Compatibility of Commonly Used Active Pharmaceutical Ingredients in a Ready-to-Use Oral Suspending Vehicle.

The present study aimed to evaluate the stability of active pharmaceutical ingredients (APIs) from different pharmacological classes in a compounded oral suspending vehicle. Oral suspensions of amoxicillin trihydrate (50 mg/mL), clozapine (25 mg/mL), indomethacin (5.0 mg/mL), levodopa/carbidopa (10.0/2.5 mg/mL), levothyroxine sodium (T4, 25 µg/mL), lomustine (4.0 and 10.0 mg/mL), methyldopa (25 mg/mL) and procarbazine (10.0 mg/mL) were formulated in SyrSpend® SF PH4 and the stability was monitored for up to 90 days, except for amoxicillin trihydrate, which was evaluated for 30 days only. The APIs' stability was determined by measuring percent recovery using stability-indicating high-performance liquid chromatography (HPLC or UHPLC) or titration (amoxicillin trihydrate only). The stability of amoxicillin trihydrate, clozapine, indomethacin and levodopa/carbidopa were studied at both refrigerated (2-8 °C) and room temperature (20-25 °C). Lomustine, procarbazine, and methyldopa were studied at refrigerated temperature only. Our data demonstrated promising stability for the compounded suspensions containing various APIs, investigated in SyrSpend® SF PH4, as all APIs exhibited stability throughout the study duration and met content uniformity criteria. These findings lead to the conclusion that the tested compounded oral suspensions present a viable approach for creating personalized, age-appropriate formulations. The capacity to ensure dose consistency and stability using APIs from diverse pharmacological classes renders them suitable choices for both pediatric and geriatric patients.

Compatibility of Gestrinone, Nimesulide, and Piroxicam in Pentravan for Transdermal and Transmucosal Application.

Transdermal products are intended to be applied topically but to promote the biological effects systemically, while transmucosal products have the same final effect but are to be applied on mucosa (for example, vaginal mucosa). The extension and velocity in which absorption occurs vary depending on the vehicle used, the active pharmaceutical ingredient and a broad range of other factors related to the formulation, patient, and environmental characteristics. Ready-to-use vehicles, such as Pentravan, with proven penetration efficacy for various active pharmaceutical ingredients, are paramount. Pentravan, specially developed for compounding pharmacies, has been extensively studied. To date, most studies have focused on endocrinology (e.g., sexual hormones), anti-aging strategies, and gynecology (endometriosis and related conditions). In this work, we have determined the compatibility of Pentravan and three active pharmaceutical ingredients: gestrinone, a steroidal substance for vaginal use (endometriosis), and nimesulide and piroxicam, two nonsteroidal anti-inflammatory drugs used both for topical and vaginal application. This article shows an excellent beyond-use date of 180 days when stored at room temperature, which renders it suitable for daily practice.

Compatibility of Estradiol, Estriol, Estrone, Progesterone, and Testosterone Single Formulation in Fitalite, Versatile, or HRT Supreme Cream Base.

In this work, we focus on three ready-to-use vehicles: Fitalite, Versatile, and HRT Supreme Cream Base. Fitalite is a natural, light, hydrophilic gel-cream that contains vitamin E and oil bodies from plant sources (phytosomes), providing antioxidant and skinmoisturizing properties. Versatile is a vanishing oil-inwater cream base which retains its consistency with a broad range and high concentrations of active pharmaceutical ingredients, dermaceutical ingredients, and solvents. Finally, HRT Supreme Cream Base is a paraben-free, dye-free, fragrance-free O/W emulsion base, formulated with a complex of botanical oils to soothe and provide moisture to dry and sensitive skin. In the current study, we evaluated the beyond-use date of formulations containing estradiol, estriol, estrone, progesterone, and testosterone in combination, compounded with these three vehicles. Validated, stability-indicating high-performance liquid chromatography methods were used throughout a 180-day period. A beyond-use date of 180 days was observed for all vehicles stored both at refrigerated and at room temperature. The combination of five ingredients represents a worst-case scenario since there are more possibilities of cross reactions. Therefore, we expect the same or greater stability as individual ingredients are removed from the tested formulation. The extended beyond-use dates provide convenience for both the compounding pharmacist and the patient.

