Pharmacokinetic/pharmacodynamic modeling of cortical dopamine concentrations after quetiapine lipid core nanocapsules administration to schizophrenia phenotyped rats.

Schizophrenia (SCZ) response to pharmacological treatment is highly variable. Quetiapine (QTP) administered as QTP lipid core nanocapsules (QLNC) has been shown to modulate drug delivery to the brain of SCZ phenotyped rats (SPR). In the present study, we describe the brain concentration-effect relationship after administrations of QTP as a solution or QLNC to SPR and naïve animals. A semimechanistic pharmacokinetic (PK) model describing free QTP concentrations in the brain was linked to a pharmacodynamic (PD) model to correlate the drug kinetics to changes in dopamine (DA) medial prefrontal cortex extracellular concentrations determined by intracerebral microdialysis. Different structural models were investigated to fit DA concentrations after QTP dosing, and the final model describes the synthesis, release, and elimination of DA using a pool compartment. The results show that nanoparticles increase QTP brain concentrations and DA peak after drug dosing to SPR. To the best of our knowledge, this is the first study that combines microdialysis and PK/PD modeling in a neurodevelopmental model of SCZ to investigate how a nanocarrier can modulate drug PK and PD, contributing to the development of new treatment strategies for SCZ.

Modeling and Simulation as a Tool to Assess Voriconazole Exposure in the Central Nervous System.

Voriconazole is a triazole antifungal used empirically for the treatment of complicated meningitis associated with Cryptococcus neoformans. Biopsy studies show that the drug exhibits adequate brain penetration although levels of cerebral spinal fluid (CSF) are highly variable. Considering that CSF is one of the main surrogates for CNS exposure, the present work proposed the building of a population pharmacokinetic modeling (popPK) model able to describing the exposure achieved by voriconazole in the plasma, interstitial cerebral fluid and CSF of healthy and infected rats. The developed popPK model was described by four compartments, including total plasma, free brain and total CSF concentrations. The following PK parameters were determined: Km = 4.76 mg/L, Vmax = 1.06 mg/h, Q1 = 2.69 L, Qin = 0.81 h-1 and Qout = 0.63 h-1. Infection was a covariate in the Michaelis-Menten constant (Km) and intercompartmental clearance from the brain tissue compartment to central compartment (Qout). Simulations performed with the popPK model to determine the probability of reaching the therapeutic target of fAUC > MIC showed that VRC has sufficient tissue exposure in the interstitial fluid and in the CSF for the treatment of fungal infections in these tissues at prevalent minimum inhibitory concentrations.

In vitro pharmacokinetics/pharmacodynamics modeling and efficacy against systemic candidiasis in Drosophila melanogaster of a bisaryloxypropanamine derivative.

The number of deaths due to systemic fungal infections is increasing alarmingly, which is aggravated by the limitations of traditional treatments and multidrug resistance. Therefore, the research and development of new therapeutic options against pathogenic fungi is an urgent need. To evaluate the fungicidal activity of a synthetic compound, 1,3-bis-(3,4-dichlorophenoxy)propan-2-aminium chloride (2j), through time-kill studies and pharmacokinetics/pharmacodynamics (PK/PD) modeling. The protective effect of the compound was also evaluated using the Drosophila melanogaster minihost model of candidiasis. Mathematical modeling of time-kill data of compound 2j was performed to obtain PD characteristics. Additionally, Toll-deficient D. melanogaster flies were infected with a Candida albicans strain and treated with 2j. We observed that compound 2j demonstrated a time- and dose-dependent fungicidal effect against Candida spp. and dermatophytes, even at low concentrations, and rapidly achieved kill rates reaching the maximum effect in less than one hour. The efficacy of the compound against systemic candidiasis in D. melanogaster flies was comparable to that achieved by fluconazole. These results support the potential of compound 2j as a systemic antifungal agent candidate and serve as a starting point for further studies involving mammalian animal models.

Quantification of neurotransmitters in microdialysate samples following quetiapine dosing to schizophrenia phenotyped rats using a validated LC-MS/MS method.

A versatile method was developed and validated for simultaneous determination of the monoamine neurotransmitters (MNT) dopamine (DA), 3-4-dyhydroxyphenilacetic acid (DOPAC), homovanilic acid (HVA), serotonin (5-HT) and 5-hydroxyindolacetic acid (5-HIAA) in rat brain microdialysate samples using high-performance liquid chromatography tandem mass spectrometry (LC-MS/MS). The method allowed for small sample volume, using positive and negative ionization mode in a single run analysis without any derivatization or cleanup steps. Analytes were quantified at concentrations ranging from 100 ng/mL to 0.05, 10, 0.5, 0.1 or 1 ng/mL (lower limit of quantification, LLOQ) of DA, DOPAC, HVA, 5-HT and 5-HIAA, respectively, showing linearity (r > 0.98), accuracy, and precision (R.S.D ± 15%) according to validation limits accepted by international guidelines. The method was successfully applied for monitoring the concentration changes of MNT in microdialysate samples from medium prefrontal cortex of Wistar rats in a neurodevelopmental model of schizophrenia before and after quetiapine 5 mg/kg i.v. bolus dose administration. No alterations in MNTs were observed in schizophrenia phenotyped rats (SPR) in comparison to the baseline shading a light on the limited response rate to antipsychotic drugs observed in chronic schizophrenic patients.

