Preparation and evaluation of release characteristics of 3TabGum, a novel chewing device

A new chewing gum device in the form of a three layers tablet (3TabGum) has been developed. The new drug delivery system is obtained, at room temperature, by direct compression using conventional pharmaceutical equipment. Basically, the resulting chewing gum tablets comprise a gum core combined with two protective antiadherent external layers, which prevent gum adhesion to the punches of the tableting machine. Drug release from a dosage form is the critical step in drug absorption and bioavailability, thus an experimental protocol has been designed to evaluate the efficiency of this kind of therapeutic system by verifying its capability to release the drug dose and by assessing the delivery rate. Simple diffusion into the medium causes the release of only a small percentage of the drug contained in the medicated chewing gum, while the delivery of the major part of the dose occurs during mastication. The results obtained in this study suggest that water soluble drugs are freely and easily released by chewing gums, while for actives characterized by reduced water solubility the release rate depends on the chewing time although all the drugs tested are completely released after a reasonable mastication time.

Polymers-gamma ray interaction. Effects of gamma irradiation on modified release drug delivery systems for oral administration

The aim of this work is to verify the efficiency of two kinds of matrix tablets formulations containing PEO or PVA as retarding polymer. Moreover, since in the last years the exposure to ionizing radiation is a more and more used method to reduce bacterial charge in pharmaceutical products, the effects of gamma irradiation on these two kinds of polymers has been evaluated. The study is performed on matrix tablets containing diltiazem HCl, as model drug, and polyethylene oxides (PEO) of two different molecular weights or polyvinylalchool (PVA) of medium degree of hydrolysis, as drug release modulators. Dissolution of the matrices, release of diltiazem and morphological behaviour of the samples, before and after exposure to increasing doses of gamma irradiation, are investigated in order to verify their stability. The results show that the ionizing radiation does not modify significantly the dissolution trend of the PVA samples; on the contrary, the dissolution and the morphological behaviour of the PEO matrices is strongly affected by the radiation dose received. In particular, the dissolution rate of the irradiated PEO tablets dramatically increases as a function of the irradiation dose and the swelling process, which characterised the non-irradiated PEO samples, was replaced by a rapid erosion process responsible for the quickly dissolution of the matrices. The changes of the dissolution and morphological PEO tablets performances could be explained by a breaking of the polymeric chains (shown by EPR studies) as a consequence of the exposure to gamma rays. These chemical-structural modifications of the polymers are responsible for the reduced efficacy of the PEO systems in controlling the drug release rate.

Characterization and selection of vaginal Lactobacillus strains for the preparation of vaginal tablets

AIMS

To characterize and select Lactobacillus strains for properties that would make them a good alternative to the use of antibiotics to treat human vaginal infections.

METHODS AND RESULTS

Ten Lactobacillus strains belonging to four different Lactobacillus species were analysed for properties relating to mucosal colonization or microbial antagonism (adhesion to human epithelial cells, hydrogen peroxide production, antimicrobial activity towards Gardnerella vaginalis and Candida albicans and coaggregation with pathogens). The involvement of electrostatic interactions and the influence of bacterial metabolic state in the binding of lactobacilli to the cell surface were also studied. Adherence to epithelial cells varied greatly among the Lactobacillus species and among different strains belonging to the same Lactobacillus species. The reduction in surface negative electric charge promoted the binding of several Lactobacillus strains to the cell membrane whereas lyophilization reduced the adhesion capacity of many isolates. The antimicrobial activity of lactobacilli culture supernatant fluids was not directly related to the production of H2O2.

CONCLUSIONS

Three strains (Lactobacillus brevis CD2, Lact. salivarius FV2 and Lact. gasseri MB335) showed optimal properties and were, therefore, selected for the preparation of vaginal tablets. The selected strains adhered to epithelial cells displacing vaginal pathogens; they produced high levels of H2O2, coaggregated with pathogens and inhibited the growth of G. vaginalis.

SIGNIFICANCE AND IMPACT OF THE STUDY

The dosage formulation developed in this study appears to be a good candidate for the probiotic prophylaxis and treatment of human vaginal infections.

