Optimization of Dissolution Compartments in a Biorelevant Dissolution Apparatus Golem v2, Supported by Multivariate Analysis.

Biorelevant dissolution instruments represent an important tool for pharmaceutical research and development. These instruments are designed to simulate the dissolution of drug formulations in conditions most closely mimicking the gastrointestinal tract. In this work, we focused on the optimization of dissolution compartments/vessels for an updated version of the biorelevant dissolution apparatus-Golem v2. We designed eight compartments of uniform size but different inner geometry. The dissolution performance of the compartments was tested using immediate release caffeine tablets and evaluated by standard statistical methods and principal component analysis. Based on two phases of dissolution testing (using 250 and 100 mL of dissolution medium), we selected two compartment types yielding the highest measurement reproducibility. We also confirmed a statistically ssignificant effect of agitation rate and dissolution volume on the extent of drug dissolved and measurement reproducibility.

Dissolution and disintegration kinetics of high-active pharmaceutical granules produced at laboratory and manufacturing scale.

The effect of process scale-up from 4 to 400-L high-shear granulator on the release kinetics of the active ingredient from pharmaceutical granules has been investigated. The dissolution and disintegration rates of the granules were measured simultaneously by the combination of UV/vis spectroscopy and static light scattering. The granule batches were found to consist of sub-populations with qualitatively different dissolution behavior: "weaker" granules that disintegrated during dissolution, and "stronger" granules that retained their size and from which the active ingredient was gradually leached. The existence of these sub-populations was attributed to non-uniform distribution of normal and shear forces that prevail in granulators of different size. This hypothesis was confirmed by preparing granules at increasing values of the Froude number at the 4-L scale, and observing a transition from the break-up dissolution mode to the leaching dissolution mode with increasing granule densification. The simultaneous observation of solute concentration and particle size distribution during granules dissolution proved to be a useful tool for the understanding of dissolution mechanisms and for identifying non-uniformities of process conditions that can occur during scale-up.

ROLE OF THE INTERNATIONAL ORGANIZATIONS IN PREVENTING THE COUNTERFEIT MEDICINES ENTRY INTO THE WORLD MARKETS.

30 years have passed since Conference of Experts on the Rational Use of Drugs was held in Nairobi, Kenya, from 25 to 29 November 1985, where the problem of counterfeit medicines was mentioned as the international for the first time. The problem of counterfeit medicines is not only a major threat to public health and national and private economy, but also it is of great interest for key decision-making actors at the international level. The authors analyzed what has been done since that time by international organizations. Combating the counterfeiting of medicines cannot be successfully achieved by the health sector alone - World Health Organization (WHO), - so the efforts of the other United Nations (UN) organizations relevant to counterfeiting were in need and were studied in the article: World Intellectual Property Organization (WIPO), World Trade Organization (WTO), World Customs Organization (WCO), United Nations Office on Drugs and Crime (UNODC), etc. Today WHO is unable to coordinate all their activities, so the few existing proposals for establishing a new mechanism of international cooperation have been examined. Will the MEDICRIME Convention that will enter into force on January 1, 2016 be the start of the new era in the combating with the counterfeit medicines? - the authors offered their vision on the international developments.

Development of In Vitro-In Vivo Correlation/Relationship Modeling Approaches for Immediate Release Formulations Using Compartmental Dynamic Dissolution Data from "Golem": A Novel Apparatus.

Different batches of atorvastatin, represented by two immediate release formulation designs, were studied using a novel dynamic dissolution apparatus, simulating stomach and small intestine. A universal dissolution method was employed which simulated the physiology of human gastrointestinal tract, including the precise chyme transit behavior and biorelevant conditions. The multicompartmental dissolution data allowed direct observation and qualitative discrimination of the differences resulting from highly pH dependent dissolution behavior of the tested batches. Further evaluation of results was performed using IVIVC/IVIVR development. While satisfactory correlation could not be achieved using a conventional deconvolution based-model, promising results were obtained through the use of a nonconventional approach exploiting the complex compartmental dissolution data.

Advances in dissolution instrumentation and their practical applications.

