ABSTRACT
Objective: Diverse studies have demonstrated that no single method of dissolution testing is suitable for different types of suppository dosage forms by either current USP and Ph.Eur methodologies. The objective of the research work was to overcome the methodological problem and limitations by a novel modified basket method
Materials and Methods: USP dissolution apparatus-I was modified by placing a dialysis membrane of specific molecular weight cut off to prevent any kind of clogging which may give irreproducible, inconsistent results. Physical properties like melting range, liquefaction and solidification time, disintegration time and mechanical strength were studied as per Ph.Eur III
Results: The amount of drug released from water soluble bases were fast with 94.5 1.8 %, 96.8 2.2% during 1h and slow with lipophilic bases with 91.6+/-2.3% and 92.7%+/-3.7% respectively during 6h. There was no significant difference between the dissolution profiles by flow through cell and modified basket method [P>0.005]. Average lag time was 8.2, 9.8 min for water soluble suppositories and 14.4 and 11.8 min for lipophilic suppositories respectively. Release kinetics showed first order release rate for water miscible suppositories and zero order release profiles for lipophilic suppositories till 3 h and first order release after this time interval. Disintegration time of water soluble suppositories was 12-15 min but lipophilic suppositories demonstrated an extended disintegration time of 20-22 min Determination of plastic viscosity versus temperature indicated higher yield value for fatty bases compared to water soluble bases
Conclusion: Based on the data, it was concluded that proposed method could be used as a substitute for flow through cell of Ph.Eur. We further hypothesized that change in viscoelastic behavior due to the variation in temperature and aging may be responsible for the differences in the dissolution behavior between different suppositories bases
ABSTRACT
Objective: The Primary objective of the present investigation was to stabilize ascorbic acid by blocking its irreversible conversion to biologically inactive form. Further aim of the project was to disperse stabilized ascorbic acid in internal aqueous phase of multiple emulsions and deliver it in a suitable base for topical application and enhanced transdermal permeation
Materials and Methods: The o/w/o emulsions were formulated by a two-step emulsification procedure, with different types and ratios of surfactant and oil using sodium oxalate as a stabilizer. Physical and chemical stability of the optimized formulation was evaluated at 8[degree sign]C, 25[degree sign]C, 40[degree sign]C and 40[degree sign]C /75% relative humidity. Physical stability of the formulation was determined by organoleptic characteristics, globule size, viscosity, pH and conductivity. Ascorbic acid release profile was measured with Franz diffusion cell using sigma membrane
Results: There was no change in color or liquefaction was observed in primary or multiple emulsion stored at 8[degree sign]C, 25[degree sign]C, 40[degree sign]C and 40[degree sign]C/75% relative humidity for a period of 6 months. Physical stability studies revealed change in globule size, phase separation and increase in pH for all primary and multiple emulsions kept at 40[degree sign]C and 40[degree sign]C/75% relative humidity. But there was only marginal change in pH and conductivity, globule size, and rheological parameters for multiple emulsions stored at 25[degree sign]C. In vitro release study showed that multiple emulsions followed a zero order release rate with an average flux value of 0.125 micro g/cm[2] /min
Conclusion: Based on the data, it was proved that multiple emulsion using sodium oxalate as a stabilizer remarkably improved the stability of ascorbic acid in aqueous solutions. The data given in this research led us to conclude that stabilized multiple w/o/w emulsion could be employed as a potential prolonged release vehicle for topical application of ascorbic acid