Characterization and Safety Profile of Transfer Factors Peptides, a Nutritional Supplement for Immune System Regulation.

Imuno TF® is a nutritional supplement composed of isolated transfer factors (TF) from porcine spleen. It is composed of a specific mixture of molecules that impact functions of the biological systems and historically is linked to the immune system regulation. In this study, we demonstrate for the first time its proteomic analysis, nutritional composition, and safety profile in terms of mutagenic potential and acute oral dose (LD50). The obtained analysis indicated the product is a complex set of oligo- and polypeptides constituted of 163 different peptides which can potentially act on multiple mechanisms on the immune system pathways. The chemical composition showed low fat and low sugar content, saturated fatty acids-free, and the presence of 10 vitamins and 11 minerals. No mutagenic effect was observed, and the LD50 was 5000 mg kg-1 body weight. This accounts for a safe product to be used by the oral route, with potential benefits for the immune system.

Always the Right Dose? Content Uniformity in Over 100 Different Formulations Tested.

There is still an evident need for nonsterile compounded medications for pediatric and elderly patients in cases where patients require dose adjustments or have swallowing difficulties. Pharmacists generally have the choice between compounding capsules or oral liquids. In daily pharmacy practice, extemporaneous capsules are from time to time seen as a better alternative to oral liquid medication, although various published studies indicate that weight variation and/or uniformity of content can be significantly out of specification for compounded capsules. In contrast, analyses with the ready-to-use oral liquid vehicle SyrSpend SF in 104 different formulations with 89 unique active pharmaceutical ingredients showed results that all 6.414 samples analyzed were within specification. It can, therefore, be argued that SyrSpend SF could be a better way to assure content uniformity compared to manually compounded, small-batch extemporaneous capsules.

Efficacy of an Automated Robotic Cleaning Device for Compounding Pharmacies.

Compounded medicinal products should be prepared using an appropriate quality-assurance system. Cleaning and disinfection, as part of this system, are important to avoid cross-contamination of the preparations, reduce the bioburden levels in products, and avoid hazardous drugs residues or toxic chemical exposure of the staff workers. However, manual cleaning is difficult to standardize. Automated robotic cleaning devices are currently available and designed for domestic use only. To fill this gap, a laboratory automated robotic cleaning device (RVC1, FagronLab, The Netherlands) was specially developed to clean and sanitize laboratories of compounding pharmacies and other production facilities of primary healthcare establishments. The objective of this study was to evaluate the efficacy of an automated robotic cleaning device (robotic vacuum cleaner) for compounding pharmacies and other production facilities of primary healthcare establishments. A set of 6 experiments was conducted to evaluate the efficacy of the cleaning procedure using the automated robotic cleaning device. All experiments were conducted at the end of a regular daily routine in the laboratory to simulate a genuine cleaning procedure. Tests were performed both with no forced contamination (to imitate the regular use of the device) and with forced contamination (to mimic unexpected, non-regular contamination, such as in the case of accidents). Total aerobic microbial count and the total combined yeasts and molds count were determined, as well as pathogens identification and the concentration of thiamine hydrochloride and progesterone active pharmaceutical ingredients (deliberately spread on the floor surface for the tests). In real-conditions, both two-step and single-step were adequate to clean the areas and reduce microbiological contamination to non-detected levels, and only the cleaning cycle without the mopping accessory was also suitable (in the two-step cleaning). The same can be seen for the forced-contamination condition, except for the use of the cleaning cycle without the mopping. In terms of chemical contamination, both high and low water-soluble active pharmaceutical ingredients were reduced (completely and 932-fold, respectively) in the single-step cleaning. The RVC1 automated robotic cleaning device showed the necessary microbiological and chemical efficacy to be used in the cleaning routine of compounding pharmacies, both in a singlestep cleaning (brushing, ultraviolet light, and mopping simultaneously) or in a double-step cleaning (brushing and ultraviolet light first, mopping second). It is then recommended to always use the mopping accessory and the ultraviolet light on. The RVC1 can be a valuable add-on method to standardize cleaning.