The rising demands on discriminatory and prediction abilities of dissolution methods and the increasing complexity of new drug products are the main driving forces of the progress in this field. The research moves forward as imperfections and shortcomings of classical methods are being described, and where the capabilities of the contemporary methods are insufficient, new methods are being developed. The review discusses these advances with respect to the issues that currently draw the most attention, i.e. correct simulation of hydrodynamics and stress forces, maintenance of sink conditions, study of precipitation, use of biorelevant media and the employment of more physiologically relevant methods in general.

New polyfluorothiopropanoyloxy derivatives of 5ß-cholan-24-oic acid designed as drug absorption modifiers.

A series of final six propanoyloxy derivatives of 5ß-cholan-24-oic acid (tridecafluoroctylsulfanyl- and tridecafluoroctylsulfinylethoxycarbonylpropanoyloxy derivatives) as potential drug absorption promoters (skin penetration enhancers, intestinal absorption promoters) was generated by multistep synthesis. Structure confirmation of all generated compounds was accomplished by (1)H NMR, (13)C NMR, IR and MS spectroscopy methods. All the prepared compounds were analyzed using RP-TLC, and their lipophilicity (RM) was determined. The hydrophobicity (log P), solubility (logS), polar surface area (PSA) and molar volume (MV) of the studied compounds were also calculated. All the target compounds were tested for their in vitro transdermal penetration effect and as potential intestinal absorption enhancers. The cytotoxicity of all the evaluated compounds was evaluated against normal human skin fibroblast cells. Their anti-proliferative activity was also assessed against human cancer cell lines: T-lymphoblastic leukaemia cell line and breast adenocarcinoma cell line. One compound showed high selective cytotoxicity against human skin fibroblast cells and another compound possessed high cytotoxicity against breast adenocarcinoma cell line and skin fibroblast cells. Only one compound expressed anti-proliferative effect on leukaemia and breast adenocarcinoma cells without affecting the growth of normal cells, which should be promising in potential development of new drugs. Most of the target compounds showed minimal anti-proliferative activity (IC50>37µM), indicating they would have moderate cytotoxicity when administered as chemical absorption modifiers. The relationships between the lipophilicity/polarity and the chemical structure of the studied compounds as well as the relationships between their chemical structure and penetration enhancement effect are discussed in this article.

Remotely controlled diffusion from magnetic liposome microgels.

The reversible, temperature-dependent change in the permeability of a phospholipid bilayer has been used for controlling the diffusion rate of encapsulated molecular payload from liposomes. Liposomes were preloaded with a fluorescent dye and immobilized in calcium alginate hydrogel microparticles that also contained iron oxide nanoparticles. The composite microparticles were produced by a drop-on-demand inkjet method. The ability of iron oxide nanoparticles to locally dissipate heat upon exposure to a radio-frequency (RF) alternating magnetic field was used to control the local temperature and therefore diffusion from the liposomes in a contactless way using an RF coil. Several different release patterns were realized, including repeated on-demand release. The internal structure of the composite alginate-liposome-magnetite microparticles was investigated, and the influence of microparticle concentration on the heating rate was determined. In order to achieve a temperature rise required for the liposome membrane melting, the concentration of alginate beads should be at least 25% of their maximum packing density for the nanoparticle concentration and specific absorption rate used.

Designing a dynamic dissolution method: a review of instrumental options and corresponding physiology of stomach and small intestine.

Development of new pharmaceutical compounds and dosage forms often requires in vitro dissolution testing with the closest similarity to the human gastrointestinal (GI) tract. To create such conditions, one needs a suitable dissolution apparatus and the appropriate data on the human GI physiology. This review discusses technological approaches applicable in biorelevant dissolutions as well as the physiology of stomach and small intestine in both fasted and fed state, that is, volumes of contents, transit times for water/food and various solid oral dosage forms, pH, osmolality, surface tension, buffer capacity, and concentrations of bile salts, phospholipids, enzymes, and Ca(2+) ions. The information is aimed to provide clear suggestions on how these conditions should be set in a dynamic biorelevant dissolution test.

New propanoyloxy derivatives of 5ß-cholan-24-oic acid as drug absorption modifiers.

