Physiological relevance of in-vitro cell-nanoparticle interaction studies as a predictive tool in cancer nanomedicine research.

Cell uptake study is a routine experiment used as a surrogate to predict in vivo response in cancer nanomedicine research. Cell culture conditions should be designed in such a way that it emulates 'real' physiological conditions and avoid artefacts. It is critical to dissect the steps involved in cellular uptake to understand the physical, chemical, and biological factors responsible for particle internalization. The two-dimensional model (2D) of cell culture is overly simplistic to mimic the complexity of cancer tissues that exist in vivo. It cannot simulate the critical tissue-specific properties like cell-cell interaction and cell-extracellular matrix (ECM) interaction and its influences on the temporal and spatial distribution of nanoparticles (NPs). The three dimensional model organization of heterogenous cancer and normal cells with the ECM acts as a formidable barrier to NP penetration and cellular uptake. The three dimensional cell culture (3D) technology is a breakthrough in this direction that can mimic the barrier properties of the tumor microenvironment (TME). Herein, we discuss the physiological factors that should be considered to bridge the translational gap between in and vitro cell culture studies and in-vivo studies in cancer nanomedicine.

An innovative in situ method of creating hybrid dendrimer nano-assembly: An efficient next generation dendritic platform for drug delivery.

Dendrimers have proven to be effective for drug delivery and their biodisposition varies with change on their surface, generation and core. In an effort to understand the role of critical nanoscale design parameters, we developed a novel hybrid dendrimer approach to harness unique features of individual dendrimers and create a nano-assembly. We report an easy in situ method of creating hybrid dendrimer nano-assembly by mixing G4.0 PAMAM (-NH2) and G3.5 PAMAM (-COONa) dendrimers with a chemotherapeutic drug docetaxel (DTX). Zeta potential, HR-TEM, 1H-NMR proved the formation of nano-assembly. In vitro dissolution, release studies revealed pH dependent dissolution and sustained drug release. Cellular uptake, cytotoxicity, and flow cytometric analysis in human/mouse glioblastoma cells indicated the effectiveness of hybrid dendrimers. The oral administration of the hybrid dendrimers showed pharmacokinetic equivalence to intravenous injection of commercially available Taxotere®. Hybrid dendrimer concept provides much needed fine-tuning to create multistage next-generation dendritic platform in nanomedicine.

Dendrimers for Drug Delivery.

Dendrimers have come a long way in the last 25 years since their inception. Originally created as a wonder molecule of chemistry, dendrimer is now in the fourth class of polymers. Dr. Donald Tomalia first published his seminal work on Poly(amidoamine) (PAMAM) dendrimers in 1985. Application of dendrimers as a drug delivery system started in late 1990s. Dendrimers for drug delivery are employed using two approaches: (i) formulation and (ii) nanoconstruct. In the formulation approach, drugs are physically entrapped in a dendrimer using non-covalent interactions, whereas drugs are covalently coupled on dendrimers in the nanoconstruct approach. We have demonstrated the utility of PAMAM dendrimers for enhancing solubility, stability and oral bioavailability of various drugs. Drug entrapment and drug release from dendrimers can be controlled by modifying dendrimer surfaces and generations. PAMAM dendrimers are also shown to increase transdermal permeation and specific drug targeting. Dendrimer platforms can be engineered to attach targeting ligands and imaging molecules to create a nanodevice. Dendrimer nanotechnology, due to its multifunctional ability, has the potential to create next generation nanodevices.

Development of a Topical Resveratrol Formulation for Commercial Applications Using Dendrimer Nanotechnology.

Resveratrol (RSV) is well known for its anti-oxidant and anti-aging properties. However, resveratrol is insoluble in water and has stability issues. Recently, efforts were placed to prepare a resveratrol-based advanced anti-aging topical product but it contains harsh organic solvents and oils that could be harmful to the human body and the environment. Hence, we propose the use of a multifunctional dendrimer to solve the solubility and stability issues of resveratrol. A dendrimer-resveratrol complex was prepared, optimized and tested for solubility enhancement, stability in solution and cream dosage forms. We have also developed a high performance liquid chromatography method to measure the resveratrol within the final product. PAMAM dendrimers increased the solubility and stability of resveratrol in water and semisolid dosage forms. Therefore, this product would be water based 'green' formulation devoid of harsh organic solvents and oils and can be safely applied to the skin. Additionally, we have shown that the dendrimer helped to increase overall RSV loading and skin penetration of resveratrol. The dendrimer-RSV formulation was successfully scaled up towards commercialization. Dendrimer with RSV has led to an innovation in anti-aging cream and solutions that could be commercially marketed. Dendrimer-RSV complex could also be added to other product forms for additional purposes and applications.

