ABSTRACT
Extensive work has been done in the field of drug adjuvant interaction studies using differential scanning calorimetry (DSC), but conclusive interpretive techniques could not be reached since very few workers supplemented their work by conventional isothermal stability testing methods. This work compared the drug adjuvant thermogram with results obtained from isothermal stability studies and used it to reiterate the results of the drug adjuvant thermograms. In the formulation of ascorbic acid in a cosmetic preparation, the various adjuvants were tested for interactions first by the isothermal stability testing technique, which was followed by DSC scanning of the drug adjuvant. The results of the two methods were compared and correlated.
Subject(s)
Adjuvants, Pharmaceutic/chemistry , Ascorbic Acid/chemistry , Calorimetry, Differential Scanning/methods , Absorption , Drug Combinations , Drug Interactions , Drug Stability , Hot TemperatureABSTRACT
PURPOSE: The role of crystal habit in influencing the physical stability and pharmacokinetics of trimethoprim suspensions was examined. METHODS: Different habits for trimethoprim (TMP) were obtained by recrystallizing the commercial sample (PD) utilizing solvent-change precipitation method. Four distinct habits (microscopic observation) belonging to the same polymorphic state (DSC studies) were selected for studies. Preformulation and formulation studies were carried out on suspension dosage forms containing these crystals. The freshly prepared suspensions were also evaluated for their pharmacokinetic behaviour on healthy human volunteers using a cross over study. RESULTS: Variation of crystallization conditions produces different habits of TMP. Among the different crystal habits exhibiting same polymorphic state, the most anisometric crystal showed best physical stability in terms of sedimentation volume and redispersibility. However, habit did not significantly affect the extent of TMP excreted in urine. CONCLUSIONS: Modification of surface morphology without significantly altering the polymorphic state can be utilized for improving physical stability of TMP suspensions. However, the pharmacokinetic profile remains unaltered.
