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Biomedical subjects

J Joachim

Publications and source records attributed to J Joachim.

At least 19 recordsLinked to original sources
PubMed2001

In-vitro comparative study of buccal mucoadhesive performance of different polymeric films.

A comparison of the buccal mucoadhesive performance of different polymeric films was carried out using texture analyzer TA-XT2i. A large range of putative polymers differing in their chemical nature, molecular structure as well as hydration status was used. The used polymeric films were classified in rank order of buccal mucoadhesive performance, namely carbopol 971P>polycarbophil>Carrrageenan type lambda > Sodium carboxymethylcellulose. Swelling state as well as tensile strength of the used polymeric films was used as measuring parameters of mucoadhesive interaction. These two approaches gave two opposite orders of performance between CMC and Carrrageenan type lambda after a contact time of 15 min. However the measurement of the viscoelastic moduli of the hydrogels gave the same ranking order of mucoadhesive performance after the same contact time. In reference to the previous works, we noted the importance of the molecular weight, the density of charges, the composition of which the chains of molecules are capable to arrange themselves in a network like form, thus those which are characterized by a tan delta<1 (i.e network formation), are those which develop the best synergism with the mucus because of the reinforcement of an established link. The goal of this study is to assess the buccal mucoadhesive performance aiming to optimize the design of drug delivery via buccal mucoadhesive polymeric films

Adhesiveness↗
PubMed2001

Stress relaxation studies of granules as a function of different lubricants.

Viscoelastic properties of granules may be studied using stress relaxation. The effect of viscoelastic properties of different lubricants, namely magnesium stearate (Mgst), talc and precirol, on granule compaction properties was examined using texture analyzer TA-XT2i at low pressure. Normalized compact curves of stress relaxation have been discussed in relation to some parameters (flowability, porosity, viscoelasticity as well as particle size). The literature shows that viscoelasticity is always present and it produces an accompanying plastic deformation.This study revealed that bonding in compacted granules lubricated with Mgst was higher than those in compacts lubricated with the other two lubricants being studied. When studying the partial porosity of granule beds, we see that this is the result of stored energy, like the tablet case and the problem of its capping. The small stress relaxation due to talc or precirol suggested that these materials deformed principally by energy storage. However, a qualitative characterization of Mgst as tablet lubricant would be that it avoids the accumulation of stress in the compact that causes the problem of capping due to the entrapped air and therefore facilitates the optimization of pharmaceutical manufacturing. It has been possible to normalize stress relaxation using the Wischert model, represented by the sum of several exponentials, according to the nature of the lubricant. The use of texture analyzer TA-XT2i was considered to be a good technique for the evaluation of the stress relaxation of solid particles in the compression process at low pressure. It permitted the observation that viscoelasticity is influenced by the lubricant used. The brittle fracture index, like Carr's index values, has been correlated with the viscoelastic characteristics of granules.

Diglycerides↗
PubMed2000

Hot-melt coating technology. I. Influence of Compritol 888 Ato and granule size on theophylline release.

The aim of this work was to study the influence of theophylline granule size and the percentage of Compritol 888 Ato on in vitro drug release from granules and tablets. The granules were coated in a fluidized bed apparatus. The dissolution profiles of these granules differed from those of granules coated with classical agents, and there were also differences between the various sieve fractions studied. Drug release was characterized by a rapid-release phase, followed by a slow-release phase. Results indicate that theophylline release can be controlled by controlling granule size. Inspection of the appearance of the tablets at the end of the dissolution test revealed that all tablets containing Compritol 888 Ato remained intact. This indicated that the Compritol 888 Ato used in the tablet formulation created an inert matrix through which the drug diffused. It was found that the Higuchi relationship of linear square root of time was the best model to describe the release kinetics of the drug from tablets. This also confirmed that a matrix diffusion-controlled mechanism was operative. Given the difference between the dissolution profiles of the granules and the tablets, it was concluded that this matrix is formed during compression.

Bronchodilator Agents↗
PubMed2000

Hot melt coating technology: influence of Compritol 888 Ato and granule size on chloroquine release.

The tangential spray technique was used to coat chloroquine granules with Compritol 888 Ato in a fluidized bed (Glatt GPCG-1,1). After validation of the assay method for chloroquine, dissolution tests were carried out on four size fractions obtained from the same batch of granules. The dissolution profiles obtained showed differences in the rate of release between one fraction and another, despite the fact that each of these fractions had been coated with the same quantity of wax. This suggests that the rate of release of the chloroquine may be adjusted by controlling the size of the granules. Furthermore these dissolution profiles were characterized by a rapid release phase followed by a slow release phase. Examination of the surfaces of the granules from the various size fractions under a scanning electron microscope revealed that Compritol did not form a continuous film but existed rather as a lipid environment around the granule. This lipid environment was made up of solidified droplets of the wax which had become piled up on the surface of the granule. Compression of the granules produced tablets which remained intact until chloroquine dissolution was complete. This undicated that the active substance diffused across the Compritol matrix generated during compression. Determination of the dissolution kinetics using the Higuchi model demonstrated the diffusion release mechanism.

Amebicides↗
PubMed1999

Spectral acoustic structure of barking in roe deer (Capreolus capreolus). Sex-, age- and individual-related variations.

In roe deer, barking is a loud call commonly given by males and females during inter- or intraspecific interactions. The analysis of a set of 19 spectral variables computed on 560 calls revealed significant variation between sexes, individuals, and probably age classes. Discriminant analysis predicted the sex of an individual with a 93.5% probability from a small portion of the bark frequency range. Among six males, a linear combination of six variables predicted the identity of the barking individual with a 70% probability. These sexual and individual differences provide the potential for social recognition from vocalizations. These results are consistent with the hypothesis that barking in roe deer may allow remote signalling of presence, location and identity, and play an important role in the territorial system of this species.