Semi-Mechanistic Pharmacokinetic Modeling of Lipid Core Nanocapsules: Understanding Quetiapine Plasma and Brain Disposition in a Neurodevelopmental Animal Model of Schizophrenia.

This study investigated plasma and brain disposition of quetiapine lipid core nanocapsules (QLNC) in naive and schizophrenic (SCZ-like) rats and developed a semimechanistic model to describe changes in both compartments following administration of the drug in solution (FQ) or nanoencapsulated. QLNC (1 mg/ml) presented 166 ± 39 nm, low polydispersity, and high encapsulation (93.0% ± 1.4%). A model was built using experimental data from total and unbound plasma and unbound brain concentrations obtained by microdialysis after administration of single intravenous bolus dose of FQ or QLNC to naive and SCZ-like rats. A two-compartment model was identifiable both in blood and in brain with a bidirectional drug transport across the blood-brain barrier (CLin and CLout). SCZ-like rats' significant decrease in brain exposure with FQ (decrease in CLin) was reverted by QLNC, showing that nanocarriers govern quetiapine tissue distribution. Model simulations allowed exploring the potential of LNC for brain delivery. SIGNIFICANCE STATEMENT: A population approach was used to simultaneously model total and unbound plasma and unbound brain quetiapine concentrations allowing for quantification of the rate and extent of the drug's brain distribution following administration of both free drug in solution or as nanoformulation to naive and SCZ-like rats. The model-based approach is useful to better understand the possibilities and limitations of this nanoformulation for drug delivering to the brain, opening the opportunity to use this approach to improve SCZ-treatment-limited response rates.

Quetiapine lipid core nanocapsules restore prepulse inhibition deficits in a neurodevelopmental model of schizophrenia in male and female rats.

Lipid core nanocapsules (LNC) have been extensively studied as a new treatment strategy to improve therapeutic effects of antipsychotic drugs. We investigated the efficacy of quetiapine LNCs (QLNCs) on the poly(i:c) model of schizophrenia in both male and female rats using the pre-pulse inhibition of startle response (PPI) test paradigm after evaluating the outcomes of three different poly(i:c) doses administered to pregnant damns at GD15 on neurodevelopmental outcomes of maternal immune activation (MIA) in adult offspring. QTP solution was not capable of producing a reversal in the sensorimotor gating-disruptive effect caused by the prenatal poly(i:c) exposure. The same dose of QTP given as QLNCs significantly improved PPI-impairment. This is the first study reporting the restoration of the PPI deficits in a neurodevelopmental model of SCZ using LNCs. This is a promising delivery system strategy to improve antipsychotic effects contributing to the development of better SCZ pharmacological treatments.

Time-kill curves of daptomycin and Monte Carlo simulation for the treatment of bacteraemia caused by Enterococcus faecium.

OBJECTIVES: The aim of this study was to investigate the effect of daptomycin against vancomycin-resistant Enterococcus faecium bacteraemia using computer modelling. METHODS: Data obtained in vitro from time-kill curves were evaluated by PK/PD modelling and Monte Carlo simulations to determine the logarithmic reduction in the number of colony-forming units (CFU)/mL over 18 days of daptomycin treatment at 6, 8, and 10 mg/kg doses every 24 or 48 h and with variations in creatinine clearance (CLCR) of 15-29, 30-49, and 50-100 mL/min/1.73 m2. Monte Carlo simulations were performed to evaluate the probability of target attainment (PTA) for an area under the unbound drug concentration-time curve/minimum inhibitory concentration (fAUC/MIC) > 36 at the same doses and CLCR. RESULTS: Static time-kill model was employed to investigate the antibacterial efficacy of constant daptomycin concentrations. The time-kill curve analysis was performed using mathematical modelling based on a Hill coefficient factor. There was an expressive reduction (> 2 Log CFU/mL) over 18 days of daptomycin treatment in 75th percentile of individuals with CLCR of 15-100 mL/min/1.73 m2) with daptomycin 6-10 mg/kg/day, except for daptomycin every 48 h. Using fAUC/MIC > 36, PTA was > 90% at MICs ≤ 2 µg/mL. CONCLUSIONS: Higher daptomycin doses were associated with higher mortality in time-kill curves. The simulations indicated that independent of the CLCR the therapeutic responses of VRE occur with doses of daptomycin ≥ 6 mg/kg/day and daptomycin every 48 h is insufficient to treat enterococcal bacteraemia.

Oral clioquinol is effective in the treatment of a fly model of Candida systemic infection.