Poly (amidoamine) dendrimer-mediated hybrid formulation for combination therapy of ramipril and hydrochlorothiazide.

We present a dendrimer-based hybrid formulation strategy to explore the potential of poly (amidoamine) PAMAM dendrimers to be used as drug carriers for combination therapy of an anti-hypertensive drug ramipril (RAPL) and a diuretic hydrochlorothiazide (HCTZ). The drug-dendrimer complexes were prepared by phase-equilibration method. The results showed that the solubility of RAPL and HCTZ was dependent on dendrimer concentration and pH of dendrimer solution. The solubility profile of both RAPL and HCTZ dendrimer complexes illustrated a non-linear relationship with dendrimer concentration. At 0.8% (w/v) dendrimer concentration, solubility of RAPL was increased 4.91 folds with amine-terminated while for HCTZ, solubility enhancement was highest (3.72 folds) with carboxy-terminated. The complexes were characterized by Fourier transform infrared spectroscopy, nuclear magnetic resonance analysis and high performance liquid chromatography. In-vitro drug dissolution performance of pure drugs, individual drug loaded dendrimer formulations and hybrid formulations was studied in USP dissolution medium (pH7.0) and in simulated gastric fluid (pH1.2). Dendrimer mediated formulations showed faster and complete dissolution compared to pure RAPL or HCTZ. Surprisingly, similar pattern of dissolution profile was established with hybrid formulations as compared to individual drug loaded dendrimers. The dendrimer-based hybrid formulations were found to be stable at dark and refrigerated conditions up to 5weeks. Conclusively, the proposed formulation strategy establishes a novel multitasking platform using dendrimer for simultaneous loading and delivery of multiple drugs for pharmaceutical applications.

siRNA Therapy, Challenges and Underlying Perspectives of Dendrimer as Delivery Vector.

siRNA technology presents a helpful means of gene silencing in mammalian cells. Advancement in the field includes enhanced attentiveness in the characterization of target and off-target effects employing suitable controls and gene expression microarrays. These will permit expansion in the measurement of single and multiple target combinations and also permit comprehensive efforts to understand mammalian cell processes. Another fact is that the delivery of siRNA requires the creation of a nanoparticulate vector with controlled structural geometry and surface modalities inside the targeted cells. On the other hand, dendrimers represent the class of carrier system where massive control over size, shape and physicochemical properties makes this delivery vector exceptional and favorable in genetic transfection applications. The siRNA therapeutics may be incorporated inside the geometry of the density controlled dendrimers with the option of engineering the structure to the specific needs of the genetic material and its indication. The existing reports on the siRNA carrying and deliverance potential of dendrimers clearly suggest the significance of this novel class of polymeric architecture and certainly elevate the futuristic use of this highly branched vector as genetic material delivery system.

Dendrimer nanotechnology for enhanced formulation and controlled delivery of resveratrol.

In spite of its wide and beneficial pharmacological potential, resveratrol lags behind other compounds because of its comparatively less impressive pharmacokinetic profile. Resveratrol has very low oral bioavailability and, from a formulation perspective, it has low solubility in water, which leads to its poor absorption upon oral administration. Apart from low aqueous solubility, resveratrol has poor metabolic stability and instability at high pH, and is photosensitive. The pharmacokinetic and formulation-related limitations of resveratrol can be controlled by entrapping the small resveratrol molecule inside highly water-soluble poly(amidoamine) dendrimer nanostructures, which provide spherical architecture and polyvalency at the nanoscale level, thus leading to novel features. Dendrimer architecture is used to entrap resveratrol for enhancement of its solubility and stability in aqueous solution; they can be engineered to control pharmacokinetics and targeting for oral, mucosal, transdermal, or parenteral administration. Dendrimers have the potential to work as excipients with multifunctional capability by enhancing solubility, dissolution, stability, permeability, multiple drug/cosmetic entrapment, controlled delivery, bioavailability, and efficacy of drugs.

