Drug Concentration-time Curve Research Articles

Abstract 4477: Safety and efficacy of intracarotid administration of temozolomide in a rat model of intracerebral metastasis.

Abstract Purpose: Temozolomide (Temodar; Merck) is an alkylating chemotherapeutic agent used to treat glioblastoma and other brain malignancies. After oral administration, the average brain interstitium to plasma area under the drug concentration-time curve ratio for temozolomide has been reported as approximately 0.2 in animal models and patients. We hypothesized that intra-arterial (IA) drug administration into the internal carotid artery would improve temozolomide delivery to brain tissue, with subsequent increased anti-tumor efficacy. Methods: Athymic nude rats received intracerebral implantation of LX-1 human small cell lung carcinoma cells as a model of chemosensitive brain metastasis, and were studied 10 days after cell implantation when tumors measured 10-30 mm3 in volume. To assess drug delivery, rats received 25 μCi 14C-temozolomide by oral, intravenous (IV), or IA/osmotic blood-brain barrier disruption (BBBD) route of administration (n = 5-7 per group). Radiolabeled drug in tumor and brain was measured 10 min after drug administration by quantitative autoradiography. To assess efficacy, rats received either no treatment or a single treatment with 20 mg/kg temozolomide (∼150 mg/m2) by oral, IV, or IA route of administration (n = 8 per group) and rats were followed for survival. Results: The ratio of drug delivery in tumor compared to normal left hemisphere was equivalent for the oral (2.51 ± 25) and IV (2.56 ± 0.87) routes (P = 0.90). After IA/BBBD, the tumor to brain ratio was 4.11 ± 1.12 and tumor-specific 14C-radioactivity was 85.4 ± 29.9 nCi/gram tissue, compared to 38.1 ± 19.9 nCi/gram tissue after IV administration (P = 0.019 by Student t-test). Median survival in untreated control rats was 17.5 days. A single temozolomide dose was effective at increasing survival when given by oral (median survival 25.5 days), IV (25.5 days), or IA (33 days) route of administration (overall P<0.0001 by the Log Rank test). Survival times in the oral and IV groups were significantly longer than control (P<0.001) but did not differ from each other, while survival time in the IA group was significantly longer than all other groups (P<0.01 for all comparisons). Temozolomide could not be given with BBBD in the efficacy study due to toxicities likely related to the diluent; there was no evidence of neurotoxicity in rats given IA temozolomide. Conclusions: Infusion of temozolomide into the internal carotid artery improved drug delivery and safely increased efficacy in a rat intracerebral tumor model. The improved efficacy suggests that a clinical trial of IA temozolomide is warranted in refractory glioblastoma. Citation Format: Leslie L. Muldoon, Michael A. Pagel, Edward A. Neuwelt. Safety and efficacy of intracarotid administration of temozolomide in a rat model of intracerebral metastasis. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4477. doi:10.1158/1538-7445.AM2013-4477

Study on chitosan-modified tripterygium glycoside nanoparticles and its renal targeting property

To prepare chitosan-modified tripterygium glycoside nanoparticles (LMWC-TG-PLA-NPs), and assess its renal targeting property in rats. Chitosan-modified tripterygium glycoside nanoparticles (LMWC-TG-PLA-NPs) were prepared by modified spontaneous emulsification solvent evaporation method, and modified with 50% deacetylated low molecular weight chitosan (LMWC). The shape of nanoparticles was observed under a transmission electron microscope. The mean diameter of nanoparticles was measured by particle size analyzer. The drug encapsulation efficiency and drug loading were measured by centrifuge method. The in vitro release behavior was studied with dialysis bags. Renal microdialysis technique and renal artery administration technique were combined to study the renal targeting property of nanopartcles. LMWC-TG-PLA-NPs were administrated in rats by tail vein injection (TVI) and renal artery administration (RAA), respectively, with TG-PLA-NPs as the control group. Renal dialysis fluid was regularly collected to determine the drug concentration in the dialysis fluid, map drug concentration-time curves, and calculate AUC ratio in kidneys through the two injection approaches as the renal targeting parameter (RTP), in order to assess the renal targeting property of LMWC-TG-PLA-NPs. The prepared LMWC-TG-PLA-NPs looked smooth and round. Their average diameter, polydispersity index, encapsulation efficiency and drug loading were (207.6 +/- 3.4) nm, (0.078 +/- 0.009)%, (61.83 +/- 2.43)%, and (10.70 +/- 0.37)%, respectively. The pH 7.4 PBS buffer solution containing 20% ethanol showed obvious sustained release behavior. LMWC-TG-PLA-NPs showed a RTP of 71.97%, which was 3.6 times of TG-PLA-NPs of the control group. The prepared LMWC-TG-PLA-NPs showed high drug encapsulation efficiency and drug loading, with obvious sustained release characteristics and renal targeting property. LMWC-TG-PLA-NPs are expected to become a new type vector for reducing toxic and side effects of tripterygium glycoside. Meanwhile, a new method is established for assessing renal targeting property with AUC ratio in kidneys after administrated through caudal veins and renal arteries as the renal targeting parameter.