Chemical and physical stability of hydroxypropylmethylcellulose matrices containing diltiazem hydrochloride after gamma irradiation

In recent years, the exposure to gamma-radiation is an increasingly used method to sterilize or to reduce bacterial charge in drug-delivery devices. The aim of this study was to investigate whether the ionizing radiation may be responsible for drug inactivation or for the alteration of the functional excipient used to modulate drug release from a controlled-release delivery system. In this work, we investigated the physical and dissolution stability of prolonged release matrix tablets containing diltiazem hydrochloride, as a model drug, and hydroxypropylmethylcellulose (HPMC) of two different viscosity grades, as the retarding polymer, before and after exposure to increasing doses of gamma-rays. The results show that gamma-irradiation induces chemical modifications in the structure of the active agent, and also of the hydrophilic polymer. The electronic paramagnetic resonance analysis of gamma-irradiated diltiazem has afforded evidence of carbon radicals stemming from C-H bond ruptures and sulphur radicals, the latter being formed mainly after admission of air at room temperature. The major radical products in the HPMC polymer radiolysis have been reckoned with chain scission events in agreement with the results of viscosity measurements that show a progressive decrease of the average molecular weight with increasing the radiation dose. The elaboration of the viscosity data has led to linear relationships between the eta(o)/eta ratio and the radiation dose D which were rationalized with the following equation under the assumption of a Mark-Houwink Sakurada coefficient a approximately equal 1: eta(o)/eta = (1 + uy(o) D)(a). In this equation, D is gamma-radiation dose, eta(o) and eta are the reduced viscosities before and after the irradiation respectively, u is the number average degree of polymerization, and y(o) is the chain scission radiolytic yield. From the linear relationships G(chain scissions) = 1.2 x 10(-6) and 1.4 x 10(-6) moles/J have been obtained for the two HPMC polymer samples M100 and M4 of different molecular weight used in the experiments. These changes could be responsible for the alteration of the drug-release mechanism and reduced polymer efficacy in controlling drug release.

Photostability of extended-release matrix formulations

The photostability of drugs has been widely studied while less attention is devoted to the possible modifications that UV light may induce on the excipients of a dosage form, in particular, on the functional polymers used to modulate drug delivery. In this work we have evaluated the effect of UV light on the release characteristics of extended-release matrix tablets containing hydroxypropylmethylcellulose (HPMC) or polyethylene oxide (PEO) as retarding polymers. Two different model drugs have been used: nifedipine (insoluble and photolabile drug) and diltiazem (soluble and photostable drug). Photodecomposition of nifedipine was evaluated and the formation of the photoproducts was followed during the dissolution process. Regarding the dissolution stability, the matrix tablets containing HPMC exposed to UV light have not shown significant differences in drug release profiles compared to the same non-irradiated formulation, while the matrix tablets containing PEO and exposed to the same conditions of UV light have shown a remarkable increase of drug release rate within the first minutes of the dissolution test (burst effect) which is particularly critical because it can cause the loss of the desired therapeutic control.

Boar semen controlled delivery system: storage and in vitro spermatozoa release

Swine spermatozoa were encapsulated in barium alginate and protamine-barium alginate membranes to lengthen their preservation time and to provide a means of controlling their release. Precocious acrosome reactions and secondary anomalies were measured as indices of semen quality. These characteristics were observed for two forms of encapsulated spermatozoa when stored at 18 and 38 degrees C for 24 h and for semen diluted in a classical extender at both temperatures. The results indicate that encapsulation enhances semen preservation, providing protection against membrane damage upon dilution. The effect is even more evident at the higher temperature (38 degrees C), where cell metabolism is higher. An in vitro release test of spermatozoa showed a massive cell delivery from barium alginate capsules within 6 h, and a slow release from protamine-barium alginate capsules. The properties of spermatozoa 24 h after release did not differ from the semen stored at the same temperature in capsules, indicating that the release process does not impair semen quality.

Boar semen controlled delivery system: analysis of batch seasonal variability

A new encapsulation technology of swine semen is proposed to improve the quality of stored spermatozoa and to obtain the controlled release of viable cells, reducing the number of instrumental inseminations. This technology has been employed to produce barium alginate gel capsules in different seasons; an analysis of batch reproducibility was performed, and total capsule diameter, gel thickness and weight of capsules were determined as indices of batch properties. A seasonal variability was found but each batch was substantially homogeneous. The variability could be related to the biological variability of the semen employed as raw material as well as to the technological process.