Brain Targeting of a Water Insoluble Antipsychotic Drug Haloperidol via the Intranasal Route Using PAMAM Dendrimer.

Delivery of therapeutics to the brain is challenging because many organic molecules have inadequate aqueous solubility and limited bioavailability. We investigated the efficiency of a dendrimer-based formulation of a poorly aqueous soluble drug, haloperidol, in targeting the brain via intranasal and intraperitoneal administration. Aqueous solubility of haloperidol was increased by more than 100-fold in the developed formulation. Formulation was assessed via different routes of administration for behavioral (cataleptic and locomotor) responses, and for haloperidol distribution in plasma and brain tissues. Dendrimer-based formulation showed significantly higher distribution of haloperidol in the brain and plasma compared to a control formulation of haloperidol administered via intraperitoneal injection. Additionally, 6.7 times lower doses of the dendrimer-haloperidol formulation administered via the intranasal route produced behavioral responses that were comparable to those induced by haloperidol formulations administered via intraperitoneal injection. This study demonstrates the potential of dendrimer in improving the delivery of water insoluble drugs to brain.

Dendrimer-stabilized smart-nanoparticle (DSSN) platform for targeted delivery of hydrophobic antitumor therapeutics.

PURPOSE: To formulate dendrimer-stabilized smart-nanoparticle (DSSN; pD-ANP-f) for the targeted delivery of the highly hydrophobic anticancer drug, Paclitaxel (PTXL). METHOD: The developed nanoformulations were evaluated for particle size, surface-charge, loading efficiency, particle density, in-vitro drug release, SEM/TEM, cytotoxicity assay, fluorescence uptake, HPLC quantitative cell uptake assay, flow cytometry, tubulin polymerization, and stability assessments. RESULTS: The developed pD-ANP-f nanoformulation (135.17 ± 7.39 nm; -2.05 ± 0.37 mV and 80.11 ± 4.39% entrapment) exhibited a pH-dependent drug release; remained stable in physiological pH, while rapid releasing PTXL under tumorous environment (pH 5.5). The cytotoxicity assay performed in cervical, breast, blood, and liver cancer cell lines showed pD-ANP-f to be strongly suppressing the growth of cancer cells. We investigated the fluorescence based intracellular trafficking and HPLC based cellular uptake of nanoformulated drug and the result indicates higher cellular uptake of pD-ANP-f compared to other formulations. pD-ANP-f prominently induced apoptosis (73.11 ± 3.84%) and higher polymerization of tubulins (59.73 ± 6.22%). DSSN nanoformulation was found to be extremely biocompatible (<1% hemolytic) compared to naked PTXL (19.22 ± 1.01%) as well as PTXL-dendrimer nanocomplex (8.29 ± 0.71%). CONCLUSION: DSSN strategy is a novel and promising platform for biomedical applications that can be effectively engaged for the delivery of drug/gene/siRNA targeting.

Optimization of carboxylate-terminated poly(amidoamine) dendrimer-mediated cisplatin formulation.

Abstract Cisplatin is mainly used in the treatment of ovarian, head and neck and testicular cancer. Poor solubility and non-specific interactions causes hurdles in the development of successful cisplatin formulation. There were few reports on poly(amidoamine) (PAMAM) dendrimer-cisplatin complexes for anticancer treatment. But the earlier research was mainly focused on therapeutic effect of PAMAM dendrimer-cisplatin complex, with less attention paid on the formulation development of these complexes. Objective of the present study is to optimize and validate the carboxylate-terminated, EDA core PAMAM dendrimer-based cisplatin formulation with respect to various variables such as dendrimer core, generation, drug entrapment, purification, yield, reproducibility, stability, storage and in-vitro release. Dendrimer-cisplatin complex was prepared by an efficient method which significantly increases the % platinum (Pt) content along with the product yield. Dendrimers showed reproducible (∼27%) platinum loading by weight. Variation in core and generations does not produce significant change in the % Pt content. Percentage Pt content of dendrimeric formulation increases with increase in drug/dendrimer mole ratio. Formulation with low drug/dendrimer mole ratio showed delayed release compared to the higher drug/dendrimer mole ratio; these dendrimer formulations are stable in room temperature. In vitro release profiles of the stored dendrimer-cisplatin samples showed comparatively slow release of cisplatin, which may be due to formation of strong bond between cisplatin and dendrimer. This study will contribute to create a fine print for the formulation development of PAMAM dendrimer-cisplatin complexes.

