Formulations microsphere preparation

Several antiinflammatory compounds have been formulated in lactide/ glycolide polymers (107-111). Methylprednisolone microspheres based on an 85 15 DL-lactide/glycolide copolymer were developed for intra-articulate administration (111). The microspheres, prepared by a solvent evaporation procedure, are 5—20 jam in diameter and are designed to release low levels of the steroid over a extended period in the joint. Controlled experiments in rabbits with induced arthritis showed that the microspheres afforded an antiinflammatory response for up to 5 months following a single injection. 

Chitosan microspheres were shown to enhance nasal bioavailability of several peptide drugs such as insulin and goserelin. A simple chitosan-insulin powder formulation provided about 20% of absolute insulin bioavailability in sheep [96], Improved bioavailability (of 44%, in rats) was obtained when insulin was loaded into chitosan microspheres prepared with ascorbyl palmitate as cross-linking agent [91]. Chitosan microspheres have also been shown to improve nasal goserelin absorption providing about 40% bioavailability relative to goserelin intravenous application [9],... 

This chapter gives an overview of parenteral dosage forms and the rational for their use. Parenterals are sterile preparations that are injected intravascularly, administered into body tissues or into visceral cavities. The parenteral route of administration is often chosen for active substances that are poorly absorbed via the oral route or when rapid systemic availability and effects are required, or both. An introduction to the formulation and preparation of parenteral dosage forms is provided. Parenteral medicines can be formulated as solutions, emulsions or suspensions. Products, such as implants and microspheres are only briefly discussed. Knowledge about these types of products is a prerogative for the sound education of patients and caregivers in using the products. 

Journal of Microencapsulation 19, No.4, July-Aug.2002, p.473-84 BIODEGRADABLE BROMOCRYPTINE MESYLATE MICROSPHERES PREPARED BY A SOLVENT EVAPORATION TECHNIQUE. I. EVALUATION OF FORMULATION VARIABLES ON MICROSPHERES CHARACTERISTICS FOR BRAIN DELIVERY... 

Insulin (molecular weight 7000) has been formulated in controlled release microbeads and pellets (135,136). A solvent evaporation micro-encapsulation procedure was used to produce microspheres with up to 20% by weight insulin. Solvent-casting techniques were used to prepare pellets. The investigations demonstrated that the PLA... 

Other Formulations. Neural networks have been applied to the modeling of pellet formulations to control the release of theophylline [63] and to control the rate of degradation of omeprazole [64]. They have also been applied to the preparation of acrylic microspheres [65] and to model the release of insulin from an implant [66]. In arecent study from Brazil, the release of hydrocortisone from a biodegradable matrix has been successfully modeled [67]. 

Pancrelipase is available in both non-enteric-coated and enteric-coated preparations. Pancrelipase enzymes are rapidly and permanently inactivated by gastric acids. Therefore, non-enteric-coated preparations (eg, Viokase tablets or powder) should be given concomitantly with acid suppression therapy (proton pump inhibitor or H2 antagonist) to reduce acid-mediated destruction within the stomach. Encapsulated formulations contain acid-resistant microspheres (Creon) or microtablets (Pancrease, Ultrase). Enteric-coated formulations are more commonly used because they do not require concomitant acid suppression therapy. 

The polyurethane (PU) can be considered an environment-friendly material because the urethane bond resembles the amide bond, which implies possible biodegradability. It can be used in various elastomer formulations, paints, adhesives for polymers and glass, and artificial leather as well as in biomedical and cosmetic fields. Polyurethane spheres were prepared from 20/40% of PU prepolymer solution in xylene [91]. PU droplets were formed in water with the SPG membrane of different pore size (1.5-9.5 pm) and then polymerized to form the final microspheres. Finally, spherical and solid PU particles of 5 pm were obtained after the removal of the solvent. In another study, Ma et al. reported the formation of uniform polyurethane-vinylpolymer (PUU-VP) hybrid microspheres of about 20 pm, prepared using SPG membranes and a subsequent radical suspension polymerization process [92], The prepolymers were solubilized in xylene and pressed through the SPG membrane into the continuous phase containing a stabilizer to form uniform droplets. The droplets were left for chain extension at room temperature for some hours with di- and triamines by suspension polymerization at 70 °C for 24h. Solid and spherical PU-VP hybrid particles with a smooth surface and a higher destructive strength were obtained. 

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