Dipen Desai

Excipients for Amorphous Solid Dispersions

Pharmaceutical excipients play a significant role in stabilization of amorphous solid dispersions, as these systems are thermodynamically unstable. This chapter illustrates the challenges associated with amorphous solid dispersion stability and the role that excipients play in stabilization of amorphous solid dispersions by influencing the physicochemical properties of the drug molecule of interest. The classification of various excipients is categorized in detail, covering polymers, solubilizers, plasticizers, antioxidants, and other suitable fillers. The impact of excipients on various amorphous solid dispersion technologies is also discussed in detail. Discovery of newer polymers and greater understanding of excipients’ role in the stabilization of amorphous solid dispersion are the primary reasons for successful launch of several marketed drug products. In addition, safety and regulatory aspects of these excipients also need to be considered for the development of successful products. In summary, excipients play a significant role in stabilizing amorphous solid dispersions, maximizing bioavailability, and overcoming absorption issues associated with poorly soluble drugs.

Evaluation of selected micronized poloxamers as tablet lubricants.

The primary objective of this study was to compare the lubrication properties of micronized poloxamer 188 (Lμ trol micro 68®) and micronized poloxamer 407 (Lμ trol micro 127®) with certain conventional lubricants such as magnesium stearate and stearic acid. The secondary objective was to use these micronized poloxamers as water-soluble tablet lubricants in preparation of effervecsent tablets. The results showed that these micronized poloxamers have superior lubrication properties compared with stearic acid, with no negative effect on tablet hardness, friability, disintegration, or dissolution. Moreover, lubricant mixing time had no significant effect on tablet properties when poloxamers were used as lubricants. Effervescent tablets also were produced successfully using micronized poloxamers as lubricants. The micronized poloxamers had a better lubrication effect in compariason with that of water-soluble lubricant l-leucine.

Selection of Solid-State Plasticizers as Processing Aids for Hot-Melt Extrusion

The objective of the study was to select solid-state plasticizers for hot-melt extrusion (HME) process. The physical and mechanical properties of plasticizers, in selected binary (polymer:plasticizer) and ternary (active pharmaceutical ingredient:polymer:plasticizer) systems, were evaluated to assess their effectiveness as processing aids for HME process. Indomethacin and Eudragit® E PO were selected as model active pharmaceutical ingredient and polymer, respectively. Solubility parameters, thermal analysis, and rheological evaluation were used as assessment tools. Based on comparable solubility parameters, stearic acid, glyceryl behenate, and polyethylene glycol 8000 were selected as solid-state plasticizers. Binary and ternary physical mixtures were evaluated as a function of plasticizer concentration for thermal and rheological behavior. The thermal and rheological assessments also confirmed the miscibility predictions from solubility parameters. The understanding of thermal and rheological properties of the various mixtures helped in predicating plasticization efficiency of stearic acid, glyceryl behenate, and polyethylene glycol 8000. The evaluation also provided insight into the properties of the final product. An empirical model was also developed correlating rheological property of physical mixtures to actual HME process. Based on plasticizer efficiency, solid-state plasticizers and processing conditions can be selected for a HME process.

Effect of formulation and processing variables on the granulation kinetics of hot melt granulation (HMG) process

The objective of the study was to evaluate the effect of formulation factors, such as type of drug and particulate properties of a drug, and processing variables, i.e. jacket temperature, impeller speed, and scale, on granulation kinetics the of hot-melt granulation (HMG) process. Two model active pharmaceutical ingredients (API) Ro-A and indomethacin were selected for this evaluation using poloxamer 188 as a meltable binder. The effect of solid-state properties of API was investigated for Ro-A, whereas the binder properties were maintained constant. General factorial design was used to investigate the effect of independent process variables, impeller speed and jacket temperature using impeller motor power consumption as response variable. Consistent granulation could be developed for Ro-A by optimizing the binder level and impeller speed, however, the addition of third excipient was necessary for indomethacin. The granulation rate was related to the bulk density and the surface area of the drug. The jacket temperature affected overall granulation time but had no significant effect on the granulation kinetics, suggesting that faster heating rate is desirable for optimal productivity. A significant increase in the granulation rate was observed with increase in impeller speed. The effect of impeller speed was further confirmed at 5 L and 25 L scale. From the formulation prospective, the critical factors were the level of binder, inherent binding properties of the API, the solid-state properties of API and binder. From processing perspectives, the impeller speed had a significant effect on the granulation kinetics.