A series of final twelve propanoyloxy derivatives of 5ß-cholan-24-oic acid (O-propanoyl derivatives of cholic acid) as potential drug absorption modifiers (skin penetration enhancers, intestinal absorption promoters) was generated by multistep synthesis. Structure confirmation of all generated compounds was accomplished by 1H NMR, 13C NMR, IR and MS spectroscopy methods. All the prepared compounds were analyzed using RP-TLC, and their lipophilicity (RM) was determined. The hydrophobicity (log P), solubility (log S), polar surface area (PSA) and molar volume (MV) of the studied compounds were also calculated. All the target compounds were tested for their in vitro transdermal penetration effect and as potential intestinal absorption enhancers. The cytotoxicity of all the evaluated compounds was evaluated against normal human skin fibroblast cells. Their anti-proliferative activity was also assessed against human cancer cell lines: T-lymphoblastic leukemia cell line and breast adenocarcinoma cell line. One compound showed selective cytotoxicity against human skin fibroblast cells and another compound possessed the highest cytotoxicity against all the tested cell lines. Only one compound expressed anti-proliferative effect on leukemia cancer cells without affecting the growth of normal cells, which should be promising in potential development of new drugs. Most of the target compounds showed minimal anti-proliferative activity (IC50>37 µM), indicating they would have moderate cytotoxicity when administered as chemical absorption modifiers. The relationships between the lipophilicity/polarity and the chemical structure of the studied compounds as well as the relationships between their chemical structure and enhancement effect are discussed in this article.

Encapsulation stability and temperature-dependent release kinetics from hydrogel-immobilised liposomes.

Composite microparticles consisting of a calcium alginate gel matrix with embedded liposomes made from cholesterol:DPPC (dipalmitoylphosphatidylcholine) mixtures were considered. Factors affecting the encapsulation stability of liposomes during the gel formation by ionic cross-linking--namely temperature and the cholesterol:DPPC ratio--were systematically investigated. The liposomes were found to be tolerant to Ca(2+) ions during cross-linking of the gel and stable in the hydrogel matrix for extended periods of time when cholesterol was present in the phospholipid bilayer and temperature was kept sufficiently below the phase transition. The temperature-controlled release rate of encapsulated fluorescent dye was quantified. It is shown that a defined quantity of encapsulated substance can be repeatedly released from the embedded liposomes "on-demand" by short temperature pulses of suitably chosen duration and amplitude. This makes the hydrogel-liposome composites potential candidates for applications such as controlled drug delivery or study of reaction-diffusion phenomena in compartmentalised systems.

In vitro permeation of micronized and nanonized alaptide from semisolid formulations.

This study is focused on in vitro permeation of the original Czech compound, a skin/mucosa tissue regeneration promoter, known under the international nonproprietary name "alaptide," in micronized and nanonized forms. Alaptide showed a great potential for local applications for treatment and/or regeneration of the injured skin. The above mentioned technological modifications influence the permeation of alaptide through artificial or biological membranes, such as PAMPA or skin. The permeation of micronized and nanonized form of alaptide formulated to various semisolid pharmaceutical compositions through full-thickness pig ear skin using a Franz cell has been investigated in detail. In general, it can be concluded that the nanonized alaptide permeated through the skin less than the micronized form; different observations were made for permeation through the PAMPA system, where the micronized form showed lower permeation than the nanonized alaptide.

Preparation of candesartan and atorvastatin nanoparticles by solvent evaporation.

The solubility, absorption and distribution of a drug are involved in the basic aspects of oral bioavailability Solubility is an essential characteristic and influences the efficiency of the drug. Over the last ten years, the number of poorly soluble drugs has steadily increased. One of the progressive ways for increasing oral bioavaibility is the technique of nanoparticle preparation, which allows many drugs to thus reach the intended site of action. Candesartan cilexetil and atorvastatin, belonging to class II of the biopharmaceutical classification system, were chosen as model active pharmaceutical ingredients in this study. Forty samples were prepared either by antisolvent precipitation/solvent evaporation method or by the emulsion/solvent evaporation technique with various commonly used surface-active excipients as nanoparticle stabilizers. All samples were analyzed by means of dynamic light scattering. The particle size of the determined 36 nanoparticle samples was to 574 nm, whereas 32 samples contained nanoparticles of less than 200 nm. Relationships between solvents and excipients used and their amount are discussed. Based on the results the investigated solvent evaporation methods can be used as an effective and an affordable technique for the preparation of nanoparticles.

Primary investigation of the preparation of nanoparticles by precipitation.