Prostatic penetration of meropenem in humans, and dosage considerations for prostatitis based on a site-specific pharmacokinetic/pharmacodynamic evaluation

The aims of this study were to investigate the penetration of meropenem (MER) into human prostate tissue and to assess MER regimens for prostatitis by performing a site-specific pharmacokinetic/pharmacodynamic evaluation. Patients with prostatic hypertrophy (n=49) prophylactically received a 0.5-h infusion of MER (250mg or 500mg) before transurethral resection of the prostate. MER concentrations in plasma (0.5–5h) and prostate tissue (0.5–1.5h) were measured chromatographically. Concentration data were analysed pharmacokinetically with a three-compartment model and were used to estimate the drug exposure time above the minimum inhibitory concentration for bacteria (T>MIC, % of 24h) in prostate tissue, an indicator for antibacterial effects at the site of action. The prostate tissue/plasma ratio was 16.6% for the maximum drug concentration and 17.7% for the area under the drug concentration–time curve, irrespective of the dose. Against MIC distributions for clinical isolates of Escherichia coli, Klebsiella spp. and Proteus spp., 500mg once daily achieved a >90% probability of attaining the bacteriostatic target (20% T>MIC) in prostate tissue, and 500mg twice daily achieved a >90% probability of attaining the bactericidal target (40% T>MIC) in prostate tissue. However, against the Pseudomonas aeruginosa isolates, none of the tested regimens achieved a >90% probability of attaining the bacteriostatic or bactericidal targets.

Designs of Optimized Microbial Therapy Systems of Respiratory Infections

Several respiratory infections are frequently induced by pathogenic microorganisms in lung epithelial lining fluid (ELF) and alveolar macrophages (AM). Then, two studies concerning designs of antimicrobial therapy systems of respiratory infections were carried out; one was the distribution mechanisms of three macrolide and ketolide antibiotics, clarithromycin (CAM), azithromycin (AZM) and telithromycin (TEL) in plasma, ELF and AM, and the other was the efficient drug delivery to AM by pulmonary administration of fluoroquinolone antibiotic, a ciprofloxacin (CPFX) incorporated into liposomes (CPFX-liposome). In the first study, the areas under drug concentration-time curves (AUCs) in ELF following oral administration of three macrolide and ketolide antibiotics to rats were significantly higher than AUCs in plasma, furthermore AUCs in AM significantly higher than AUCs in ELF. The high distribution of these antibiotics to the respiratory infection site is due to the transport from blood to ELF via MDR1 in lung epithelial cells as well as the uptake by AM. These antibiotics were taken up by AM via active transport system and the trapping in organelles. In the second study, drug delivery efficacy of CPFX-liposome to AM was particle size-dependent over the 100-1000 nm and then become constant at over 1000 nm by pulmonary aerosolization to rats. This result indicates that the most effective size is 1000 nm. Furthermore, the drug delivery efficacy of mannosylated CPFX-liposome (particle size: 1000 nm) was highly delivered to AM and antibacterial effects were significantly higher than those of unmodified CPFX-liposome. This review provides useful findings for microbial therapy systems of respiratory infections.