BACKGROUND: Clioquinol was used in the 1950s-1970s as antimicrobial but its oral formulations were withdrawn from the market due to suspected neurotoxicity. Currently, there is possibility of repositioning of oral clioquinol formulations. OBJECTIVES: To evaluate the antifungal activity and toxicological parameters of clioquinol and the other two 8-hydroxyquinoline derivatives using alternative animal models and to study the interaction dynamic of clioquinol with Candida albicans. METHODS: We used Toll-deficient Drosophila melanogaster to test the protective effect of 8-hydroxyquinolines against C. albicans infection. Toxicological parameters were investigated in chicken embryo. A mathematical model-based analysis of the time-kill data of clioquinol was performed to obtain pharmacodynamic characteristics. RESULTS: Clioquinol fully protected D. melanogaster from the infection. The 8-hydroxyquinolines did not cause changes in opening of the beak and movement of the chicken embryo; however, clioquinol and compound 2 increased arterial pulsation. Compound 3 was lethal at 1 mg mL-1 . Effective concentration found in modelling indicated that clioquinol was highly effective against C. albicans (0.306 µg mL-1 ) in easily achievable serum levels; clioquinol rapidly achieved kill rate reaching the maximum effect after 13 hours. CONCLUSIONS: These results support the potential of clioquinol to be used as a systemic antifungal agent.

Rapid tools to gain insights into the interaction dynamics of new 8-hydroxyquinolines with few fungal lines.

The combination of tools such as time-kill assay with subsequent application of mathematical modeling can clarify the potential of new antimicrobial compounds, since minimal inhibitory concentration (MIC) value does not provide a very detailed characterization of antimicrobial activity. Recently, our group has reported that the 8-hydroxy-5-quinolinesulfonic acid presents relevant antifungal activity. However, its intrinsic acidity could lead to an ionization process, decreasing fungal cell permeability. To overcome this potential problem and enhance activity, the purpose of this study was to synthesize and evaluate a novel series of hybrids between the 8-hydroxyquinoline core and sulfonamide and to prove their potential using broth microdilution method, obtaining the pharmacodynamic parameters of the most active derivatives combining time-kill studies and mathematical modeling and evaluating their toxicity. Compound 5a was the most potent, being active against all the fungal species tested, with low toxicity in normal cells. 5a and 5b have presented important antibacterial activity against Staphylococcus aureus strain. The EC50 values obtained by combination of time-kill studies with mathematical model were similar to those of MIC, which confirms the potential of compounds. In addition, these derivatives are non-irritant molecules with the absence of topical toxicity. Finally, 5a and 5b are promising candidates for treatment of dermatomycosis and candidiasis.

Population Pharmacokinetic Modeling to Describe the Total Plasma and Free Brain Levels of Fluconazole in Healthy and Cryptococcus neoformans Infected Rats: How Does the Infection Impact the Drug's Levels on Biophase?

PURPOSE: The present work aimed to evaluate the influence of experimental meningitis caused by C. neoformans on total plasma and free brain concentrations of fluconazole (FLC) in Wistar rats. METHOD: The infection was induced by the administration of 100 µL of inoculum (1.105 CFU) through the tail vein. Free drug in the brain was assessed by microdialisys (µD). Blood and µD samples were collected at pre-determined time points up to 12 h after intravenous administration of FLC (20 mg/kg) to healthy and infected rats. The concentration-time profiles were analyzed by non-compartmental and population pharmacokinetics approaches. RESULTS: A two-compartmental popPK model was able to simultaneously describe plasma and free drug concentrations in the brain for both groups investigated. Analysis of plasma and µD samples showed a better FLC distribution on the brain of infected than healthy animals (1.04 ± 0.31 vs 0.69 ± 0.14, respectively). The probability of target attainment was calculated by Monte Carlo simulations based on the developed popPK model for 125 mg/kg dose for rats and 400-2000 mg for humans. CONCLUSIONS: FLC showed a limited use in monotherapy to the treatment of criptoccocosis in rats and humans to value of MIC >8 µg/mL.

Influence of Experimental Cryptococcal Meningitis in Wistar Rats on Voriconazole Brain Penetration Assessed by Microdialysis.

To make advances in the treatment of cryptococcal meningitis, it is crucial to know a given drug's free fraction that reaches the biophase. In the present study, we applied microdialysis (µD) as a tool to determine the free levels reached by voriconazole (VRC) in the brains of healthy and Cryptococcus neoformans-infected rats. The infection was induced by the intravenous (i.v.) administration of 1 × 105 CFU of yeast. The dose administered was 5 mg/kg (of body weight) of VRC, given i.v. Plasma and microdialysate samples were analyzed by liquid chromatography-tandem mass spectrometry (LC-MS/MS) and LC-UV methods. The free brain/free plasma ratio (fT) and population pharmacokinetic (popPK) analyses were performed to evaluate the impact of infection on PK parameters of the drug. The brain penetration ratio showed an increase on brain exposure in infected animals (fThealthy = 0.85 versus fTinfected = 1.86). The structural PK model with two compartments and Michaelis-Menten (MM) elimination describes the VRC concentration-time profile in plasma and tissue simultaneously. The covariate infection was included in volume of distribution in the peripheral compartment in healthy animals (V2) and maximum rate of metabolism (VM ). The levels reached in infected tissues were higher than the values described for MIC of VRC for Cryptococccus neoformans (0.03 to 0.5 µg ml-1), indicating its great potential to treat meningitis associated with C. neoformans.