Design and Development of Controlled Porosity Osmotic Pump Tablets of Zidovudine Using Sodium Chloride as Osmogen for the Treatment of Aids

The present study investigates the feasibility of the design and develops controlled porosity osmotic pump (CPOP) tablets to prolong the drug release of an antiretroviral drug zidovudine of 600mg once daily. Five formulations (ZS1to ZD5) were prepared by wet granulation method using various excipients. The CPOP consisted of an osmotic core coated with a micro porous membrane made up of cellulose acetate, poly ethylene glycol and sorbitol as in situ micro pore former. The prepared tablets were evaluated for pre compression parameters, post compression parameters, in vitro drug release study, Fourier Transform Infrared Spectroscopy (FTIR) study, Differential Scanning Calorimetry (DSC) study and scanning electron microscopy (SEM) study. The formulation variables such as effect of osmogen concentration, effect of pore former concentration, effect of membrane thickness of semi permeable membrane were evaluated for drug release characteristics. For the optimized formulation (ZS4) effect of osmotic pressure, effect of pH and effect of agitation intensity was evaluated. The in vitro release kinetics were analyzed for different batches by different pharmacokinetic models such as zero order, first order, Higuchi, Korsmeyer-Peppas and Hixson-Crowell model. The result of optimized formulation releases drug up to 16 hrs in a controlled manner and follows Higuchi kinetics and which is independent of the pH and agitation intensity. The optimized formulation was found to be stable up to 3 months when tested for stability study at 40±2ºC/ 75±5% RH

Influence of Velocity Gradient on Optimisation of the Aggregation Process and Properties of Formed Aggregates

Influence of Velocity Gradient on Optimisation of the Aggregation Process and Properties of Formed Aggregates The follow up research into the IHDS process was carried out with a Couette device. The outcome of this study provides a comprehensive understanding of the effect that both the agitation intensity and the agitation time have on the kinetics and the mechanism of the aggregation process. The results obtained confirm the very favourable influence of high agitation intensity for the formation of more compact and dense aggregates than those formed by the accustomed flocculation conditions with low agitation intensity. This research also proved that the agitation intensity and time are the inherent means profoundly influencing the properties of the resultant aggregates such as their size, shape, density and homogeneity. Further, it was confirmed that the aggregation process passes through a minimum. Furthermore, it was verified that the aggregation process takes place in four consecutive phases, namely a) the phase of formation, b) the phase of compaction, c) the phase of a steady (equilibrium) state and d) most probably the phase of inner restructuring. The pattern of the aggregates development in these phases remains the same irrespective of the magnitude of the velocity gradient applied but the time at which these phases are completed is velocity gradient dependent. Last but not least this study proved that the dimensionless product Ca = G T = const. has no general validity.

INFLUENCE OF VELOCITY GRADIENT ON OPTIMISATION OF THE AGGREGATION PROCESS AND PHYSICAL PROPERTIES OF FORMED AGGREGATES: Part 1. Inline high density suspension (IHDS) aggregation process

INFLUENCE OF VELOCITY GRADIENT ON OPTIMISATION OF THE AGGREGATION PROCESS AND PHYSICAL PROPERTIES OF FORMED AGGREGATES: Part 1. Inline high density suspension (IHDS) aggregation processThis paper deals with optimisation and acceleration of the clarification process. It was established that both these objectives are closely inter-related and can be accomplished by the formation of aggregates with a high agitation intensity until the flocculation optimum is reached. This is a new method of formation of aggregates which is called the Inline High Density Suspension (IHDS) formation process. Further, under the IHDS process the aggregates are formed with a single root-mean-square velocity gradientG>> 50 s-1. It was also established that the process of formation of aggregates (expressed by residual e of the observed determinant) passes through a minimum. This minimum is considered to be the flocculation optimum. Furthermore, the agitation intensity (G) was found to be the inherent means influencing compactness and thereby density of the aggregates formed. This proves the vital role of agitation intensity on the morphological and physical properties of aggregates formed. The resultant aggregates formed by the IHDS process are very compact, dense and homogeneous in their size, shape, volume and inner structure. Last but not least, the IHDS process applied to the HR-CSAV type sludge blanket clarifier facilitated its high attainable upflow velocity above of 25 m h-1.