Nanoemulsion improves the oral bioavailability of baicalin in rats: in vitro and in vivo evaluation

Baicalin is one of the main bioactive flavone glucuronides derived as a medicinal herb from the dried roots of Scutellaria baicalensis Georgi, and it is widely used for the treatment of fever, inflammation, and other conditions. Due to baicalin’s poor solubility in water, its absolute bioavailability after oral administration is only 2.2%. The objective of this study was to develop a novel baicalin-loaded nanoemulsion to improve the oral bioavailability of baicalin. Based on the result of pseudoternary phase diagram, the nanoemulsion formulation consisting of soy-lecithin, tween-80, polyethylene glycol 400, isopropyl myristate, and water (1:2:1.5:3.75:8.25, w/w) was selected for further study. Baicalin-loaded nanoemulsions (BAN-1 and BAN-2) were prepared by internal or external drug addition and in vivo and in vitro evaluations were performed. The results showed that the mean droplet size, polydispersity index, and drug content of BAN-1 and BAN-2 were 91.2 ± 2.36 nm and 89.7 ± 3.05 nm, 0.313 ± 0.002 and 0.265 ± 0.001, and 98.56% ± 0.79% and 99.40% ± 0.51%, respectively. Transmission electron microscopy revealed spherical globules and confirmed droplet size analysis. After dilution 30-fold with water, the solubilization capacity of BAN-1 and BAN-2 did not change. In vitro release results showed sustained-release characteristics. BAN-1 formulation was stable for at least 6 months and was more stable than BAN-2. In rats, the area under the plasma drug concentration-time curve value of BAN-1 was 1.8-fold and 7-fold greater than those of BAN-2 and free baicalin suspension after oral administration at a dose of 100 mg/kg. In conclusion, these results demonstrated that the baicalin-loaded nanoemulsion formulation, in particular BAN-1, was very effective for improving the oral bioavailability of baicalin and exhibited great potential for future clinical application.

Population pharmacokinetic analysis of fluconazole to predict therapeutic outcome in burn patients with Candida infection.

The pharmacokinetic (PK) property of fluconazole might be significantly altered in major burn patients by medical interventions and physiologic changes. In this study, our aims were to investigate fluconazole PK in burn patients using a population approach and to recommend the optimal fluconazole regimen based upon the predicted therapeutic outcome. At steady state, blood samples for PK analysis were obtained from 60 burn patients receiving between 100 and ~400 mg fluconazole daily. A mixed-effect modeling was performed and the therapeutic outcome of antifungal therapy was predicted for 10,000 virtual patients using NONMEM (version 7.2). MIC values were sampled from the MIC distribution at the study site. An area under the free drug concentration-time curve (fAUC)/MIC measurement of >25 h was used as the criterion for therapeutic success. When the same dose was given, the plasma concentration of fluconazole was predicted to be lower in burn patients compared to the nonburn population because of the large PK parameter (clearance, volume of distribution) estimates and continuous renal replacement therapy (CRRT). This tendency was particularly predominant when the patients were within 30 postburn days. Based upon our findings, 400 mg/day fluconazole is recommended to obtain therapeutic successes in major burn patients.

Penetration of meropenem into human pancreatic juice

This study examined the penetration of meropenem into pancreatic juice in patients who had undergone hepato-biliary-pancreatic surgery. The patients received a 0.5-h infusion of 500 mg meropenem. The observed maximum concentration (mean ± standard deviation, n = 5) was 39.1 ± 11.2 μg/ml at 0.5 h in plasma and 2.12 ± 0.73 μg/ml at 1.10 ± 0.14 h in pancreatic juice. The pancreatic juice/plasma ratio was 0.06 ± 0.02. The area under the drug concentration-time curve was 73.0 ± 37.5 μg•h/ml in plasma and 4.24 ± 2.77 μg•h/ml in pancreatic juice. The pancreatic juice/plasma ratio was 0.06 ± 0.01. The mean drug-exposure times above 0.125 μg/ml and 0.25 μg/ml (the minimum inhibitory concentrations (MIC) for common pathogens) in pancreatic juice were 99.4% and 87.3%, respectively, for 500 mg meropenem 3 times daily. This commonly used regimen for pancreatitis achieved the drug-exposure time target (40% of the time above the MIC) at the action site, despite the low penetrability of meropenem.