Postulated Adjuvant Therapeutic Strategies for COVID-19.

The number of COVID-19 patients is still growing exponentially worldwide due to the high transmissibility of the SARS-CoV-2 virus. Therapeutic agents currently under investigation are antiviral drugs, vaccines, and other adjuvants that could relieve symptoms or improve the healing process. In this review, twelve therapeutic agents that could play a role in prophylaxis or improvement of the COVID-19-associated symptoms (as add-on substances) are discussed. Agents were identified based on their known pharmacologic mechanism of action in viral and/or nonviral fields and are postulated to interact with one or more of the seven known mechanisms associated with the SARS-CoV-2 virus: (i) regulation of the immune system; (ii) virus entrance in the cell; (iii) virus replication; (iv) hyperinflammation; (v) oxidative stress; (vi) thrombosis; and (vii) endotheliitis. Selected agents were immune transfer factor (oligo- and polypeptides from porcine spleen, ultrafiltered at <10 kDa; Imuno TF®), anti-inflammatory natural blend (Uncaria tomentosa, Endopleura uchi and Haematoccocus pluvialis; Miodesin®), zinc, selenium, ascorbic acid, cholecalciferol, ferulic acid, spirulina, N-acetylcysteine, glucosamine sulfate potassium hydrochloride, trans-resveratrol, and maltodextrin-stabilized orthosilicic acid (SiliciuMax®). This review gives the scientific background on the hypothesis that these therapeutic agents can act in synergy in the prevention and improvement of COVID-19-associated symptoms.

Stability of Azathioprine, Clonidine Hydrochloride, Clopidogrel Bisulfate, Ethambutol Hydrochloride, Griseofulvin, Hydralazine Hydrochloride, Nitrofurantoin, and Thioguanine Oral Suspensions Compounded with SyrSpend SF pH4.

To allow for tailored dosing and overcome swallowing difficulties, compounded liquid medication is often required in pediatric patients. The objective of this study was to evaluate the stability of oral suspensions compounded with SyrSpend SF PH4 and the commonly used active pharmaceutical ingredients azathioprine (powder) 50 mg/mL, azathioprine (from tablets) 50 mg/mL, clonidine hydrochloride (powder) 0.1 mg/mL, clopidogrel bisulfate (from tablets) 5 mg/mL, ethambutol hydrochloride (powder) 50 mg/mL, ethambutol hydrochloride (from tablets) 50 mg/mL, ethambutol hydrochloride (powder) 100 mg/mL, griseofulvin (powder) 25 mg/mL, hydralazine hydrochloride (powder) 4 mg/mL, nitrofurantoin (powder) 10 mg/mL, and thioguanine (powder) 2.5 mg/mL. Suspensions were compounded at the concentrations listed above and stored at controlled room and refrigerated temperatures. Stability was assessed by measuring the percentage recovery at 0 day (baseline), and at 7 days, 14 days, 30 days, 60 days, and 90 days. Active pharmaceutical ingredients quantification was performed by high-performance liquid chromatography, via a stability-indicating method. The following oral suspensions compounded using SyrSpend SF PH4 as the vehicle showed a beyond-use date of 90 days when stored both at room or refrigerated temperatures: clonidine hydrochloride 0.1 mg/mL, ethambutol hydrochloride 50 mg/mL and 100 mg/mL, griseofulvin 25 mg/mL, nitrofurantoin 10 mg/mL, and thioguanine 2.5 mg/mL, all compounded from the active pharmaceutical ingredients in powder form. Suspensions compounded using the active pharmaceutical ingredients from tablets presented a lower beyond-use date: 30 days for ethambutol hydrochloride 50 mg/mL and hydralazine hydrochloride 4 mg/mL, stored at both temperatures, and for clopidogrel bisulfate 5 mg/mL when stored only at refrigerated temperature. Azathioprine suspensions showed a beyond-use date of 14 days when compounded using active pharmaceutical ingredients in powder form at both temperatures. This suggests that SyrSpend SF PH4 is suitable for compounding active pharmaceutical ingredients from different pharmacological classes.