Barium alginate cell-delivery systems: correlation between technological parameters

The most recent trends for the development of several in vitro cell cultures have been oriented towards the cell immobilisation in 3-dimensional scaffolds and cell encapsulation. In fact, an important requirement of cell survival is self-assembly in functional communities, in the presence of an artificial extracellular matrix. In our research, a previously described technique for spermatozoa encapsulation was applied to obtain capsules loaded with an opaque agent as a model, and to perform a formulative study. A process variable, barium ion concentration, was correlated to some capsule properties, such as weight, gel thickness, total and core diameter. Ion concentration can be modified to obtain capsules with predictable characteristics.

Dissolution behaviour of hydrophilic matrix tablets containing two different polyethylene oxides (PEOs) for the controlled release of a water-soluble drug. Dimensionality study

Hydrophilic matrix tablets containing polyethylene oxides as the retarding polymer have been successfully employed in the controlled release of drugs. To evaluate the relative influence of drug diffusion and polymer erosion mechanisms in the drug delivery process, we studied the hydration behaviour of matrix tablets containing a water-soluble drug and PEOs of two different molecular weights: Polyox WSRN 1105 (Mw = 0.9 x 10(6)) and Polyox WSRN 301 (Mw = 4 x 10(6)). The hydration rate, the extent of swelling, and the erosion rate of matrices containing the polymer, the drug and tableting excipients were evaluated in comparison to tablets made of pure polymer. The results of these studies on function of the release behaviour were then discussed. The results show that the higher molecular weight PEO swells to a greater extent and tends to form, upon hydration, a stronger gel, which is therefore less liable to erosion, if compared to the lower molecular weight PEO. This difference in the erosion behaviour can explain the different efficiencies of the two polymeric products in modulating the delivery rate of the water-soluble drug. Moreover, the presence of other soluble components (drug and excipients) in the dosage form enhances the erosion trend of the tablets with a consequent reduction of the efficiency of the polymer in drug release control.

Regulation of GABA release by nicotinic acetylcholine receptors in the neonatal rat hippocampus

1. The whole-cell configuration of the patch-clamp technique was used to study the modulation of giant depolarizing potentials (GDPs) by nicotinic acetylcholine receptors (nAChRs) in CA3 hippocampal neurons in slices from postnatal day (P) 2-6 rats. 2. Bath application of nicotine increased GDP frequency in a concentration-dependent manner. For example, nicotine (0.5-1 microM) enhanced GDP frequency from 0.05 +/- 0.04 to 0.17 +/- 0.04 Hz. This effect was prevented by the broad-spectrum nicotinic receptor antagonist dihydro-beta-erythtroidine (DHbetaE, 50 microM) and partially antagonized by methyllycaconitine (MLA, 50 nM) a competitive antagonist of alpha7 nAChRs. GDP frequency was also enhanced by AR-17779 (100 microM), a selective agonist of alpha7 nAChRs. 3. The GABA(A) receptor antagonist bicuculline (10 microM) and the non-NMDA glutamate receptor antagonist DNQX (20 microM) blocked GDPs and prevented the effects of nicotine on GDPs. In the presence of DNQX, nicotine increased GABA-mediated synaptic noise, indicating that this drug may have a direct effect on GABAergic interneurons. 4. Bath application of edrophonium (20 microM), a cholinesterase inhibitor, in the presence of atropine (1 microM), increased GDP frequency, indicating that nAChRs can be activated by ACh released from the septo-hippocampal fibres. This effect was prevented by DHbetaE (50 microM). 5. In the majority of neurons tested, MLA (50 nM) and DHbetaE (50 microM) reduced the frequency of GDPs with different efficacy: a reduction of 98 +/- 11 and 61 +/- 29 % was observed with DHbetaE and MLA, respectively. In a subset of cells (40 % in the case of MLA and 17 % in the case of DHbetaE) these drugs induced a twofold increase in GDP frequency. 6. It is suggested that, during development, nAChRs modulate the release of GABA, assessed as GDPs, through distinct nAChRs. The rise of intracellular calcium via nAChRs would further strengthen GABA-mediated oscillatory activity. This can be crucial for consolidation of synaptic contacts and for the fine-tuning of the developing hippocampus.