Integrated Pharmacokinetic-Driven Approach to Screen Candidate Anticancer Drugs for Brain Tumor Chemotherapy

The goal of the study was to develop an effective screening strategy to select new agents for brain tumor chemotherapy from a series of low molecular weight anticancer agents [ON123x] by the combined use of in silico, in vitro cytotoxicity, and in vitro ADME profiling studies. The results of these studies were cast into a pipeline of tier 1 and tier 2 procedures that resulted in the identification of ON123300 as the lead compound. Of the 154 ON123xx compounds, 13 met tier 1 screening criteria based on physicochemical properties [i.e., MW < 450 Da, predicted log P between 2 and 3.5] and in vitro glioma cell cytotoxicity [i.e., IC50 < 10 μM] and were further tested in tier 2 assays. The tier 2 profiling studies consisted of metabolic stability, MDCK-MDR1 cell permeability and plasma and brain protein binding that were combined to globally assess whether favorable pharmacokinetic properties and brain penetration could be achieved in vivo. In vivo cassette dosing studies were conducted in mice for 12 compounds that permitted examination of in vitro/in vivo relationships that confirmed the suitability of the in vitro assays. A parameter derived from the in vitro assays accurately predicted the extent of drug accumulation in the brain based on the area under the drug concentration-time curve in brain measured in the cassette dosing study (r (2) = 0.920). Overall, the current studies demonstrated the value of an integrated pharmacokinetic-driven approach to identify potentially efficacious agents for brain tumor chemotherapy.

Fabrication and evaluation of pH-modulated solid dispersion for telmisartan by spray-drying technique

The present study was undertaken to overcome the problems associated with solubility, dissolution and oral bioavailability of a poorly water-soluble ionizable drug, telmisartan (TMS). For these purposes, a solubility test was carried to select the appropriate formulation composition from various carriers and alkalizers. Solid dispersions (SDs) of TMS were prepared at different drug-to-carrier ratios by the spray-drying technique, and were characterized by dissolution and aqueous solubility studies. The optimum formulation was investigated by dissolution studies at different pH and water media and its solid state characterisations were performed by scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and X-ray diffraction (XRD) studies. In solubility and dissolution tests, all TMS-loaded pH-modulated SDs (pH(M)-SDs) exhibited marked improvement in the dissolution behavior when compared with crystalline TMS powder. The optimum formulation of pH(M)-SD consisted of TMS/PVP (polyvinylpyrrolidone) K30/Na(2)CO(3) at a weight ratio of 2/0.5/3 and showed significant improvement in the aqueous solubility and dissolution rate by approximately 40,000- and 3-fold, respectively, compared to TMS powder. Solid-state characterization revealed the changed in crystallinity of TMS into amorphous state. Furthermore, area under the drug concentration time-curve (AUC) of TMS from the pH(M)-SD increased by 13.4- and 2.1-fold, compared with TMS powder and commercial product, respectively. According to these observations, taken together with dissolution and pharmacokinetic behaviors, pH-modulated SD in the presence of an alkalizer for a poorly water-soluble ionizable drug, TMS, appeared to be efficacious for enhancing its bioavailability.

Use of Partial AUC (PAUC) to Evaluate Bioequivalence—A Case Study with Complex Absorption: Methylphenidate