Comparison of Rheological and Sedimentation Behavior of Commercially Available Suspending Vehicles for Oral Pharmaceutical Preparations.

A pharmaceutical suspension is a semi-liquid dosage form suitable for patients being unable to swallow solid medicines such as tablets and capsules. A vehicle used for the preparation of pharmaceutical oral suspensions preferably shows pseudo-plastic behavior. In a product that gets thinner with agitation and thicker upon standing, slow settlement of the suspended active pharmaceutical ingredient is combined with good pourability and rehomogenization. This gives the best guarantee of uniformity of dose for oral suspensions. In this study, the rheological behavior of commercially available ready-to-use vehicles for oral pharmaceutical preparations was compared, and the sedimentation of paracetamol dispersed in these vehicles was investigated. With SuspendIt and SyrSpend SF PH4 (Liquid), both pseudoplastic vehicles, very stable paracetamol suspensions were obtained. Of these two vehicles, SyrSpend SF PH4 (Liquid) displayed somewhat higher viscosity, which is a favorable quality characteristic for suspensions.

Limited Influence of Excipients in Extemporaneous Compounded Suspensions.

Objective: The objective of this study was to identify whether compounding oral suspensions with SyrSpend SF based on tablets or capsules is a suitable alternative for using raw pharmaceutical materials. Methods: Suspensions based on 5 different tablets and capsules were studied in SyrSpend SF. The summary of product characteristics of these different tablets and capsules were obtained from the manufacturer. Our hypothesis was that, if the maximum beyond-use date of the study was reached, the excipient did not seem to have an influence on the stability of the active pharmaceutical ingredient (API) within the studied time frame. Results: All excipients used in flecainide acetate, labetalol HCl, and tiagabine HCl tablets as well as in celecoxib and oseltamivir capsules did not seem to influence the beyond-use date of the overall suspension based on SyrSpend SF. Conclusion: Although using raw materials as API sources is preferred, oral suspensions with SyrSpend SF prepared from crushed tablets or opened capsules could be a possible alternative. Based on this study, a wide range of different excipients does not seem to impact the beyond-use date of different APIs compounded in SyrSpend SF.

Suspensions as a Valuable Alternative to Extemporaneously Compounded Capsules.

The objective of this study was to determine the variation in content of 74 different active pharmaceutical ingredients (APIs) and compare it with what is known in the literature for the content uniformity of extemporaneous prepared capsules. Active pharmaceutical ingredients quantification was performed by high-performance liquid chromatography, via a stability-indicating method. Samples for all active pharmaceutical ingredients were taken throughout a 90-day period and the content was determined. In total, 5,190 different samples were analyzed for 74 different active pharmaceutical ingredients at room (15°C to 25°C) or controlled refrigerated temperature (2°C to 8°C). Each of these datasets was analyzed according to the United States Pharmacopeia Content Uniformity monograph, corrected for the sample number. The mean acceptance values were well within specifications. In addition, all suspensions complied with the criteria defined by the British Pharmacopoeia monograph for Content Uniformity of Liquid Dispersions for both room and controlled refrigerated temperature. In previous studies, it was found that a routine weight variation check is often not sufficient for quality assurance of extemporaneous prepared capsules. Compounded oral liquids show little variation in content for 74 different active pharmaceutical ingredients; therefore, compounded oral liquids are a suitable alternative when compounding individualized medications for patients.

Multidrug resistance in oncology and beyond: from imaging of drug efflux pumps to cellular drug targets.

