Raimar Löbenberg

Evaluation of Various Dissolution Media for Predicting In Vivo Performance of Class I and II Drugs

AbstractPurpose. In this paper we seek to verify the differences in dissolution behavior between class I and class II drugs and to evaluate the suitability of two new physiologically based media, of Simulated Gastric Fluid (SGF) and of milk for their ability to forecast trends in the in vivo performance of class II compounds and their formulations. Methods. Dissolution behavior of two class I drugs, i,e, acetaminophen and metoprolol, and of three class II drugs, i.e. danazol, mefenamic acid and ketoconazole, was studied with USP Apparatus 2 in water, SGF, milk, Simulated Intestinal Fluid without pancreatin (SIFsp) and in two media simulating the small intestinal contents in the fed (FeSSIF) and fasted (FaSSIF) states, respectively. Results. Class I powders dissolved rapidly in all media tested. Acetaminophen dissolution in milk was slow from one tablet formulation, in all other cases dissolution was more than 85% complete in 15 minutes. The dissolution rate of metoprolol was shown to be dependent on formulation and manufacturing method, and one of the three tablet formulations did not meet compendial specifications (80%/30 minutes). Dissolution behavior of class II drugs was greatly affected by choice of medium. Dissolution from a capsule formulation of danazol proved to be dependent on the concentration of solubilizing agents, with a the 30-fold increase in percentage dissolved within 90 minutes upon changing from aqueous media without surfactants to FaSSIF. Use of FeSSIF or milk as the dissolution medium resulted in an even greater increase in percentage dissolved, 100 and 180-fold respectively. Dissolution of the weak acid mefenamic acid from a capsule formulation is dependent on both pH and bile salt concentration, which leads to an offset between increased bile salt concentration and lower pH in the fed state compared to the fasted state medium. The weak base ketoconazole showed complete dissolution from a tablet formulation in Simulated Gastric Fluid without pepsin (SGFsp) within 30 minutes, 70% dissolution in 2 hours under fed state simulated upper jejunal conditions but only 6% dissolution in 2 hours under fasted state conditions. Conclusions. As predicted, dissolution of class II drugs proved to be in general much more dependent on the medium than class I drugs. With the array of compendial and physiological media available, it should be possible to design a suitable set of tests to predict the in vivo dissolution of both class I and II drugs from immediate release formulations.

Modern bioavailability, bioequivalence and biopharmaceutics classification system. New scientific approaches to international regulatory standards

In the last decade, the regulatory bioequivalence (BE) requirements of drug products have undergone major changes. The introduction of the biopharmaceutics drug classification system (BCS) into the guidelines of the Food and Drug Administration (FDA) is a major step forward to classify the biopharmaceutical properties of drugs and drug products. Based on mechanistic approaches to the drug absorption and dissolution processes, the BCS enables the regulatory bodies to simplify and improve the drug approval process. The knowledge of the BCS characteristics of a drug in a formulation can also be utilized by the formulation scientist to develop a more optimized dosage form based on fundamental mechanistic, rather than empirical, information. This report gives a brief overview of the BCS and its implications.

Targeted delivery of nanoparticles for the treatment of lung diseases

Targeted delivery of drug molecules to organs or special sites is one of the most challenging research areas in pharmaceutical sciences. By developing colloidal delivery systems such as liposomes, micelles and nanoparticles a new frontier was opened for improving drug delivery. Nanoparticles with their special characteristics such as small particle size, large surface area and the capability of changing their surface properties have numerous advantages compared with other delivery systems. Targeted nanoparticle delivery to the lungs is an emerging area of interest. This article reviews research performed over the last decades on the application of nanoparticles administered via different routes of administration for treatment or diagnostic purposes. Nanotoxicological aspects of pulmonary delivery are also discussed.

Interaction of Poly(butylcyanoacrylate) Nanoparticles with the Blood-Brain Barrier in vivo and in vitro

