doses during late pregnancy

To assess the influence of body weight and missed doses on lopinavir pharmacokinetics with standard and increased doses of lopinavir/ritonavir melt extrusion tablets during late pregnancy. Lopinavir concentration data during the third trimester of pregnancy were pooled from clinical trials in Thailand (NCT00409591) and the USA (NCT00042289). A total of 154 HIV-infected pregnant women receiving either 400/100 mg (standard) or 600/150 mg (increased) twice daily had lopinavir plasma concentration data available. Population parameters were estimated using non-linear mixed-effects regression models. Monte Carlo simulations were performed to estimate the probability of achieving target lopinavir trough concentrations (>1.0 mg/L) with standard and increased doses of lopinavir/ritonavir during pregnancy. The median (range) age, weight and gestational age were 28 years (18-43), 62 kg (45-123) and 33 weeks (29-38), respectively. Body weight influenced lopinavir oral clearance (CL/F) and volume of distribution (V/F). Population estimates of lopinavir CL/F and V/F were 6.21 L/h/70 kg and 52.6 L/70 kg, respectively. Based on simulations, the highest risk of subtherapeutic trough concentrations was for women weighing >100 kg using the standard dose (∼ 7%), while the risk was <2% with the 600/150 mg dose for women weighing 40-130 kg. After a missed dose, 61% of women have lopinavir concentrations below target prior to the next dose with the standard dose compared with 42% with the increased dose. Standard dosing provides adequate lopinavir trough concentrations for the majority of pregnant women but increased doses may be preferable for women weighing >100 kg and with a history of lopinavir/ritonavir use and/or adherence issues.

Determination of total and unbound concentrations of lopinavir in plasma using liquid chromatography-tandem mass spectrometry and ultrafiltration methods.

Lopinavir is an HIV protease inhibitor with high protein binding (98-99%) in human plasma. This study was designed to develop an ultrafiltration method to measure the unbound concentrations of lopinavir overcoming the non-specific binding issue. A liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the determination of total concentrations of lopinavir in plasma was developed and validated, and an adaptation was also optimized and validated for the determination of unbound concentrations. The chromatographic separation was performed with a C18 column (100 mm × 2.1mm i.d., 5 μm particle size) using a mobile phase containing deionized water with formic acid, and acetonitrile, with gradient elution at a flow-rate of 350 μL min(-1). Identification of the compounds was performed by multiple reaction monitoring, using electrospray ionization in positive ion mode. The method was validated over a clinical range of 0.01-1 μg/mL for human plasma ultrafiltrate and 0.1-15 μg/mL in human plasma. The inter and intra-assay accuracies and precisions were between 0.23% and 11.37% for total lopinavir concentrations, and between 3.50% and 13.30% for plasma ultrafiltrate (unbound concentration). The ultrafiltration method described allows an accurate separation of the unbound fraction of lopinavir, circumscribing the loss of drug by nonspecific binding (NSB), and the validated LC-MS/MS methodology proposed is suitable for the determination of total and unbound concentrations of lopinavir in clinical practice.

Successful Anti-Retroviral Therapy in an HIV-Infected Man with Short Gut Syndrome and First Multivisceral Transplant.

Background: Intestinal transplantation in HIV infection has not previously been reported. We describe our approach to achieving and sustaining virologic control in a HIV positive patient with short gut syndrome (SGS) prior to and 12 weeks after multivisceral transplantation (MVT). Methods: Lopinavir concentrations obtained with IRB approval through HIV TDM registry at the University of Buffalo. Raltegravir concentrations obtained commercially. Results: A 37M diagnosed with HIV at time of mesenteric thrombosis in 4/2011 required near complete enterectomy with 68 cm residual duodenum and upper jejunum. HIV viral load (VL) of 1.5x 106 copies(c)/ml dropped 1 log c/ml immediately after bowel removal. Still in care but treatment naïve with VL 19,700 c/ml and CD4 208 cells/ul (36%), he presented 8/2013 with liver failure for MVT evaluation. On 9/9/2013 lopinavir/ritonavir 800/200 mg liquid PO Q8hr and saquinavir 1 gm Q8hr x 4 days were administered to demonstrate absorption. Lopinavir trough of 7.3 ug/ml (goal >1 ug/ml) was achieved. On 10/10/2013 triple therapy (lopinavir/ritonavir 800/200mg Q12hr + enfuvirtide 90mg SC Q12hr, AZT 300mg IV Q12hr) were initiated. VL <20 c/ml was achieved on 11/6/2013. On 11/7/2013 he underwent MVT (stomach, intestine, liver, pancreas, kidney) without induction immunosuppression. On post-MVT day 7, raltegravir 400mg crushed tablet Q12hr, abacavir liquid 300mg Q12hr and lamivudine liquid 50mg daily (renal dose) were initiated by J-tube. Raltegravir 3-hr and trough were 4.57 (goal 0.79-2.27) and 0.5 (goal 0.03-0.12) ug/ml, respectively. HIV VL remained <20 c/ml and CD4 45-83 cells/ul (27-34%) after MVT. He had 3 documented episodes of intestinal rejection. He remained on prophylactic TMP/SMX, azithromycin, and ganciclovir. He experienced prolonged intra-abdominal infection with highly resistant Citrobacter freundii and died at 12 weeks with widespread gram negative septicemia. Conclusions: HIV viral suppression can be achieved with high dose liquid lopinavir/ritonavir in combination with enfuvirtide and IV zidovudine in the setting of SGS. Successful HIV viral suppression can persist after MVT with a standard regimen of abacavir, lamivudine and raltegravir. We recommend therapeutic drug monitoring in this setting.