Resistance of tumor cells to several structurally unrelated classes of natural products, including anthracyclines, taxanes, and epipodophyllotoxines, is often referred as multidrug resistance (MDR). This is associated with ATP-binding cassette transporters, which function as drug efflux pumps such as P-glycoprotein (Pgp) and multidrug resistance-associated protein 1 (MRP1). Because of the hypothesis in the early eighties that blockade of these efflux pumps by modulators would improve the effect of chemotherapy, extensive effort has been put to visualize these pumps using nuclear imaging with several specific tracers, using both SPECT and PET techniques. The methods and possibilities to visualize these pumps in both the tumor and the blood-brain barrier will be discussed. Because of the fact that the addition of Pgp or MRP modulators has not shown any clinical benefit in patient outcome, these specific MDR tracers are not routinely used in clinical practice. Evidence emerges that combination of chemotherapeutic drugs involved in MDR with the so-called targeted agents can improve patient outcome. The concept of molecular imaging can also be used to visualize the targets for these agents, such as HER2/neu and angiogenic factors such as vascular endothelial growth factor (VEGF). Potentially visualizing molecular drug targets in the tumor can function as biomarkers to support treatment decision for the individual patient.

Development and characterization of clinical-grade 89Zr-trastuzumab for HER2/neu immunoPET imaging.

UNLABELLED: The anti-human epidermal growth factor receptor 2 (HER2/neu) antibody trastuzumab is administered to patients with HER2/neu-overexpressing breast cancer. Whole-body noninvasive HER2/neu scintigraphy could help to assess and quantify the HER2/neu expression of all lesions, including nonaccessible metastases. The aims of this study were to develop clinical-grade radiolabeled trastuzumab for clinical HER2/neu immunoPET scintigraphy, to improve diagnostic imaging, to guide antibody-based therapy, and to support early antibody development. The PET radiopharmaceutical (89)Zr-trastuzumab was compared with the SPECT tracer (111)In-trastuzumab, which we have tested in the clinic already. METHODS: Trastuzumab was labeled with (89)Zr and (for comparison) with (111)In. The minimal dose of trastuzumab required for optimal small-animal PET imaging and biodistribution was determined with human HER2/neu-positive or -negative tumor xenograft-bearing mice. RESULTS: Trastuzumab was efficiently radiolabeled with (89)Zr at a high radiochemical purity and specific activity. The antigen-binding capacity was preserved, and the radiopharmaceutical proved to be stable for up to 7 d in solvent and human serum. Of the tested protein doses, the minimal dose of trastuzumab (100 microg) proved to be optimal for imaging. The comparative biodistribution study showed a higher level of (89)Zr-trastuzumab in HER2/neu-positive tumors than in HER2/neu-negative tumors, especially at day 6 (33.4 +/- 7.6 [mean +/- SEM] vs. 7.1 +/- 0.7 percentage injected dose per gram of tissue). There were good correlations between the small-animal PET images and the biodistribution data and between (89)Zr-trastuzumab and (111)In-trastuzumab uptake in tumors (R(2) = 0.972). CONCLUSION: Clinical-grade (89)Zr-trastuzumab showed high and HER2/neu-specific tumor uptake at a good resolution.

Robust, high-throughput LC-MS/MS method for therapeutic drug monitoring of cyclosporine, tacrolimus, everolimus, and sirolimus in whole blood.