Determination of 226Ra in biological samples by adsorption on specific adsorbers

The determination of 226Ra in biological samples, such as milk and grass, was studied. 226Ra analysis of cow's milk was studied starting from de-fatted milk. The proteins were eliminated by coagulation of the colloidal phase with trichloroacetic acid. Phosphorus was then removed by precipitating it as molybdophosphate and finally adsorption was carried out by using two different adsorbers in order to concentrate and purify radium. Lead rhodizonate (LEHRO) adsorbed on charcoal and partially reduced tin dioxide (PRTD) were utilised. A method for the determination of 226Ra in grass ashes was also investigated. The main interference, due to magnesium, hinders the use of LERHO, so the proposed procedure is based on adsorption of radium on PRTD at pH 9.5. The magnesium concentration was depleted by precipitating barium (carrier) and radium with calcium carbonate at pH 8 before the adsorption step. The high phosphorus concentration in grass also interferes in the determination of 226Ra; phosphorus was eliminated as above via molybdophosphate precipitation. The radium was carried by barium and spiked with 133Ba. The yield of the chemical procedure was evaluated on the basis of 133Ba activity. Radium samples were alpha-counted and the activity was evaluated with a suitable calibration curve. Both exchangers in the milk analysis and PRTD in grass analysis were shown to be helpful in order to set up an easily performed procedure, which allows many samples to be processed simultaneously. All the methods adopted were shown to be very sensitive. Under the experimental conditions used, with 1 L of milk or 5 g of grass ashes, the limit was about 3 mBq 226Ra L-1 milk and < 1 mBq 226Ra g-1 grass ashes.

Technological and biological evaluation of tablets containing different strains of lactobacilli for vaginal administration

Ten strains of lactobacilli were evaluated for the administration of viable microorganisms to restore the normal indigenous flora in the treatment of urogenital tract infections (UTI) in women. As the strains considered are facultative anaerobes, optimization of the production process was particularly critical to preserve bacterial viability. The microorganisms were formulated in single- and double-layer vaginal tablets. The two layers were characterized by different release properties: one is an effervescent composition that ensures a rapid and complete distribution of the active ingredient over the whole vaginal surface; while the second is a sustained release composition capable of releasing the lactobacilli over a longer period of time. Three different retarding polymers were tested, and all the formulations and tablets were evaluated in terms of technological processability, bacterial viability and stability, and cell adhesion properties of the microorganisms. From the results obtained, three out of ten strains appear particularly suitable for their application in the treatment of UTI. A larger batch of tablets made with a mixture of the three strains was then evaluated, confirming the feasibility of their industrial production and a good bacterial viability in the final dosage form.

Effect of drying methods on retention of moist sucralfate gel properties

The aim of this work was to find a drying procedure for moist sucralfate gel capable of producing dried sucralfate gel that retains the original gel properties of bioadhesion, rheology, and micromeritics. Spray-drying and microwave-drying procedures were employed. Mannitol was used as a gel-protective substance during the drying processes. The spray drying of moist sucralfate gel gave rise to a powder whose water suspensions showed significantly reduced viscosity. The bioadhesion of spray-dried sucralfate gel was strongly reduced by drying. When mannitol was used as a gel protector, the spray-dried sucralfate in part maintained the original bioadhesion of moist sucralfate gel. The preparation of a dried sucralfate gel retaining the bioadhesion characteristics, avoiding the use of mannitol, was made possible using the microwave-drying procedure. The microwave-dried product possesses a granular morphology suitable for direct compression because it is a free flowing and strongly coherent granular powder.

