Abstract
The present research was aimed at the enhancement of the dissolution rate of atorvastatin calcium by the solid dispersion technique using modified locust bean gum. Solid dispersions (SD) using modified locust bean gum were prepared by the modified solvent evaporation method. Other mixtures were also prepared by physical mixing, co-grinding, and the kneading method. The locust bean gum was subjected to heat for modification. The prepared solid dispersions and other mixtures were evaluated for equilibrium solubility studies, content uniformity, FTIR, DSC, XRD, in vitro drug release, and in vivo pharmacodynamic studies. The equilibrium solubility was enhanced in the solid dispersions (in a drug:polymer ratio of 1:6) and other mixtures such as the co-grinding mixture (CGM) and kneading mixture (KM). Maximum dissolution rate was observed in the solid dispersion batch SD3 (i.e. 50% within 15 min) with maximum drug release after 2 h (80%) out of all solid dispersions. The co-grinding mixture also exhibited a significant enhancement in the dissolution rate among the other mixtures. FTIR studies revealed the absence of drug-polymer interaction in the solid dispersions. Minor shifts in the endothermic peaks of the DSC thermograms of SD3 and CGM indicated slight changes in drug crystallinity. XRD studies further confirmed the results of DSC and FTIR. Topological changes were observed in SEM images of SD3 and CGM. In vivo pharmacodynamic studies indicated an improved efficacy of the optimized batch SD3 as compared to the pure drug at a dose of 3 mg/kg/day. Modified locust bean gum can be a promising carrier for solubility enhancement of poorly water-soluble drugs. The lower viscosity and wetting ability of MLBG, reduction in particle size, and decreased crystallinity of the drug are responsible for the dissolution enhancement of atorvastatin. The co-grinding mixture can be a good alternative to solid dispersions prepared by modified solvent evaporation due to its ease of preparation and significant improvement in dissolution characteristics.
Highlights
Advancements in molecular screening methods for potential drug molecules led to the identification of an increasing number of poorly water-soluble drugs
The current study investigates the impact of modified locust bean gum (MLBG) on the solubility enhancement of the poorly watersoluble drug, atorvastatin calcium
The results revealed a decrease in viscosity of MLBG with almost the same swelling index and hydration capacity as compared to LBG
Summary
Advancements in molecular screening methods for potential drug molecules led to the identification of an increasing number of poorly water-soluble drugs. Solid dispersions (SD) have created considerable interest as the potential means of improving the dissolution rate and the bioavailability of poorly water-soluble drugs. Studies using modified forms of the natural polymers such as locust bean gum (LBG), guar gum, and gum karaya (desired swelling and reduced viscosity characteristics) have been reported for preparing solid dispersions of hydrophobic drugs [5,6,7]. LBG is a natural polymer, extracted from the seeds (kernels) of the carob tree Ceratonia siliqua (Family Leguminosae or Fabaceae) and known as carob bean gum or carubin. It is used as a thickening and stabilizing agent. Solubility enhancement of atorvastatin has been revealed through various experimental evidences such as salt formation [12] and inclusion complexes with
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