Pharmacokinetic and pharmacodynamic studies of poly(amidoamine) dendrimer based simvastatin oral formulations for the treatment of hypercholesterolemia.

The aim of this investigation was to evaluate the in vivo potential of poly(amidoamine) dendrimers (PAMAM) based simvastatin (SMV) formulations as nanoscale drug delivery units for controlled release action of simvastatin. Drug-dendrimer complexes were prepared and characterized by Fourier transform infrared (FTIR) spectroscopy. In a pharmacodynamic study, the percent increase in cholesterol was less with PAMAM dendrimer formulations as compared to pure drug. The cholesterol level was increased to 20.92% with pure SMV, whereas it was 11.66% with amine dendrimer, 11.49% with PEGylated dendrimer, and 10.86% with hydroxyl dendrimer formulations. Reduction in the increase in triglyceride and low density lipoprotein level was also more prominent with the drug-dendrimer formulations. The order of increase in high density lipoprotein level was PEGylated PAMAM-SMV (4.04%) > PAMAM-amine-SMV (2.57%) > PAMAM-hydroxyl-SMV (1.48%) > pure SMV (1.09%). Dendrimer-SMV formulations showed better pharmacokinetic performances than pure SMV suspension. The peak plasma SMV concentration increased from 2.3 µg/mL with pure SMV to 3.8 µg/mL with dendrimer formulations. The dendrimer mediated formulation had 3-5 times more mean SMV residence time than pure SMV. Furthermore, SMV absorption and elimination rates were decreased significantly, showing controlled release of SMV from the dendrimer formulations.

Development and optimization of thiolated dendrimer as a viable mucoadhesive excipient for the controlled drug delivery: an acyclovir model formulation.

In the present study we report the development of novel thiolated dendrimers for mucoadhesive drug delivery. The thiolated dendrimers were synthesized by conjugating PAMAM dendrimer (G3.5)with cysteamine at two different molar ratios, i.e. 1:30 (DCys1) and 1:60 (DCys2). The thiolated dendrimers were further encapsulated with acyclovir (DCys1Ac and DCys2Ac) and the conjugates were characterized for thiol content, drug loading, drug release, and mucoadhesive behavior. The thiolated dendrimer conjugates showed thiol content of 10.56 ± 0.34 and 68.21 ± 1.84 µM/mg of the conjugate for DCys1 and DCys2, respectively. The acyclovir loading was observed to be highest in dendrimer drug conjugate (DAc) compared to other DCys1Ac and DCys2Ac conjugates. The thiolated dendrimers showed sustained release of acyclovir and showed higher mucoadhesion. The in vitro mucoadhesive activity of DCys2Ac was 1.53 and 2.89 fold higher mucoadhesion compared to DCys1Ac and DAc, respectively. These results demonstrated the usefulness of thiolated dendrimers as a mucoadhesive carrier and represent a novel platform for drug delivery. FROM THE CLINICAL EDITOR: This study demonstrates the utility of thiolated dendrimers as mucoadhesive carriers as reported in an acyclovir delivery model system.

Performance evaluation of PAMAM dendrimer based simvastatin formulations.

The purpose of this investigation was to evaluate the performance of poly (amidoamine) (PAMAM) dendrimers, with three different surface groups, to be used as drug carriers. Drug-dendrimers complexes were investigated for solubility studies, dissolution studies, in vitro drug release studies, and for stability studies. The solubility enhancement was found maximum with PEGylated dendrimers (33 times) followed by amine (23 times) and hydroxyl (17.5 times) dendrimers. The solubility profile of simvastatin-dendrimer complex showed a linear correlation (Higuchi A(L)-type diagram) between solubility and dendrimers concentration. The formation of the complexes between drug molecules and dendrimers were characterized by the FTIR spectra of these complexes, showing the appearance of the bond formed between the functional groups of the drug (OH and COOH) and dendrimers (NH(2) and OH). The drug-dendrimer complexes displayed the controlled release action during in vitro release studies. Pure simvastatin (SMV) was released in 5h whereas the PEGylated dendrimers-SMV complexes released the drug up to 5 days. The non-PEGylated formulations released the drug up to 24h. Formulations with amine and PEGylated dendrimers were subjected to accelerated stability studies. Formulations with amine dendrimers were found to be most stable in dark, low temperature (0°C) whereas the dark, RT was most suitable storage conditions for formulation with PEGylated dendrimers.

