Preparation and release characteristics of potassium chloride microcapsules

Starch-based materials for drug delivery in the gastrointestinal tract-A review

Starch is a natural copolymer with unique physicochemical characteristics. Historically, it has been physically, chemically, or enzymatically modified to obtain ad-hoc functional properties for its use in different applications. In this context, the use of starch-based materials in drug delivery systems (DDSs) has gained great attention mainly because it is cheap, biodegradable, biocompatible, and renewable. This paper reviews the state of the art in starch-based materials design for their use in drug-controlled release with internal stimulus responsiveness; i.e., pH, temperature, colonic microbiota, or enzymes; specifically, those orally administered for its release in the gastrointestinal tract (GIT). Physical-chemical principles in the design of these materials taking into account their response to a particular stimulus are discussed. The relationship between the type of DDSs structure, starch modification routes, and the corresponding drug release profiles are systematically analyzed. Furthermore, the challenges and prospects of starch-based materials for their use in stimulus-responsive DDSs are also debated.

Methoxybutropate microencapsulation by gelatin-acacia complex coacervation

Microcapsules of methoxybutropate solid particles or of an oily saturated solution of the same drug were prepared by complex coacervation between gelatin and acacia and dried with three different methods: isopropanol addition, spray-drying, and freeze-drying. Successively, microparticles were analyzed by infrared thermobalance, ultraviolet (UV) spectroscopy, optical and scanning electron microscopy, and sieves to find out parameters such as yield, moisture content, encapsulation percentage, morphology of solid particles, and particle size. Results highlighted that the most appropriate drying method for industrial purposes was spray-drying, particularly for oil-containing microcapsule formulations.

Drug delivery systems 5A. Oral drug delivery

The two main advantages of controlled drug delivery systems are: maintenance of therapeutically optimum drug concentrations in the plasma through zero-order release without significant fluctuations; and elimination of the need for frequent single dose administrations. The oral and other therapeutic systems in human use have validated the concept that controlled continuous drug release can minimize the daily dose of a drug required to maintain the required therapeutic effect, while minimizing unwanted pharmacological effects. By minimizing patient intervention, a design feature of therapeutic systems, compliance is automatically enhanced. Oral drug delivery systems, in particular, have required innovation in materials science to provide materials biocompatible during prolonged contact with body tissues, bioengineering to develop drug delivery modules, and clinical pharmacology for elucidation of drug action under conditions of continuous controlled drug administration. Recent work in advanced oral delivery has been primarily focused on liposome technology and the concept that substances that are normally destroyed by the stomach can be protected long enough before they could be absorbed downstream. For cost and patient convenience, oral delivery certainly would be an attractive method. The nature of biologic substances, however, with their unique technical problems, will probably limit greatly those that can be delivered orally. Besides, where delivery rate control is critical, oral delivery, even when possible, would probably be insufficiently precise. Oral delivery would also limit the substance to bloodstream delivery to the disease site. Even so, oral controlled drug delivery systems will likely find primary usefulness in specific carefully controlled therapies and prophylactic situations with due regard for drug interactions. This system represents a potentially very significant therapeutic modality. These delivery systems will find usefulness primarily in certain well-defined and well-controllable areas with due regard for individual patient variations. The purpose of the present article is to review oral controlled-release drug delivery systems, with particular emphasis on the practical aspects of testing and fabricating these systems and the underlying mechanisms by which control over drug release rate is accomplished.

Preparation of microspheres of water-soluble pharmaceuticals

An emulsion-solvent evaporation procedure involving the dispersion of an alcoholic solution of an active in liquid paraffin was used to prepare microspheres of water-soluble pharmaceuticals using ethylcellulose as a carrier. The effects of surfactant, plasticizer, drug loading, and agitation speed on drug release rate from the microspheres were evaluated. The release rates of water-soluble drugs from microspheres, ranging from 100 and 500 microns in diameter, were sustained over an extended time and were found to be related to the ratio of drug to polymer in the final product.