Methylphenidate modified-release products produce early and late peak concentrations critical for treatment of morning and afternoon symptoms of attention deficit hyperactivity disorder (ADHD). Standard bioequivalence (BE) criteria cannot be applied to these products. The performance of partial area under the drug concentration-time curve (PAUC), Cmax and AUCINF to assess BE were independently evaluated for two products. A two-stage analysis was performed on plasma data for two methylphenidate modified-release products (Product 1 and 2). Simulations using the fitted parameters determined how changes in fast absorption rate constant (K0Fast) and fraction available (F1) affected curve shape and BE determination using Cmax, AUCINF and PAUC. The sensitivity of the mean PAUC(test)/PAUC(reference) ratios to changes in K0Fast(test) are product dependent. Product 1 mean PAUC(test)/PAUC(reference) ratios for PAUC0-4h are more responsive to both decreases and increases in K0Fast(test) than Product 2. Product 2 showed a greater response in the mean PAUC(test)/PAUC(reference) ratio for PAUC0-4h when the K0Fast(test) is decreased and less response as the value is increased. PAUC estimated curve shape is sensitive to changes in absorption and are product specific, and may require a new PAUC metric for each drug. A non-product specific metric to assess curve shape is warranted.

Development of ligustrazine-loaded lipid emulsion: Formulation optimization, characterization and biodistribution

Ligustrazine is a traditional Chinese medicine used to treat various cardiovascular and neurovascular complications. However, this compound exhibits rapid first-pass metabolism, a short biological half-life, low stability and potential vascular irritation that restrict its use for long-term therapy. The use of a lipid emulsion as a carrier for intravenous administration of ligustrazine might provide sustained and prolonged release, thereby reducing the frequency of administration and improving patient compliance. The main purpose of our study was to develop a highly stable and sterile optimal formulation of a ligustrazine lipid emulsion (LLE) and to evaluate its pharmacokinetic behavior and tissue distribution in rats. The final optimal formulation consisted of soybean oil (12.0%), oleic acid (0.6%), lecithin (1.0%), poloxamer 188 (0.6%) and glycerol (2.25%). The average particle size, polydispersity index (PDI), zeta-potential and pH of the final product were 215.0±2.5 nm, 0.076±0.033, -40.4±5.3 mV and 7.25±0.05, respectively. The LLE was stable for at least three months at room temperature. In vitro drug release studies of the LLE suggested a sustained release profile, which was further confirmed by in vivo pharmacokinetic studies in rats. The area under the drug concentration-time curve from 0 h to 10 h (AUC(0-10h)) for LLE was increased by 1.6-fold compared with that of the commercially available ligustrazine injection (LI), suggesting enhanced bioavailability from the lipid-based emulsion. Furthermore, a tissue distribution study showed significant improvement in the distribution pattern of ligustrazine with a higher AUC(0-180 min) observed in all tissues for LLE than for LI. In conclusion, LLE, with excellent stability, improved pharmacokinetics and tissue distribution, demonstrates great potential for the delivery of ligustrazine for clinical applications.

Testing the mutant selection window in rabbits infected with methicillin-resistant Staphylococcus aureus exposed to vancomycin

To test the mutant selection window (MSW) hypothesis with Staphylococcus aureus exposed to vancomycin in an animal model and to compare in vivo and in vitro exposures that restrict the enrichment of resistant mutants. Local infection with S. aureus was established in rabbits, and the infected animals were treated with various doses of twice-daily vancomycin (half-life 6 h) for 3 consecutive days to provide antibiotic concentrations below the MIC, between the MIC and the mutant prevention concentration (MPC), and above the MPC. Changes in susceptibility and the numbers of surviving organisms were monitored daily on agar plates containing 2× and 4× MIC of vancomycin. S. aureus lost vancomycin susceptibility when drug concentrations at the site of infection fluctuated between the lower and upper boundaries of the MSW, defined in vitro as the MIC(99) and the MPC, respectively. Both boundaries were determined in vitro, before starting animal studies. The value at which resistant mutants are not enriched in vivo was estimated as an AUC(24)/MPC value of ∼15 h, where AUC(24) is the area under the drug concentration time curve in a 24 h interval. The estimated anti-mutant AUC/MIC ratio in vivo was ≥200 h. These findings support the MSW hypothesis and the anti-mutant AUC/MIC ratio estimated in vivo is consistent with that reported in in vitro studies. Keeping vancomycin concentrations above the MPC or AUC(24)/MPC >15 h is a straightforward way to restrict the acquisition of resistance.