Unexpected in vivo anti-inflammatory activity observed for simple, surface functionalized poly(amidoamine) dendrimers.

We report unexpected anti-inflammatory properties for naked, unmodified poly(amidoamine) (PAMAM) dendrimers bearing simple surface functionality (e.g., -NH(2), -OH, etc.). This property was discovered serendipitously while studying the drug delivery features of PAMAM dendrimer-indomethacin complexes. Activity was quantitated by using three independently recognized in vivo anti-inflammatory assay methods, namely, (1) the carrageenan-induced paw edema model (acute activity), (2) the cotton pellet test, and (3) the adjuvant-induced arthritis assay in rats (chronic activities). Those dendrimers bearing amine or hydroxyl surface groups exhibited significant anti-inflammatory activity in the carrageenan-induced paw edema model. For example, [core: 1,2-diaminoethane]; (G = 4.0); {dendri-poly(amidoamine)-(NH(2))(64)} (i.e., G4-NH(2)) exhibited a mean percent inhibition of 35.50 +/- 1.6% 3 h after administration and [core: 1,2-diaminoethane] (G = 4.0); {dendri-poly(amidoamine)-(OH)(64)} (i.e., G4-OH) gave a mean percent inhibition of 31.22 +/- 1.58% 3 h after administration. On the other hand, [core: 1,2-diaminoethane] (G = 4.5); {dendri-poly(amidoamine)-(CO(2)H)(128)} (i.e., G4.5-CO(2)H) exhibited mild anti-inflammatory activity with a mean percent inhibition of 14.00 +/- 2.5% 3 h after administration. Unexpectedly, G4-NH(2) showed significantly higher activity compared to naked indomethacin (i.e., 50 +/- 3.1% vs 22 +/- 1.2%) using the cotton pellet granuloma model. Similarly, in the adjuvant-induced arthritis model, G4-NH(2) compared to naked indomethacin gave a mean percent inhibition of 30 +/- 1.9% versus 11 +/- 0.9% 14 days after administration.

Dendrimers for enhanced drug solubilization.

Approximately 40% of newly developed drugs are rejected by the pharmaceutical industry and will never benefit a patient because of low water solubility. Another 17% of launched drugs exhibit suboptimal performance for the same reason. Given the growing impact and need for drug delivery, a thorough understanding of delivery technologies that enhance the bioavailability of drugs is important. The high level of control over the dendritic architecture (size, branching density, surface functionality) makes dendrimers ideal excipients for enhanced solubility of poorly water-soluble drugs. Many commercial small-molecule drugs with anticancer, anti-inflammatory and antimicrobial activity have been formulated successfully with dendrimers, such as poly(amidoamine) (PAMAM), poly(propylene imine) (PPI or DAB) and poly(etherhydroxylamine) (PEHAM). Some dendrimers themselves show pharmaceutical activity in these three areas, providing the opportunity for combination therapy in which the dendrimers serve as the drug carrier and simultaneously as an active part of the therapy.

Controlled systemic delivery of indomethacin using membrane-moderated, cream formulation-based transdermal devices.

The present study was carried out to design a viable and practically effective transdermal systems of indomethacin using cream-based drug reservoirs and suitable rate controlling membranes. As vehicles, a more lipophilic base (F(1)) and a cream formulation containing predominant aqueous phase (F(2)) were chosen to study the influence of vehicle nature and role of permeation enhancers that increases thermodynamic activity and to provide diffusible species of drug to skin. Rate controlling membranes of cellulose acetate (CA) and ethyl cellulose (EC) with polyvinyl pyrollidine and hydroxypropyl methyl cellulose were used to design transdermal devices. In vivo, effective plasma concentrations of indomethacin are maintained up to 24 hr whereas oral formulation showed only up to 8 hr. Although the plasma drug levels between both EC films differ insignificantly, PVP film showed a better pharmacokinetic profile. The pharmacodynamic performance of the transdermal devices exhibited good anti-inflammatory activity over 24 hr compared with orally administered indomethacin. In vivo studies indicate the superiority of CA films over the EC films. Further, enhancement may be achieved with other classic enhancers/enhancement strategies with such devices containing aqueous cream vehicle and the optimum membranes.

