Sulfathiazole, dissolution rate

Interaction between sulfathiazole and povidone was studied by Raman spectroscopy, and the nature of the drug-polymer coprecipitates investigated [51]. The nature of the drug (solvation state) and its bonding to the polymer were assessed with respect to sulfathiazole dissolution rate. 

Sulfathiazole has been found to crystallize in three distinct polymorphic forms, all of which are kinetically stable in the solid state but two of which are unstable in contact with water [130]. As evident in Fig. 20, the initial intrinsic dissolution rates are different, but as forms I and II convert into form III, the dissolved concentrations converge. Only the dissolution rate of form III was constant during the studies, indicating it to be the thermodynamically stable form at room temperature. Aqueous suspensions of forms I or II were all found to convert into form III over time, supporting the finding of the dissolution studies. Interestingly, around the melting points of the three polymorphs, form I exhibited... 

Simonelli, A. R, S. C. Mehta, and W I. Higuchi. 1969. Dissolution rates of high energy polyvinylpyrrolidone (PVP)-sulfathiazole coprecipitatdSPharm Sc58 538-549. 

Tawashi and Piccolo, gyg examined recent theories of crystal growth and dissolution, and have considered the role of substances which act as inhibitors of these two processes. F.D. C. Blue No.1, at concentrations of 100 mcg,/ml, reduces the dissolution rate of sulfaguanidine by 55%. This finding is consistent with the theory that dye molecules are preferentially adsorbed at the primary dissolution sites on the sulfaguanidine crystal. Polyvinylpyrrolidone inhibits the crystal growth of sulfathiazole. It has been proposed that the polymer forms a non-condensed, netlike film over the sulfathiazole crystal surface. 

Mullin JW (2001) Crystallization, 4th edn. Butterworth-Heinemann, Boston SimoneUi AP, Mehta SC, Higuchi WI (1969) Dissolution rates of high energy polyvinyl pyrrolidone (PVP)-sulfathiazole coprecipitates. J Pharm Sd 58 538-549 Trachenko K (2008) The Vogel-Fulcher-Tammann law in the elastic theory of glass transition. J Non-cryst Solids 354 3903-3906... 

Simonelli AP, Mehta SC, Higuchi WI (1969) Dissolution Rates of High Eneigy Polyvinylpyrrolidone (PVP)-Sulfathiazole Copredpitates. J Pharm Sci 58(5) 538-549... 

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