Comparison on in vivo pharmacokinetics of brucine, total alkaloids of Strychni Semen and Strychni Semen pulveratum in rats

To study different in vivo pharmacokinetic regularity of brucine, total alkaloids of scorched sand-prepared Strychni Semen products and Strychni Semen pulveratum in rats, and probe into mutual impact between single component and compound. Rats in each group were orally administered with brucine, total alkaloids of scorched sand-prepared Strychni Semen products and Strychni Semen pulveratum suspension. The in vivo plasma concentrations of brucine in rats were determined by HPLC. A compartment model was made for the blood drug concentration-time curve using 3P97 software package and the pharmacokinetic parameters of each group were calculated and compared. The in vivo metabolic process of brucine in rats complied with the two-compartment model, weight W = 1/C2. The results of variance analysis showed that among three existing forms of brucine with same dosage, the brucine solution group and the total alkaloids group of scorched sand-prepared Strychni Semen products showed significant differences in C(max), MRT (P < 0.05); and the brucine solution group and the Strychni Semen pulveratum suspension group showed significant differences in C(max), AUC(0-t), and AUC(0-infinity), in which the latter displayed minimum C(max), AUC(0-t) and AUC(0-infinity). The total alkaloids group of scorched sand-prepared Strychni Semen products showed a relatively longer retention time of effective components of brucine in plasma, while the Strychni Semen pulveratum suspension group showed a lower bioavailability.

Enhanced bioavailability and cysticidal effect of three mebendazole-oil preparations in mice infected with secondary cysts of Echinococcus granulosus

The aim of the present study is to explore the possibility to increase the efficacy of mebendazole (MBZ) against secondary cysts of Echinococcus granulosus harbored in mice by augmenting the solubility and bioavailability of the drug. Firstly, the saturated solubility of MBZ in nine kinds of oil was determined by high performance liquid chromatography (HPLC), and MBZ was found exhibiting the highest, secondary, and lowest solubility in oleic acid (OA), glycerol trioleate (GT), and soybean oil (SB), respectively. Secondly, MBZ-OA suspension, MBZ-GT suspension, MBZ-SB suspension, and MBZ suspended in 1 % tragacanth (MBZ-1 % tragacanth) were selected for further studies on pharmacokinetics and experimental therapy in mice. Four groups of mice were treated orally with one of aforementioned four MBZ preparations at a single dose of 25 mg/kg, and concentrations of MBZ in plasma obtained from each mouse at various intervals within 24 h postadministration were determined by HPLC. The major pharmacokinetic parameters calculated by MBZ plasma concentration-time curve demonstrated that the peak concentration of the drug (C (max) ) values obtained from three MBZ-oil preparation groups was 1.6-2.8 times higher than that of MBZ-1 % tragacanth group. The same was true that the area under the drug concentration-time curve (AUC(0-∞)) values of 19.8 (2.5)-28.2 (2.5) μg/ml × h revealed in the three MBZ-oil preparation groups was significantly higher than that of 11.6 (2.0) μg/ml × h in MBZ-1 % tragacanth group, and the bioavailability of the three MBZ-oil preparation groups was 71-143 % higher than that of MBZ-1 % tragacanth group. In mice infected with secondary cysts of E. granulosus for 8 months treated orally with MBZ-1 % tragacanth at a daily dose of 25 mg/kg for 14 consecutive days, the mean cyst weight was lower than that of untreated control, but the difference was not statistically significant with cyst weight reduction of 48 %. When the infected mice received three MBZ-oil preparations at the same oral dose schedule as aforementioned, the mean cyst weights were significantly lower than those in MBZ-1 % tragacanth group or control group with cyst weight reductions of 71.2-84.7 %. The results indicate that the solubility of MBZ in oils may increase to various degrees according to the kinds of oil used. Meanwhile, three MBZ-oil (OA, GT, and SB) preparations administered orally to mice not only improve the bioavailability of MBZ relative to that of MBZ suspended in 1 % tragacanth, but their effects against hydatid cysts also significantly enhance.