Poly(amidoamine) (PAMAM) dendritic nanostructures for controlled site-specific delivery of acidic anti-inflammatory active ingredient.

The purpose of the investigation was to evaluate the potential of polyamidoamine (PAMAM) dendrimer as nanoscale drug delivery units for controlled release of water insoluble and acidic anti-inflammatory drug. Flurbiprofen (FB) was selected as a model acidic anti-inflammatory drug. The aqueous solutions of 4.0 generation (G) PAMAM dendrimer in different concentrations were prepared and used further for solubilizing FB. Formation of dendrimer complex was characterized by Fourier transform infrared spectroscopy. The effect of pH on the solubility of FB in dendrimer was evaluated. Dendrimer formulations were further evaluated for in vitro release study and hemolytic toxicity. Pharmacokinetic and biodistribution were studied in male albino rats. Efficacy of dendrimer formulation was tested by carrageenan induced paw edema model. It was observed that the loaded drug displayed initial rapid release (more than 40% till 3rd hour) followed by rather slow release. Pharmacodynamic study revealed 75% inhibition at 4th hour that was maintained above 50% till 8th hour. The mean residence time (MRT) and terminal half-life (THF) of the dendritic formulation increased by 2-fold and 3-fold, respectively, compared with free drug. Hence, with dendritic system the drug is retained for longer duration in the biosystem with 5-fold greater distribution. It may be concluded that the drug-loaded dendrimers not only enhanced the solubility but also controlled the delivery of the bioactive with localized action at the site of inflammation.

Solubility enhancement of indomethacin with poly(amidoamine) dendrimers and targeting to inflammatory regions of arthritic rats.

This work includes investigation on solubility enhancement of indomethacin (IND) in the presence of poly(amidoamine) (PAMAM) dendrimers and passive targeting of the PAMAM/IND complex so formed to the inflamed regions in an animal model. The complex formation was confirmed by infrared and (1)H nuclear magnetic resonance spectroscopy methods. Solubility of IND in aqueous G4-PAMAM followed Higuchi's A(N) curve depending on pH of the solubilizing medium. The solubility was decreased upon addition of dendrimer to the IND saturated solution at various pH, indicating aggregation behavior of the PAMAM/IND complex and conforming to the Higuchi's A(N) solubility profile. The in vitro release of IND from the PAMAM/IND complex through a cellophane membrane, from a Franz diffusion cell, showed 79 +/- 3.2% drug release in 24 h. The drug release was further retarded in the presence of human serum albumin (HSA) suggesting the significance of complex HSA binding in altering in vivo behavior of the complex. Intravenous administration of the PAMAM/IND complex formulation in rats showed a two-compartment pharmacokinetic profile. Enhanced effective IND concentrations in the inflamed regions were obtained for the prolonged time period with the PAMAM/IND complex compared to the free drug in arthritic rats indicating preferred accumulation of IND to the inflamed region. The targeting efficiency of PAMAM/IND complex was 2.29 times higher compared to free drug. In contrast to the previous investigations, two interesting findings reported here are: (a) solubility behavior of IND in G4-PAMAM dendrimer deviates from linearity with increasing concentrations of dendrimer at acidic to neutral pH values and (b) inspite of lymphatic drainage, retention of PAMAM/IND complexes occurs at the inflammatory site.

Dendrimer-mediated transdermal delivery: enhanced bioavailability of indomethacin.

The transdermal delivery of aqueous formulations of indomethacin, a model drug, with different concentrations of three types of dendrimer showed a linear increase in flux with increasing concentration of each of the dendrimers. This result was in contrast to phase solubility studies, where Higuchi's A(N) profile was observed. The steady-state flux of the drug increased significantly and was highest with the G4-NH2 dendrimer at 0.2% w/v concentration, which showed an enhancement factor of 4.5 compared to the pure drug suspension. In vivo, a steady-state flux was achieved in 5 h, and the C(max) values were significantly higher with G4-NH2 and G4-OH dendrimer formulations. The [AUC](0-24h) of G4-NH2 (2.27 times) and G4-OH (1.95 times) formulations were significantly higher than that of the pure drug, but was only marginally higher in the case of G-4.5 dendrimer formulation. The % inhibition of paw volume showed a trend comparable to the pharmacokinetic data and a maximum of 1.6- and 1.5-fold increase was found with G4-NH2 and G4-OH formulations, respectively, compared to the pure drug suspension.