Poly(butylcyanoacrylate) nanoparticles were produced by emulsion polymerisation and used either uncoated or overcoated with polysorbate 80 (Tween® 80). [3H]-dalargin bound to nanoparticles overcoated with polysorbate 80 or in the form of saline solution was injected into mice and the brain concentrations of radioactivity determined. Statistically significant, three-fold higher brain concentrations with the nanoparticle preparations were obtained after 45 minutes, the time of greatest pharmacological response assessed as analgesia in previous experiments. In addition the brain inulin spaces in rats and the uptake of fluoresceine isothiocyanate labelled nanoparticles in immortalised rat cerebral endothelial cells, (RBE4) were measured. The inulin spaces after i.v. injection of polysorbate 80-coated nanoparticles were significantly increased by 1% compared to controls. This is interpreted as indicating that there is no large scale opening of the tight junctions of the brain endothelium by the polysorbate 80-coated nanoparticles. In in vitro experiments endocytic uptake of fluorescent nanoparticles by RBE4 cells was only observed after polysorbate 80-overcoating, not with uncoated particles. These results further support the hypothesis that the mechanism of blood-brain barrier transport of drugs by polysorbate 80-coated nanoparticles is one of endocytosis followed by possible transcytosis. The experiments were conducted in several laboratories as part of an EEC/INTAS collaborative program. For various procedural and regulatory reasons this necessitated the use of both rats and mice as experimental animals. The brain endothelial cell line used for the in vitro studies is the rat RBE4.

Physicochemical Characterization of Solid Dispersions of Indomethacin with PEG 6000, Myrj 52, Lactose, Sorbitol, Dextrin, and Eudragit® E100

The purpose of this study was to prepare and characterize solid dispersions of indomethacin with polyethylene glycol (PEG) 6000, Myrj 52, Eudragit® E100, and different carbohydrates such as lactose, mannitol, sorbitol, and dextrin. Indomethacin is a class II substance according to the Biopharmaceutics Classification System. It is a poorly water soluble antirheumatic agent. The goal was to investigate whether the solid dispersion can improve the dissolution properties of indomethacin. The solid dispersions were prepared by three different methods depending on the type of carrier. The evaluation of the properties of the dispersions was performed using solubility measurements, dissolution studies, Fourier‐transform infrared spectroscopy, and x‐ray powder diffractometery. The results indicate that lactose, mannitol, sorbitol, and especially Myrj 52 are suitable carriers to enhance the in vitro dissolution rate of indomethacin at pH 7.2. Eudragit E100, Myrj 52, and mannitol increase the dissolution properties at pH 1.2. The data from the x‐ray diffraction showed that the drug was still detectable in its solid state in all solid dispersions except solid dispersions with dextrin and high amounts of mannitol. However, the results from infrared spectroscopy together with those from x‐ray diffraction showed well‐defined drug–carrier interactions for dextrin coevaporates.

Inhalable nanoparticles, a non-invasive approach to treat lung cancer in a mouse model

Doxorubicin-loaded nanoparticles (NPs) were incorporated into inhalable effervescent and non-effervescent carrier particles using a spray-freeze drying technique. The prepared inhalable powders were tested in a tumor bearing Balb/c mouse model. Control mice were treated with blank inhalable NPs, inhalable lactose powder containing free doxorubicin, and intravenous injections of a suspension of doxorubicin NPs, doxorubicin solution, or saline solution. The survival of treatment groups was plotted with Kaplan-Meier curves. Animals treated with inhalable effervescent nanoparticle powder containing 30μg doxorubicin showed a highly significant improvement in survival compared to all other treatment groups. Mice in control groups treated with doxorubicin solution or doxorubicin NPs as intravenous injection, died in less than 50 days. Inhalable free doxorubicin showed high cardiac toxicity. Pathological samples showed large tumor masses in the lungs of animals not treated or treated with i.v. injections of doxorubicin NPs or doxorubicin solution. The lungs of animals treated with inhalable effervescent doxorubicin NPs showed fewer and much smaller tumors compared to the control groups, as visualized by MRI imaging which confirmed the observed pathology results. The present study demonstrates that inhalable effervescent doxorubicin NPs are an effective way to treat lung cancer. This non-invasive route of administration might change the way lung cancer is treated in the future.

Body distribution of azidothymidine bound to hexyl-cyanoacrylate nanoparticles after i.v. injection to rats.

Cells of the reticuloendothelial system (RES e.g. macrophages) play an important role in the immunopathogenesis of AIDS. The objective of the present study was to investigate the possibility of specifically targeting antiviral drugs such as azidothymidine (AZT) to macrophages using nanoparticles as colloidal drug carriers. In a first series of experiments the body distribution of 14C-labelled AZT bound to nanoparticles and a similarly prepared control solution with unbound AZT were studied in rats after intravenous injection. In a second series of experiments polysorbate 80-coated nanoparticles and a solution of AZT in saline were tested. 14C-labelled AZT was bound to nanoparticles using the surfactant bis(2-ethylhexyl) sulphosuccinate sodium (DOSS). The radioactivity in several organs, including those containing large numbers of macrophages, was measured after intravenous injection of the AZT-nanoparticles and the AZT-control solutions. AZT concentrations were up to 18 times higher in organs belonging to the RES if the drug was bound to nanoparticles compared with unbound AZT. These results demonstrate that nanoparticles are a potential drug targeting system for anti-AIDS drugs. The increase in drug concentration at the sites containing abundant macrophages may allow a reduction in dosage to reduce systemic toxicity.

