Stabilised suspending efficiency of Laponite XLG and sodium carboxy methylcellulose blend in the formulation of sulphamerazine suspension

Abstract

Charged drugs like Sulphamerazine may make pseudoplastic/plastic materials become Newtonian and loose their suspending power. In this study, laponite XLG (laponite), a synthetic hectorite was employed as a protective colloid and viscosity stabilizer in a blend with sodium carboxymethylcellulose (SCMC), which exhibits high viscosity at low rates of shear and shear thinning characteristics. The viscosities and yield values of suitable concentrations (2%w/w SCMC, 4%w/w laponite, and a 1:1 ratio of 2%w/w laponite – SCMC blend) that yielded pseudoplastic/plastic properties were studied in the absence and presence of 1 - 4%w/w sulphamerazine. For this purpose, the rheograms of the systems were obtained by the use of a Haake rotoviscometer RV 12 utilizing a cup and rotor sensor system MV 1. In the absence of sulpamerazine, the blend had higher viscosity and yield value than either material alone, which were resistant to change in the presence of sulphamerazine. The blend was consequently very efficient in suspending sulphamerazine powder with no separation. Laponite changed from a pseudoplastic to a Newtonian fluid in the presence of sulphamerazine, but gave a flocculated suspension with a clear supernatant and a large sedimentation volume that was readily redispersed. SCMC on the other hand, allowed the sedimentation of sulphamerazine with low sedimentation volume and misty supernatant. The sediment was also difficult to redisperse, suggesting a deflocculated system. Laponite – SCMC blend could be a very useful and efficient suspending agent in the liquid formulation of difficult insoluble drugs, including magnesium trisilicate whose many marketed forms often show separation. Key words: Laponite XLG,sodium; Carboxymethylcellulose and their blend; Suspending efficienc; Sulphamerazine suspension. Nig. J. Pharm. Res. 3(1) 2004: 56-60