Acoustics↗
PubMed1999

Compritol 888 ATO: an innovative hot-melt coating agent for prolonged-release drug formulations.

The aim of the present study was to assess the coating of drug-loaded sugar beads and lactose granules with Compritol 888 (National Formulary (NF)--Glyceryl Behenate). Theophylline was used as tracer and layered onto the beads, or granulated with lactose and sugar. Coating conditions (temperature, spray-rate, air pressure, etc.) were investigated for the production of prolonged release beads or granules, and dissolution kinetic curves were discussed. The study confirms the satisfactory coating potential of the hot-melt fluid-bed coating process on large spherules or granules. The optimized conditions confirm previous work, underscoring the considerable importance of the temperature of molten coating materials and the atomization air pressures. More sophisticated equipment would undoubtedly produce more efficient coating but the technique nevertheless seems promising. Practical data is now available for standard top spray equipment for fine and coarse granules. (1) Granule and spherule surface adhesion is controlled and consistent; (2) the coating is homogeneous, with continuous atomization and spraying onto the support; and (3) the release profile is directly related to the quantity of wax applied. Several competing mechanisms are also involved, including a diffusion-controlled process and a dissolution mechanism. Dissolution profiles appear to be consistent from one batch to another.

Air Pressure↗
PubMed1999

Controlled-release behavior of diphenhydramine hydrochloride loaded neutral microgranules and coated using ethylcellulose water dispersion.

The development of a loading method of a water-soluble drug using aqueous binding solution to produce microgranules that were then coated with an aqueous ethylcellulose dispersion to sustain drug release is described. The results, in terms of drug used, showed that besides the fluidized bed parameters, the amount of drug dissolved in the binder solution plays an important role in obtaining a satisfying result during the spraying process. Thus, it seems necessary to determine the critical concentration above which the material started to adhere to the interior of the fluidization column, and the possibility of drug layering onto carrier material is aggravated. ANOVA of the time parameter for release of 63.2% of total drug (td) value showed significant influence of ethylcellulose (Aquacoat ECD-30) and dibutyl sebacate concentration on diphenhydramine hydrochloride (DPH) release. The dissolution rate decreased with an increase in polymer concentration. The diffusional exponent n of the Peppas equation indicated that the DPH release kinetic was non-Fickian but approached Fickian diffusion, particularly at higher coating levels.

Cellulose↗
PubMed1999

Comparative tablet and rheological properties of new microcrystalline cellulose: direct compression and wet granulation methods.

The overall objective of this study was to compare the rheological properties and tablet characteristics of two new varieties of celluloses (Vivacel 101 and 102), recently produced and commercialized, with the classical varieties of celluloses (Avicel and Elcema). The results showed no significant differences in the rheological properties of Vivacel and Avicel, while significant differences were found between the two celluloses and Elcema. Furthermore, there were no statistically significant differences in the disintegration times and Td values of Vivacel and Avicel. In conclusion, it was found that these new celluloses offer all the known advantages of Avicel.

Cellulose↗
PubMed1994

Plasma concentrations after three different doses of topical isotretinoin.

The aim of the study was to investigate the plasma concentrations of isotretinoin and its metabolites, at three doses and after single and multiple topical applications of isotretinoin gel (0.05%) in hairless rats. We used a highly sensitive HPLC method for simultaneous determinations of these compounds, with a detection limit of 2 ng/ml in plasma. Isotretinoin and its metabolites were detected after single and multiple cutaneous applications of overdosing (2,000 mg) of isotretinoin gel up to 24 h after the single dose and after the last dose. The plasma concentrations of these compounds were below the limit of quantification in all the animals at all times for the 200- and 20-mg doses.

Administration, Topical↗
PubMed1991

[The homocysteinemia vascular risk factor. Methodologies and application to a clinical case].

Early onset vascular disease unexplained until today by usual risk factors (hyperlipidemia, hypertension, tobacco, stress), can now find an explanation in sulfur amino acid metabolism defect. By transsulfuration, alimentary methionine leads to homocysteine, which is itself turn into cysteine, or remethylated into methionine. Several abnormalities of these different pathways lead to plasma accumulation of homocysteine, which will be responsible of arterial or venous occlusive lesions, concerning peripheral or deep vessels. Homocysteine stays in plasma upon several forms: 75% being linked by disulfide bounds to proteins, 22% as disulfide, homocystine (homocysteine-homocysteine) or mixed-disulfide (homocysteine-cysteine), and less than 3% as free reduced homocysteine. Plasma reduction allows total homocysteine evaluation with amino acid autoanalyzer. The basal plasma homocysteine level is less than 14 microMl. However, levels near this basal value can be found in patients with latent abnormality, which needs to be revealed by a methionine loading test. This study concerns two methodologies and their application to the exploration of a patient with unidentified neurologic disorders. The first one describes a new galenic oral form of methionine. Other authors use the methionine load of 100 mg/kg dissolving it in a fruit juice glass. In order to obtain a complete dissolution of this weakly soluble substance and to ensure its total absorbtion by the patient, we prepare a granular form aimed to give in water a perfect flavoured suspension. The second methodology concerns methionine loading test and amino acid analysis. After 10 hours fasting, a 100 mg/kg peroral methionine load is realized performing 5 EDTA blood samples before and 4, 8, 12 and 24 hours after loading.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acids↗