Development of novel ibuprofen-loaded solid dispersion with enhanced bioavailability using cycloamylose

To develop a novel ibuprofen-loaded solid dispersion with enhanced bioavailability using cycloamylose, it was prepared using spray-drying techniques with cycloamylose at a weight ratio of 1:1. The effect of cycloamylose on aqueous solubility of ibuprofen was investigated. The physicochemical properties of solid dispersions were investigated using scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and X-ray diffraction. The dissolution and bioavailability in rats were evaluated compared with ibuprofen powder. This ibuprofen-loaded solid dispersion improved about 14-fold drug solubility. Ibuprofen was present in an unchanged crystalline state, and cycloamylose played the simple role of a solubilizing agent in this solid dispersion. Moreover, the dispersion gave 2-fold higher AUC (area under the drug concentration-time curve) value compared with a ibuprofen powder, indicating that it improved the oral bioavailability of ibuprofen in rats. Thus, the solid dispersion may be useful to deliver ibuprofen with enhanced bioavailability without crystalline change.

Role of a novel pyridostigmine bromide-phospholipid nanocomplex in improving oral bioavailability

A novel pyridostigmine bromide (PB)-phospholipid nanocomplex (PBPLC) was prepared to increase the bioavailability of PB. A central composite design approach was employed for process optimization. The physicochemical properties of PBPLC were investigated by means of differential scanning calorimetry, ultraviolet spectroscopy, Fourier transformed infrared spectroscopy and the n-octano/water partition coefficient. The intestinal permeability of PBPLC was observed via a single pass intestinal perfusion in rats. After oral administration of PBPLC, the concentrations of PB at predetermined time points were determined by HPLC, and the pharmacokinetic parameters were computed by DAS 2.1.1 software. Multiple linear regression analysis for process optimization revealed that the optimal PBPLC was obtained when the values of X(1), X(2), and X(3) were 8, 40°C, and 4 mg/mL, respectively. The average particle size and zeta potential of PBPLC with the optimized formulation were 204.60 nm and -25.12 mV, respectively. Non-covalent interactions between PB and phospholipids were found in the PBPLC. The n-octanol/water partition coefficient of PBPLC was substantially increased. PBPLC had better intestinal permeability in comparison with free PB. Mean plasma drug concentration-time curves of PBPLC and free PB after oral administration were both in accordance with the two-compartment open model. The values of pharmacokinetic parameters of PBPLC and free PB were the peak time (T(max)) 2 h vs 2 h, the maximum concentration (C(max)) 22.79 μg/mL vs 6.00 μg/mL, and the value of the area under the concentration vs time curve (AUC(0-∞)) 7128.21 μg·min/mL vs 1772.36 μg·min/mL, respectively. In conclusion, compared with free PB, PBPLC remarkably improves the oral bioavailability of PB, which is likely due to its higher lipophilicity and permeability.

Determination of doripenem penetration into human prostate tissue and assessment of dosing regimens for prostatitis based on site-specific pharmacokinetic–pharmacodynamic evaluation

Prostatic hypertrophy patients prophylactically received a 0·5-hour infusion of doripenem (250 or 500 mg) before transurethral resection of the prostate. Doripenem concentrations in plasma and prostate tissue were measured chromatographically, and analysed pharmacokinetically using a three-compartment model. The approved doripenem regimens were assessed based on the time above the minimum inhibitory concentration for bacteria (T>MIC, % of 24 hours), an indicator for antibacterial effects, at the prostate. The prostate tissue/plasma ratios were 17·3% for the maximum drug concentration and 18·7% for the area under the drug concentration–time curve, and they were irrespective of the dose. Against Escherichia coli and Klebsiella species isolates, 500 mg once daily achieved a >90% probability of attaining the bacteriostatic target (20% T>MIC) in prostate tissue, and 500 mg twice daily achieved a >90% probability of attaining the bactericidal target (40% T>MIC) in prostate tissue.