The absorption, distribution, biotransformation and excretion of a drug involve its transport across cell membranes. This process is essential and influenced by the characteristics of the drug, especially its molecular size and shape, solubility at the site of its absorption, relative lipid solubility, etc. One of the progressive ways for increasing bioavaibility is a nanoparticle preparation technique. Cholesterol, cholestenolone and pregnenolone acetate as model active pharmaceutical ingredients and some of the commonly used excipients as nanoparticle stabilizers were used in the investigated precipitation method that was modified and simplified and can be used as an effective and an affordable technique for the preparation of nanoparticles. All 120 prepared samples were analyzed by means of dynamic light scattering (Nanophox). The range of the particle size of the determined 100 nanoparticle samples was from 1 nm to 773 nm, whereas 82 samples contained nanoparticles of less than 200 nm. Relationships between solvents and used excipients and their amount are discussed.

Investigation of new acyloxy derivatives of cholic acid and their esters as drug absorption modifiers.

Skin penetration enhancers are used in the formulation of transdermal delivery systems for drugs that are otherwise not sufficiently skin-permeable. Intestinal absorption promoters/enhancers are used as excipients in oral formulations of poorly oral-bioavailable drugs. Series of fourteen acyloxy derivatives of 5ß-cholic acid as potential drug absorption modifiers was generated by multistep synthesis. The synthesis of all newly prepared compounds is presented here. Structure confirmation of all generated compounds was accomplished by (1)H NMR, (13)C NMR, IR and MS spectroscopy methods. All the prepared compounds were analyzed using RP-TLC, and their lipophilicity (R(M)) was determined. The hydrophobicity (logP) and solubility (logS) of the studied compounds were also calculated using two commercially available programs. All the target compounds were tested for their in vitro transdermal penetration activity and as potential intestinal absorption enhancers. The anti-proliferative activity of all the final compounds was also assessed against the human cancer cell lines: T-lymphoblastic leukemia cell line and the breast adenocarcinoma cell line. Their cytotoxicity was also evaluated against the normal human skin fibroblast cells. Two compounds showed anti-proliferative effect on cancer cells without affecting the growth of normal cells, which should be promising in potential development of new drugs. Most of the target compounds showed minimal anti-proliferative activity (IC(50)>37 µM), indicating they would have low cytotoxicity when administered as chemical absorption modifiers. The relationships between the lipophilicity and the chemical structure of the studied compounds as well as the relationships between their chemical structure and enhancement effects are discussed in this article.

Crystallization products of risedronate with carbohydrates and their substituted derivatives.

The gastrointestinal absorption of bisphosphonates is in general only about 1%. To address this problem mixtures of risedronate monosodium salt with twelve varied sugar alcohols, furanoses, pyranoses and eight gluco-, manno- and galactopyranoside derivatives as counterions were designed in an effort to prepare co-crystals/new entities with improved intestinal absorption. Crystalline forms were generated by means of kinetically and/or thermodynamically controlled crystallization processes. One hundred and fifty-two prepared samples were screened by means of FT-NIR and FT-Raman spectroscopy. No co-crystal was prepared, but noteworthy results were obtained. A new solid phase of risedronate monosodium salt generated in the presence of phenyl-ß-d-galactopyranoside under thermodynamically controlled crystallization conditions was found and also characterized using solid state NMR spectroscopy, X-ray powder diffraction and differential scanning calorimetry. This new polymorph was named as form P. Interactions between risedronate monosodium salt and both carbohydrates were confirmed by means of molecular dynamics simulation. In the present study the relationships between the chemical structures of the studied compounds required for crystalline form change are discussed.

Synthesis, antimycobacterial, antifungal and photosynthesis-inhibiting activity of chlorinated N-phenylpyrazine-2-carboxamides.

