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Abstract

A congealable disperse phase encapsulation method was used to prepare sustained-release ibuprofen-wax microspheres. Microspheres prepared with paraffin wax, such as ceresine and microcrystalline waxes, using polyvinylpyrrolidone (PVP) as dispersant had a tendency to aggregate, but the addition of wax modifiers (stearyl alcohol and glyceryl monostearate) greatly reduced aggregation. Optimum modifier and dispersant concentrations were 20% (w/w) and 5% (w/v), respectively. The particle size distribution of the microspheres was log-normal. An increase in modifier, dispersant concentration, emulsification stirring speed, or temperature shifted the size distribution toward finer particles. Microcrystalline wax required a higher emulsification temperature and produced finer particles than ozokerite wax. The recovery of drug from the different microsphere formulations varied between 71 and 92%. Differential scanning calorimetry (DSC) of the single components and physical mixtures showed endothermic peaks at the respective melting-point ranges. The DSC of the ceresine and microcrystalline wax microspheres was similar to rescans of ternary mixtures of components of the microspheres with less prominent and lower melting temperatures than individual components or physical mixtures.

Sustained release biodegradable solid lipid microparticles: Formulation, evaluation and statistical optimization by response surface methodology

“…-For bulk density (r b ) calculation, the bulk volume (V b ) occupied by a pre-weighed amount of SLMs (m) was observed from a graduated cylinder. Bulk density was calculated with the help of the following formula (4,19):…”

“…-For tapped density measurement, a graduated cylinder having a preweighed amount of SLMs was tapped for a specified number of tapings so that SLMs attained a plateau condition. The tapped volume (V t ) occupied by SLMs after tapping was observed (4,19). Calculation of tapped density (r t ) was performed using the of following formula;…”

“…Oral sustained release formulations have been gaining ample consideration over the last three decades because of their significant therapeutic benefits such as flexibility in formulation, ease of administration and particularly enhanced patient compliance. Microspheres, particularly based on natural biodegradable lipids (solid lipid microparticles) have attracted significant attention for offering sustained drug delivery (3)(4)(5).…”

“…SLMs exhibit enhanced physical stability, safety, biocompatibility; they improve drug aqueous solubility and provide higher plasma drug availability with improved membrane permeability (4)(5). Moreover, they are characterized by dual loading ability (i.e.…”

“…lipophilic and hydrophilic drugs) and are suitable and economical for large scale production (2). SLMs can prolong residence time at the absorption site (2) and can be formulated from solid lipids such as carnauba wax (CW) and glyceryl monostearate (GMS) because they exhibit excellent biocompatibility, biodegradability (4), lack of toxicity and ease of production (4)(5)(6). CW and GMS SLMs can make drug release sustained and enhance drug bioavailability (2-3).…”