The authors describe a fast, robust, and straightforward liquid chromatography and tandem mass spectrometry (LC-MS/MS) method with the use of a single LC-MS/MS system for cyclosporine A, tacrolimus, sirolimus, and everolimus in whole blood. The purpose of this method was to replace the immunoassay (IA) methods used in the laboratory of a hospital performing most organ transplantations (including heart, lung, liver, kidneys, bone marrow, and intestinal tract). Several LC-MS/MS methods have been described so far; however, most of them require complicated online extraction procedures. The described LC-MS/MS method uses a chromatographic gradient in combination with protein precipitation as sample preparation. The chromatographic method is capable of separating otherwise interfering peaks, with an analysis time of 2.6 minutes. Analyses were performed on a triple quadrupole LC-MS/MS system, with a C18 column held at 60 degrees C. Sample preparation required only 1 precipitation/dilution step. Sirolimus and everolimus are prepared and measured separately from tacrolimus and cyclosporine. During method development, it was found that the use of zinc sulfate provides process efficiency results of about 100% for tacrolimus and cyclosporine A, but only 81% and 87% for sirolimus and everolimus, respectively. With the developed sample preparation without zinc sulfate for sirolimus and everolimus, process efficiencies were 99% and 108%, respectively. The methods have been fully validated, and in a comparative study, patient samples were analyzed with IA and our developed LC-MS/MS methods. In the comparative studies, correlations (R2 values) of more than 0.85 were found between the IA and the new LC-MS/MS patient blood levels. There was a systematic deviation in blood levels measured by LC-MS/MS compared with IAs for cyclosporine A (17% lower than with immunoassay) and everolimus (30% lower than with IA). There seemed to be little or no systematic deviation for sirolimus and tacrolimus. The controls determined by the LC-MS/MS method over the past 10 months showed coefficient of variations of no more than 8.0% for each of the 4 immunosuppressants. In conclusion, the authors found the developed methods to be cost saving, more flexible, and more sensitive and that these methods have larger linear ranges than the previously used IA methods. The methods are already used for more than 20,000 patient samples in the daily routine, analyzing approximately 70 patient samples per day.

Immunoscintigraphy as potential tool in the clinical evaluation of HER2/neu targeted therapy.

Many new targeted anticancer drugs have been developed. In order for these drugs to be effective, the tumor target has to be present during treatment. Currently there are only a few biomarkers available to help the physician select the appropriate targeted drug for the patient and often tumor tissue is required for biomarker assays. Immunoscintigraphy might be able to improve diagnostic imaging, to guide antibody based therapy and to support early antibody development. Many different radiopharmaceuticals have been developed and used to visualize all kind of different targets especially in oncology. Intact radiolabeled antibodies generally show high tumor uptake but low tumor-to-blood ratios, particularly at early time points. Radiolabeled antibody fragments and proteins show widely differing values for tumor uptake and tumor-to-blood contrast. One of the promising targets for visualization might be HER2/neu. HER2/neu scans may prove useful for tumor staging, guiding of targeted therapy and measuring target occupancy in early drug development. Immunoscintigraphic clinical studies performed with intact antibodies indicate that HER2/neu imaging is feasible. Additional research will be performed to prove its value and make this technique applicable on a larger scale. The aim of this review is to describe the types of radiopharmaceuticals that are available, and the potential role of immunoscintigraphy in improving diagnostic imaging, guiding monoclonal antibody (mAb)-based therapy and supporting the development of mAb-based drugs using the HER2/neu target as an example.

Evaluation of RGD-targeted albumin carriers for specific delivery of auristatin E to tumor blood vessels.

Induction of apoptosis in endothelial cells is considered an attractive strategy to therapeutically interfere with a solid tumor's blood supply. In the present paper, we constructed cytotoxic conjugates that specifically target angiogenic endothelial cells, thus preventing typical side effects of apoptosis-inducing drugs. For this purpose, we conjugated the potent antimitotic agent monomethyl-auristatin-E (MMAE) via a lysosomal cleavable linker to human serum albumin (HSA) and further equipped this drug-albumin conjugate with cyclic c(RGDfK) peptides for multivalent interaction with alphavbeta3-integrin. The RGD-peptides were conjugated via either an extended poly(ethylene glycol) linker or a short alkyl linker. The resulting drug-targeting conjugates RGDPEG-MMAE-HSA and RGD-MMAE-HSA demonstrated high binding affinity and specificity for alphavbeta3-integrin expressing human umbilical vein endothelial cells (HUVEC). Both types of conjugates were internalized by endothelial cells and killed the target cells at low nM concentrations. Furthermore, we observed RGD-dependent binding of the conjugates to C26 carcinoma. Upon i.v. administration to C26-tumor bearing mice, both drug-targeting conjugates displayed excellent tumor homing properties. Our results demonstrate that RGD-modified albumins are suitable carriers for cell selective intracellular delivery of cytotoxic compounds, and further studies will be conducted to assess the antivascular and tumor inhibitory potential of RGDPEG-MMAE-HSA and RGD-MMAE-HSA.