Effect of encapsulation of mefenamic acid with cationic Eudragit E on its bioavailability and gastric ulcerogenic activity in rabbits

Encapsulation of mefenamic acid (MFA), a potent non-steroidal anti-inflammatory drug with cationic acrylic resin, Eudragit E, was carried out using a fluidized-bed granulator (Glatt AG). Three drug:polymer ratios were prepared using 50 ml of 1, 2.5 and 5 per cent w/v aqueous suspension of Eudragit to coat 100 mg powdered drug. The bioavailability of the coated and uncoated drug was studied using four groups of animals, each consisting of six male rabbits (2-2.5 kg). Investigations were performed using the rabbits to examine the effects of prolonged administration of the coated and the uncoated MFA with Eudragit E(1 and 5 per cent) in a dose of 100 mg filled in hard gelatin capsules. One capsule was given daily for 30 days. Plasma levels of MFA with Eudragit E were significantly higher than those of drug only. Meanwhile, 5 per cent w/v polymer coating afforded higher drug availability than 2.5 per cent w/v which induced a higher level than 1 per cent w/v. Chronic gastric ulcers with different severities were found in the internal mucosa of all animals. In addition, there were multiple erosions in the glandular mucosa of stomachs of rabbits receiving MFA within the treatment period. IN the control group the gastric photograph was normal in every instance. Despite the extensive morphological damage at the end of treatment, the observed changes in the stomach of rabbits given coated drug is less deleterious than that treated with uncoated drug. The results of this study indicate that the coating of MFA with cationic Eudragit E increases its bioavailability and decreases the probability of ulceration.(ABSTRACT TRUNCATED AT 250 WORDS)

Dissolution studies of microencapsulated 4-sulphonamidophenoxyacetic acid: effect of preparative variables on dissolution

Ethylcellulose-walled microcapsules of 4-sulphonamidophenoxyacetic acid were prepared and their in vitro dissolution characteristics were investigated. Different release kinetics must be applied according to the respective average particle size and wall content values of the microcapsule fractions. The 'dissolution model' appears to fit better with small thin-walled microcapsules whereas, for larger thicker-walled microcapsules, Higuchi-type kinetics seem to describe the release of the major part of the drug more adequately.

Correlation of surface characteristics with ease of production and in vitro release of sodium salicylate from various enteric coated microcapsules prepared by pan coating

Nonpareil seeds were loaded with sodium salicylate and enteric coated with organic solvent based systems including polyvinyl acetate phthalate, cellacephate (CAP), shellac, hydroxypropylmethylcellulose phthalate, or Eudragit L as film former. Details of the pan coating procedure used were described. The CAP product showed optimum surface continuity when examined by scanning electron microscopy. The shellac product exhibited least aggregation during coating and consequently gave highest yields. Dissolution studies on the microcapsules in simulated gastric and intestinal media indicated that the CAP coated microcapsules had the most satisfactory enteric properties.

Particle size analysis of gelatin-acacia coacervate and ethylcellulose walled microcapsules

The Coulter counter has become one of the methods of choice for the measurement of small particle sizes. However, many colloidal walled microcapsules are prone to hydration when dispersed in the electrolyte solution used in Coulter measurements. This hydration causes the walls to swell, producing different size analyses dependent upon the time of measurement. In the present work the change in size with time was studied for microcapsules with gelatin-acacia coacervate, or ethylcellulose, walls. The former, although rendered insoluble with formalin, still hydrated; the latter were almost unaffected by water. A sample size of 30 mg was required to prevent blocking of the orifice with larger samples, or too few particles to permit measurement in smaller samples. The coacervate coated microcapsules showed a bimodal distribution, in part due to aggregate of smaller microcapsules, and this distribution changed significantly over the time of measurement. Although the peak due to larger microcapsules did not disappear, the number of large microcapsules fell significantly, most probably because of the disintegration of aggregated microcapsules. Microcapsules with ethyl cellulose walls did not show a bimodal distribution and the particle size analysis did not alter significantly with time.

Subchronic feeding study of carnauba wax in beagle dogs

Carnauba wax fed at levels of 0.1, 0.3 and 1% in the diet to beagle dogs for 28 wk did not produce evidence of toxicity or pathological effects. Body weight gain, food consumption, clinical chemical, haematological, and urine analysis data, and organ weights of animals fed carnauba wax were comparable with those of control animals. Ophthalmic, gross and histopathological examinations revealed no significant treatment-related findings.