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Microencapsulation of the anti-inflammatory drug piroxicam and the anti-asthmatic drug theophylline was investigated as a means of controlling drug release and minimizing or eliminating local side effects. Microspheres of both drugs that are different in the chemical nature and size were successfully encapsulated at a theoretical loading of 25% with the pH sensitive Eudragit S 100 polymer using the emulsion-solvent evaporation method. Solvent composition, stirring rate and the volume of the external phase were adjusted to obtain reproducible, uniform and spherical microspheres. The size distribution of microsphere batches generally ranged from 125-500 microm with geometric means close to 300 microm. Optical light microscopy was used to identify the microsphere shape. Drug loading was determined by completely dissolving the microspheres in an alkaline borate buffer at pH 10. In vitro dissolution studies were carried out on the microspheres at 37 degrees C (+/-0.5 degrees C) at 100 rpm with USP Dissolution Apparatus II using the procedure for enteric-coated products at two successive different pH media (1.2 and 6.5). Both preparations exhibited an initial rapid release in the acidic medium with theophylline showing a larger increase in the amount released during this stage. The drug release was sustained for both preparations at pH 6.5 with theophylline microspheres, showing more extended release. Drug release rate kinetics followed a Higuchi spherical matrix model for both microsphere preparations.

Ibuprofen exhibits poor flow, poor compaction and dissolution behaviour, and it is prone to capping after ejection from the die. Therefore, the aim of the present research was to engineer ibuprofen crystals in the presence of two disintegrants (starch and sodium starch glycolate) in order to improve its flow, compactibility and dissolution behaviour simultaneously. To this end ibuprofen and different concentrations of disintegrant (0.25 to 10% w/w in case of starch and 0.25 to 7% w/w in case of sodium starch glycolate) were dissolved in ethanol and water respectively. The ibuprofen solution was then added to the aqueous solutions containing the different concentrations of disintegrant. Ibuprofen precipitated within 10 min and the crystals were separated and dried for further studies. The obtained crystals were characterized in terms of flow, density, tablet hardness, dissolution behaviour and solid state. The results showed most of engineered ibuprofen to have better flow with a high compactibility. The results also showed that an increase in the concentration of starch in the crystallization medium resulted in a reduction in the hardness of ibuprofen tablets, but this was not the case for ibuprofen samples engineered in the presence of sodium starch glycolate. It is interesting to note that although engineered ibuprofen showed superior dissolution as compared to untreated ibuprofen, the highest concentration of starch (10%) or sodium starch glycolate (7%) slowed down the release remarkably due to an increase in the viscosity of the dissolution medium around drug particles. Solid state analysis (FT-IR, XRPD and DSC) ruled out the presence of different polymorphic forms and also any interaction between these disintegrants and ibuprofen. In conclusion, the engineering of ibuprofen in the presence of disintegrant showed how properties such as flow, compaction and dissolution behaviour can be simultaneously manipulated to suit a desired application

Several methods and techniques are potentially useful for the preparation of polymeric microparticles in the broad field of microencapsulation. The preparation method determines the type and the size of microparticle and influence the ability of the interaction among the components used in microparticle formulations. This review is devoted to describe and allocate the recently awarded and pending patents regarding the technical and formulation innovations in microparticles involved in drug delivery that are based mainly on the emulsion solvent removal methods. The term microparticle designates systems larger than one micrometer in diameter and is used usually to describe both microcapsules and microspheres. Microparticle-containing drugs are employed for various purposes including--but not restricted to--controlled drug delivery, masking the taste and odor of drugs, protection of the drugs from degradation, and protection of the body from the toxic effects of the drugs. Polymeric carriers being essentially multidisciplinary are commonly utilized in microparticle fabrication and they can be of an erodible or a non-erodible type.

The aim of this work was to prepare and evaluate Tadalafil nanosuspensions and their PEG 4000 solid dispersion matrices to enhance its dissolution rate. Nanosuspensions were prepared by precipitation/ultrasonication technique at 5°C where different stabilizers were screened for stabilization. Nanosuspensions were characterized in terms of particle size and charge. Screening process limited suitable stabilizers into structurally related surfactants composed of a mixture of Tween80 and Span80 at 1:1 ratio (in percent, weight/volume) in adjusted alkaline pH (named TDTSp-OH). The surfactant mixture aided the production of nanosuspensions with an average particle size of 193 ± 8 nm and with short-term stability sufficient for further processing. Solid dispersion matrices made of dried Tadalafil nanosuspensions or dried Tadalafil raw powder suspensions and PEG 4000 as a carrier were prepared by direct compression. Drying was performed via dry heat or via freeze dry. Drug release studies showed that, in general, tablet formulations made of freeze-dried product exhibited faster initial release rates than the corresponding tablets made of oven-dried products which could be attributed to possible larger crystal growth and larger crushing strengths of oven-dried formulations. At best, 60% of drug was released from solid dispersion matrices, while more than 90% of drug was released from TDTSp-OH nanosuspension within the first 5 min. In conclusion, Tadalafil nanosuspensions obtained using a mixed surfactant system provided rapid dissolution rates of Tadalafil that can theoretically enhance its bioavailability.

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The objectives of this investigation are to evaluate the effect of the viscosity of polymer solution phase on microsphere properties, especially the drug release characteristics since no studies on this formulation variable have been reported. Also, since it is known that polymer molecular weight affects both the viscosity of the polymer solution and the release properties of microspheres, the interaction of these factors was studied. Microspheres with 33% theoretical drug loading of anhydrous theophylline core material were prepared by the emulsion solvent evaporation method. Two cellulose acetate butyrate polymers, (CAB381-2, CAB381-20), chemically similar but having different molecular weights, were used to prepare different polymer solutions having different apparent viscosities in acetone. A Brookfield viscometer was used to evaluate the viscosities of polymer solutions. Dissolution rates of microspheres prepared from the polymer solutions were inversely related to the initial polymer solution viscosities for both CAB381-2 and CAB381-20. The times for the release of 30 and 50% of the drug from the microspheres have a linear relationship with initial polymer solution viscosity. Initial release was significantly decreased with increasing polymer solution viscosity. Unlike CAB381-2 microspheres which follow Higuchi spherical matrix release kinetics, microspheres prepared from the higher molecular weight polymer (CAB381-20) showed extended release dissolution profiles with near zero order kinetics. It is evident that both the polymer solution viscosity and the molecular weight have an effect on the drug release from microspheres. These results suggest that release rates of matrix microspheres could be predictably optimized by adjusting the viscosity of polymer solutions.

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