Delivery of the p38 MAPkinase inhibitor SB202190 to angiogenic endothelial cells: development of novel RGD-equipped and PEGylated drug-albumin conjugates using platinum(II)-based drug linker technology.

Endothelial cells play an important role in inflammatory disorders, as they control the recruitment of leukocytes into inflamed tissue and the formation of new blood vessels. Activation of p38MAP kinase results in the production of proinflammatory cytokines and the expression of adhesion molecules. P38MAP kinase inhibitors are therefore considered important candidates for the treatment of inflammatory disorders. In the present study, we propose a novel strategy to counteract these processes by delivery of the p38MAP kinase inhibitor SB202190 into angiogenic endothelial cells. A drug-targeting conjugate was developed by conjugation of SB202190 to human serum albumin (HSA) using a novel platinum-based linker. Specificity for angiogenic endothelial cells was introduced by conjugation of cyclic RGD-peptides via bifunctional polyethylene glycol linkers. The final products contained an average of nine SB202190 and six RGDPEG groups per albumin. The platinum-based linker displayed high stability in buffers and culture medium, but released SB202190 slowly upon competition with sulfur-containing ligands like glutathione. RGDPEG-SB-HSA bound to alpha(v3)-integrin expressing endothelial cells (human umbilical cord vein endothelial cells) with low nanomolar affinity and was subsequently internalized. When HUVEC were treated with TNF to induce inflammatory events, pretreatment with RGDPEG-SB-HSA partially inhibited proinflammatory gene expression (IL-8, E-selectin; 30% inhibition) and secretion of cytokines (IL-8, 34% inhibition). We conclude that the developed RGDPEG-SB-HSA conjugates provide a novel means to counteract inflammation disorders such as rheumatoid arthritis.

New positron emission tomography tracer [(11)C]carvedilol reveals P-glycoprotein modulation kinetics.

Imaging of P-glycoprotein (P-gp) function in the blood-brain barrier (BBB) may support development of strategies, which will improve drug delivery to the brain. [(11)C]verapamil has been developed as a positron emission tomography (PET) tracer, to image P-gp function in vivo. Ideally, for the purpose of brain imaging, tracers should have a log P between 0.9 and 2.5. The beta-receptor antagonist carvedilol is a P-gp substrate with a log P=2.0, and can be labeled with [(11)C]. The aim of this study was to determine whether the P-gp substrate [(11)C]carvedilol can be used as a PET tracer for visualisation and quantification of the P-gp function in the BBB. Cellular [(11)C]carvedilol accumulation in GLC(4), GLC(4)/P-gp, and GLC(4)/Adr cells increased three-fold in the GLC(4)/P-gp cells after pretreatment with cyclosporin A (CsA) whereas no effect of MK571 could be determined in the GLC(4)/Adr cells. Ex vivo [(11)C]carvedilol biodistribution studies showed that [(11)C]carvedilol uptake in the brain was increased by CsA. [(11)C]carvedilol uptake in other organs was not affected by CsA. Autoradiography studies of rat brains showed that [(11)C]carvedilol was homogeneously distributed over the brain and that pretreatment with CsA increased [(11)C]carvedilol uptake. In vivo PET experiments were performed with and without P-gp modulation by CsA. P-gp mediated transport was quantified by Logan analysis of the PET data, calculating the distribution volume (DV) of [(11)C]carvedilol in the brain. Logan analysis resulted in excellent fits, revealing that [(11)C]carvedilol is not trapped in the brain. Brain DV of [(11)C]carvedilol showed a dose-dependent increase of maximal three-fold after CsA pretreatment. Above 15 mg kg(-1), no change in DV was found. Compared to [(11)C]verapamil less CsA was needed to reach maximal DV, suggesting that [(11)C]carvedilol kinetics is a more sensitive tool to in vivo measure P-gp function.