Amino Acid Prodrugs: An Approach to Improve the Absorption of HIV-1 Protease Inhibitor, Lopinavir

Poor systemic concentrations of lopinavir (LPV) following oral administration occur due to high cellular efflux by P-glycoprotein (P-gp) and multidrug resistance-associated proteins (MRPs) and extensive metabolism by CYP3A4 enzymes. In this study, amino acid prodrugs of LPV were designed and investigated for their potential to circumvent efflux processes and first pass effects. Three amino acid prodrugs were synthesized by conjugating isoleucine, tryptophan and methionine to LPV. Prodrug formation was confirmed by the LCMS/MS and NMR technique. Interaction of LPV prodrugs with efflux proteins were carried out in P-gp (MDCK-MDR1) and MRP2 (MDCK-MRP2) transfected cells. Aqueous solubility studies demonstrated that prodrugs generate higher solubility relative to LPV. Prodrugs displayed higher stability under acidic conditions and degraded significantly with rise in pH. Uptake and transport data suggested that prodrugs carry significantly lower affinity towards P-gp and MRP2 relative to LPV. Moreover, prodrugs exhibited higher liver microsomal stability relative to LPV. Hence, amino acid prodrug modification might be a viable approach for enhancing LPV absorption across intestinal epithelial and brain endothelial cells which expresses high levels of P-gp and MRP2.

Orogastric administration of crushed darunavir tablets for a critically ill patient.

When HIV-positive patients are critically ill and unable to take medications orally, administration of highly active antiretroviral therapy (HAART) becomes challenging. The foremost issue is the lack of parenteral formulations and oral suspensions. Only limited clinical evidence directly addresses the conversion of antiretroviral drugs from the oral to the enteral route. Interruption of HAART is not an acceptable alternative, as this results in HIV viral rebound, immunodeficiency, opportunistic infections, and development of resistance to antiretroviral treatment. Altering the route of administration may affect the plasma concentration of antiretrovirals, which also affects clinical outcomes. For example, as described in one case report, a 28-year-old HIV-positive man with diffuse large B cell–type lymphoma of the duodenum was taking the liquid or powder formulations of lopinavir–ritonavir, abacavir, and lamivudine (at standard adult doses) by oral ingestion, with suppression of the viral load to less than 400 copies/mL. Development of a duodenal obstruction necessitated insertion of a percutaneous jejunal feeding tube (located ≥ 35 cm distal to the ligament of Treitz). HAART was reinitiated via the jejunostomy, leading to HIV viral rebound (to 11 000 copies/mL), undetectable serum concentration of lopinavir, and development of resistance to lamivudine (M184V mutation). Gastric bypass surgery was performed to connect the gastric corpus to the jejunum (20 cm distal from the ligament of Treitz). HAART, including lopinavir–ritonavir (oral liquid), abacavir, and tenofovir, was restarted, and measurement of serum lopinavir concentration 18 weeks later demonstrated adequate absorption of the medication, with HIV viral suppression (to 52 copies/mL). Darunavir is an HIV-1 protease inhibitor recommended for combination HAART regimens for both treatment-naive and treatment-experienced patients. This antiretroviral agent must be administered with ritonavir and food to enhance its pharmacokinetic profile and to ensure adequate antiretroviral activity. The absolute bioavailability of darunavir without ritonavir is only 37%; however, when darunavir is adminstered concurrently with ritonavir, systemic exposure to darunavir increases 14-fold. Limited data suggest adequate absorption of crushed darunavir tablets, both when swallowed and when administered via various enteral tubes. This report describes a case in which crushed darunavir tablets were administered to a critically ill patient through an orogastric feeding tube.

Novel Liquid Chromatography-Tandem Mass Spectrometry Method for Simultaneous Detection of Anti-HIV Drugs Lopinavir, Ritonavir, and Tenofovir in Plasma

For HIV infection, anti-HIV drug combinations are typically used as highly active antiretroviral therapy (HAART), intended to maximize viral suppression. Three drugs used frequently in combination are the protease inhibitors lopinavir and ritonavir and the nucleotide reverse transcriptase inhibitor tenofovir. We have successfully developed a simple, efficient, and sensitive method to simultaneously extract and determine the concentrations of lopinavir, ritonavir, and tenofovir in plasma samples. The plasma extractions were performed using a liquid-liquid extraction followed by protein precipitation of the remaining aqueous layer. The collected fractions were combined, dried, and reconstituted in the mobile phase. The drugs were quantified using liquid chromatography coupled with tandem mass spectrometry. The assay was applied to a study of plasma drug levels in two primates (Macaca nemestrina). The bioanalytical assay was optimized and validated to exhibit a high extraction efficiency and good sensitivity and reproducibility. When the assay was applied in a primate study, all three drugs could be detected in plasma within minutes of subcutaneous dosing. This validated assay will be useful for evaluation of drug concentrations in an efficient, selective, and sensitive manner.