A series of sixteen pyrazinamide analogues with the -CONH- linker connecting the pyrazine and benzene rings was synthesized by the condensation of chlorides of substituted pyrazinecarboxylic acids with ring-substituted (chlorine) anilines. The prepared compounds were characterized and evaluated for their antimycobacterial and antifungal activity, and for their ability to inhibit photosynthetic electron transport (PET). 6-Chloro-N-(4-chlorophenyl)pyrazine-2-carboxamide manifested the highest activity against Mycobacterium tuberculosis strain H37Rv (65% inhibition at 6.25 µg/mL). The highest antifungal effect against Trichophyton mentagrophytes, the most susceptible fungal strain tested, was found for 6-chloro-5-tert-butyl-N-(3,4-dichlorophenyl)pyrazine-2-carboxamide (MIC=62.5 µmol/L). 6-chloro-5-tert-butyl-N-(4-chlorophenyl)pyrazine-2-carboxamide showed the highest PET inhibition in spinach chloroplasts (Spinacia oleracea L.) chloroplasts (IC50=43.0 µmol/L). For all the compounds, the relationships between the lipophilicity and the chemical structure of the studied compounds as well as their structure-activity relationships are discussed.

Preparation and properties of new co-crystals of ibandronate with gluco- or galactopyranoside derivatives.

Mixtures of ibandronate monosodium salt with eleven gluco- and/or galacto-pyranoside derivatives as counterions were designed to prepare co-crystals with improved intestinal absorption. In general, gastrointestinal absorption of bisphosphonates after oral administration is approximately 1%. Co-crystals were generated by means of thermodynamically and/or kinetically controlled crystallization processes. Seventy-seven prepared samples were analyzed by means of FT-NIR, FT-Raman spectrometry and solid state NMR spectroscopy. New entities of ibandronate monosodium salt with phenyl-ß-D-galactopyranoside were found and characterized. The absorption of these potential new co-crystals was investigated by means of PAMPA experiments. In the present study the relationships between the chemical structures of the studied compounds required for co-crystal generation are discussed.

Product of alaptide synthesis: determination of the absolute configuration.

Alaptide is the active substance of the veterinary dermatological ointment ALAPTID and a potential drug in human medicine. Electronic circular dichroism spectroscopy (ECD), transparent spectral region optical rotation (OR), and ab initio calculations were employed to determine the absolute configuration of alaptide. No X-ray structural data determining the absolute configuration were available. It was not possible to employ vibrational circular dichroism spectroscopy (VCD), because alaptide was not sufficiently soluble in common solvents used in VCD spectroscopy to generate reliable spectra. Both ECD spectra and OR values of alaptide solution were in good agreement with predicted data and determined unambiguously the absolute configuration of alaptide synthesized from (S)-alanine as being (S).

Rhodanineacetic acid derivatives as potential drugs: preparation, hydrophobic properties and antifungal activity of (5-arylalkylidene-4-oxo-2-thioxo-1,3-thiazolidin-3-yl)acetic acids.

Some [(5Z)-(5-arylalkylidene-4-oxo-2-thioxo-1,3-thiazolidin-3-yl)]acetic acids were prepared as potential antifungal compounds. The general synthetic approach to all synthesized compounds is presented. Lipophilicity of all the discussed rhodanine-3-acetic acid derivatives was analyzed using a reversed phase high performance liquid chromatography (RP-HPLC) method. The procedure was performed under isocratic conditions with methanol as an organic modifier in the mobile phase using an end-capped non-polar C(18) stationary RP column. The RP-HPLC retention parameter log k (the logarithm of the capacity factor k) is compared with log P values calculated in silico. All compounds were evaluated for antifungal effects against selected fungal species. Most compounds exhibited no interesting activity, and only {(5Z)-[4-oxo-5-(pyridin-2- ylmethylidene)-2-thioxo-1,3-thiazolidin-3-yl]}acetic acid strongly inhibited the growth of Candida tropicalis 156, Candida krusei E 28, Candida glabrata 20/I and Trichosporon asahii 1188.

Investigating biological activity spectrum for novel styrylquinazoline analogues.

In this study, series of ring-substituted 2-styrylquinazolin-4(3H)-one and 4-chloro-2-styrylquinazoline derivatives were prepared. The syntheses of the discussed compounds are presented. The compounds were analyzed by RP-HPLC to determine lipophilicity. They were tested for their inhibitory activity on photosynthetic electron transport (PET) in spinach (Spinacia oleracea L.) chloroplasts. Primary in vitro screening of the synthesized compounds was also performed against four mycobacterial strains and against eight fungal strains. Several compounds showed biological activity comparable with or higher than that of the standard isoniazid. It was found that the electronic properties of the R substituent, and not the total lipophilicity of the compound, were decisive for the photosynthesis-inhibiting activity of tested compounds.