Enhancement of the dissolution rate and bioavailability of fenofibrate by a melt-adsorption method using supercritical carbon dioxide

Background:The aim of this study was to enhance the bioavailability of fenofibrate, a poorly water-soluble drug, using a melt-adsorption method with supercritical CO2.Methods:Fenofibrate was loaded onto Neusilin® UFL2 at different weight ratios of fenofibrate to Neusilin UFL2 by melt-adsorption using supercritical CO2. For comparison, fenofibrate-loaded Neusilin UFL2 was prepared by solvent evaporation and hot melt-adsorption methods. The fenofibrate formulations prepared were characterized by differential scanning calorimetry, powder x-ray diffractometry, specific surface area, pore size distribution, scanning electron microscopy, and energy-dispersive x-ray spectrometry. In vitro dissolution and in vivo bioavailability were also investigated.Results:Fenofibrate was distributed into the pores of Neusilin UFL2 and showed reduced crystal formation following adsorption. Supercritical CO2 facilitated the introduction of fenofibrate into the pores of Neusilin UFL2. Compared with raw fenofibrate, fenofibrate from the prepared powders showed a significantly increased dissolution rate and better bioavailability. In particular, the area under the drug concentration-time curve and maximal serum concentration of the powders prepared using supercritical CO2 were 4.62-fold and 4.52-fold greater than the corresponding values for raw fenofibrate.Conclusion:The results of this study highlight the usefulness of the melt-adsorption method using supercritical CO2 for improving the bioavailability of fenofibrate.

Development and Validation of Limited Sampling Strategies for Estimation of Cyclosporine Area Under the Concentration–Time Curve in Hematopoietic Stem Cell Transplant Patients

The aim of this study was to develop and validate limited sampling strategies for accurately predicting 12-hour area under the concentration-time curve (AUC(0-12 h)) to provide a practical method for more precise therapeutic drug monitoring of cyclosporine A in stem cell transplant patients. Steady-state cyclosporine blood concentrations were measured within a dosing interval (12 hours post administration) in 35 allogeneic bone marrow transplant patients receiving 238 mg (±117 mg) twice-daily dose of cyclosporine. Limited sampling strategies were developed by multiple linear regression analysis of relationship between cyclosporine A full AUC(0-12 h) values and different combinations of preselected blood concentrations. Validation of the estimating equations was done by a bootstrap-like cross-validation method. Cross-validation results showed that cyclosporine AUC(0-12 h) could be estimated using either 2 or 3 samples within the first 4 hours after drug administration with good accuracy and precision (absolute prediction error of less than 6.2%). The number of estimated area under the drug concentration-time curves within 15% of observed values was greater than 26 (74%) for models used predose concentration with either c(2h) and c(4h) or both. Most of the previously reported single-sample models showed a systematic error in predicting AUC(0-12 h). Although a statistically significant difference in precision of prediction was seen between 3-sample model using c(0), c(2h), and c(4h) and 2-sample models (c(0), c(2h) or c(0), and c(4h)), such a difference (2%) could not be of clinical importance. Other 2-sample estimating equations (models using c(2h) with either c(6h) or c(10h)) with the same degree of precision appear to be less feasible clinically. Cyclosporine AUC(0-12 h) in bone marrow transplant patients could be estimated using 2 or 3 samples within the first 4 hours after drug administration with good accuracy and precision.

Tacrolimus Pharmacokinetics in Hispanic Children After Kidney Transplantation

Ethnic differences in drug pharmacokinetics are well recognized including that for tacrolimus (TAC) in adult subjects. However, similar knowledge among pediatric populations is missing. Our limited retrospective study compares steady-state pharmacokinetics of TAC in Hispanic versus non-Hispanic children. Serial blood samples were collected and whole blood concentrations of TAC were measured using radioimmunoassay. Compared with non-Hispanic children, Hispanic children had lower measures of drug exposure (maximum drug concentration [C max] and area under the drug concentration-time curve [AUC 0-∞]), higher volume of distribution, and faster clearance. Interestingly, only in Hispanic children, significant correlations were found between body weight and clearance, age and volume of distribution, and Schwartz estimated glomerular filtration rate and half-life. In conclusion, our study suggests that ethnic differences exist between Hispanic and non-Hispanic children in TAC PK, and based on our preliminary findings, either a higher or more frequent TAC dosing may be required for effective immunosuppression therapy in Hispanic children.