Thermal Behaviour the Ampicillin Drug Substance in Plasma Using DSC-Cooling

摘要

The present study proposes the using of DSC-Cooling with Peltier refrigeration systemrnas tool of ampicillin thermal behavior in human plasma. The ampicillin was submittedrnto a complete thermal studies, that includes: calorimetric profiles, 3 cycles of freezethawingrnisothermal and isothermal behavior. The parameters obtained wererntemperatures onset and transition phase energies of crystallization and melting to verifyrnthe water stability in pure water and water in plasma containing ampicillin. The equationrnof Avrami was used for determination the formation rate and growth mechanism of thernnuclei to kinetic evaluation. DSC-Cooling data of the pure water presented temperaturernonset of 252 K and 272 K, respectively, for the crystallization and melting processes.rnThe plasma presents 99% of water and 1% of macro and micromolecules, such asrnproteins and fats, it showed an anticipation of the temperatures onset of crystallizationrnand melting for 256 K and 271 K, respectively. This can be explained by the capacityrnthat these molecules have to keep energy in comparison with pure water that crystallizesrnin larger temperatures. These data are confirmed by the rate constant and index ofrnAvrami, that are larger for the water (k= 1.08 ± 0.09, n= 1.78 ± 0.12) than for thernplasma (k= 0.67 ± 0.02, n= 1.28 ± 0.06). The ampicillin drug substance did not changernthe thermal parameters in water, but it showed an increase of the temperature onset ofrncrystallization and melting in the human plasma. DSC-Cooling data demonstrated greatrnpotentiality for the freeze-thawing studies of drugs in plasma.