Disintegration propensity of tablets evaluated by means of disintegrating force kinetics

The aim of this work was to measure the disintegrating force concomitantly with tablet disintegration, in order to evaluate the disintegration propensity of tablets. Disintegration and dissolution were measured on tablets containing two poorly soluble drugs (diclofenac sodium or ketoprofen), including different percentages of two disintegrants (Explotab or Ac-Di-Sol). Because of the experimental setup, the disintegrating force measured was the result of the force generated by disintegrant swelling and dissipated by tablet disintegration. The disintegrating force versus time curves had shapes ranging from a skewed distribution curve to a bell-shaped curve, depending on slow or rapid disintegration of tablets, respectively. Interestingly, the shape of the resulting curves was very sensitive to the composition of the tablet. When the disintegrant in the formula was increased, the force-time curve approached the bell-like shape. The disintegration propensity of the tablet can be evaluated by the disintegrating force development during disintegration. The disintegration improvement of the formula can be predicted. The disintegrating force curve allows for the clear identification of the optimal percentage of disintegrant to be used.

SDF-1alpha-mediated modulation of synaptic transmission in rat cerebellum

The functional expression of the seven-transmembrane domain G protein-coupled chemokine receptor CXCR-4/fusin in rat nerve cell was demonstrated by staining with a polyclonal anti-CXCR-4 Ab, and by evaluating the calcium responses to the physiological agonist stromal-derived cell factor-1alpha (SDF-1alpha) in both cerebellar granule cells in culture and Purkinje neurons (PNs) in cerebellar slices. Cerebellar glial, granule and Purkinje cells showed a pronounced staining for CXCR-4. Furthermore, cultured granule cells exhibited Ca2+ transients elicited by the application of SDF-1alpha, both in cell bodies and in neuronal processes. Whole-cell patch-clamped PNs in cerebellar slices responded to SDF-1alpha application by a slow inward current followed by an increase of both intracellular Ca2+ level and spontaneous synaptic activity. In particular, the SDF-1alpha-induced slow inward current was considerably reduced by ionotropic glutamate receptor blockers, but developed fully in a medium in which synaptic transmission was inhibited, indicating that this current might be, at least in part, mediated by extrasynaptic glutamate, possibly released from the surrounding glial and/or nerve cells. Taken together, these findings indicate a functional involvement of CXCR-4 in the modulation of synaptic transmission, adding another member to the repertoire of the chemokine receptors exerting a neuromodulatory role in the cerebellum.

Controlled release of swine semen encapsulated in calcium alginate beads

A quick and successful encapsulation method of swine spermatozoa is described: hydroxypropylmethylcellulose and calcium chloride were added to the sampled ejaculate swine sperm (sperm-rich fraction: creamy white) and then this suspension was dropped into an aqueous solution of sodium alginate. In order to obtain different capsule thicknesses, different calcium chloride concentrations were used. The influence of different formulations on in vitro spermatozoa release behavior and on the mechanical properties has been studied. In vitro sperm kinetics (motility and average velocity) have been determined. The results obtained from motility and average velocity tests of treated seminal material are promising, especially if the difficulty of preservation of swine spermatozoa compared to bovine sperm is considered. The different membranes obtained from the different calcium concentrations have had an influence on mechanical properties and on the release profile of spermatozoa from the capsules, and therefore, it is possible to modulate the release rate of the cells.

High molecular weight polyethylene oxides (PEOs) as an alternative to HPMC in controlled release dosage forms

High molecular weight polyethylene oxides (PEOs) have recently been proposed as an alternative to hydroxypropylmethylcellulose (HPMC) in controlled release matrix tablets. In this study, we compared the performance of PEO and HPMC polymers when employed in the Geomatrix technology, a versatile, well-known method to achieve extended release of drugs at a constant rate. Four core formulations were prepared, containing a soluble drug (diltiazem) and, alternatively, PEO or HPMC of two different viscosity grades. These formulations have the same composition except for the polymer employed. Similarly, four barrier formulations were also prepared, which only differ in the kind of polymer employed. Three-layer Geomatrix systems were then prepared using these core and barrier formulations. The release profiles of the different three-layer systems obtained were compared, to verify if PEO could efficiently replace HPMC in this type of dosage form. The results show that slower release rates can be obtained from the plain matrices containing HPMC compared to PEO, moreover HPMC, used in the barrier formulations, is generally more efficient in controlling drug release rate in three-layer Geomatrix systems.