Influence of the surfactant concentration on the body distribution of nanoparticles.

The rapid reticuloendothelial system (RES) uptake of nanoparticles after i.v. injection, especially by the liver, can be reduced and the body distribution can be altered by coating them with non-ionic surfactants. In the present work 2-14C-poly(methyl methacrylate) nanoparticles were coated with poloxamine 908 and polysorbate 80, and the influence of different surfactant concentrations on the body distribution was investigated. These surfactants were chosen because earlier studies showed that poloxamine 908 was very effective in decreasing the liver uptake and keeping the nanoparticles in circulation, whereas polysorbate 80 was the most effective surfactant to direct the particles to organs that do not belong to the RES. Above nanoparticles were injected i.v. to rats and the animals were sacrificed after 30 min. Below a surfactant concentration of 0.1% the nanoparticle preparations behaved like uncoated particles. At a 0.1% concentration a very sudden and significant change in the body distribution occurred with poloxamine 908. The liver concentration decreased from about 75% of the dose to 13% and stayed at this level at higher surfactant concentrations. This decrease was combined with a similar sudden complementary increase in blood and other organ and tissue concentrations. With polysorbate 80 the decrease in liver concentration and increase in the blood and the other organ levels was gradual and became important only above 0.5% surfactant concentration. The results indicate that the type of interaction and the strength of the adsorptive binding to the nanoparticles are different with different surfactants. This in turn leads to different body distribution patterns after i.v. injection of surfactant coated nanoparticles.

Dissolution Testing as a Prognostic Tool for Oral Drug Absorption: Dissolution Behavior of Glibenclamide

Purpose. The dissolution behavior of two commercially availableglibenclamide formulations was tested in various media. The aim of thestudy was to investigate whether the use of biorelevant dissolutionmedia (BDM) would be advantageous over the use of standard mediafor predicting the in vivo performance of the two formulations.Methods. The dissolution tests were performed using USP 23 apparatus2. Conventional buffers and USP media were compared with two BDMcontaining different amounts of lecithin and sodium taurocholate.Results. The dissolution of two drug powders was highly dependenton wetting, particle size, pH, and the composition of the mediumused. In addition, the dissolution behavior of the two glibenclamideformulations showed differences in all media tested. The dissolutionresults of the two formulations were compared with those from anin vivo bioequivalence study undertaken by the central quality controllaboratory of the German pharmacists (ZL). The bioequivalencecriterion set by the ZL requires more than 80;pc drug release within 10minutes. Results in FaSSIF, one of the BDMs, met the ZL criterionand this medium was also able to discriminate between the twoformulations. This was not the case for the other media tested.Conclusions. The study indicates that BDM are better able to discriminatebetween glibenclamide formulations than standard dissolutionmedia.

Optimization of a two-step desolvation method for preparing gelatin nanoparticles and cell uptake studies in 143B osteosarcoma cancer cells.

PURPOSE To establish a matrix of parameters to synthesize nanoparticles of different sizes and to investigate the cellular uptake of these nanoparticles by osteosarcoma cancer cells in order to investigate their potential as therapeutic drugdelivery carriers. METHODS Gelatin A and B were used to synthesize nanoparticles by a two-step desolvation process. Different parameters were investigated, including temperature, pH, concentration of glutaraldehyde, type of desolvating agent and nature of gelatin. For cell uptake studies, Texas Red labeled nanoparticles were incubated with 143B osteosarcoma cells and then evaluated using confocal laser scanning microscopy (CLSM). RESULTS The systematic investigation of the synthesis parameters showed that it is possible to prepare gelatin-based nanoparticles with different particle sizes and a narrow size distribution. Temperature and nature of the gelatin were the most important synthesis factors. Bioimaging using CLSM showed uptake of the nanoparticles by 143B osteosarcoma cancer cells. CONCLUSIONS Osteosarcoma cancer cells take up gelatin nanoparticles. This might improve the clinical effectiveness of anti-cancer treatments if nanoparticles are used as a drug delivery system and has important implications for future cancer treatment strategies.