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level: Level 3 of Thermodynamics (PHYSICAL DEGRADATION)

Questions and Answers List

level questions: Level 3 of Thermodynamics (PHYSICAL DEGRADATION)

QuestionAnswer
Crystallization of amorphous• Amorphous state is more soluble than crystalline state • Solubility is major problem in different dosage forms, the amorphous state is mostly considered • But amorphous substance is high in free energy and entropy and leads towards stability problem • Long term storage of amorphous substance resulted in change in crystal habit
Stability changes of Nifedipine under different storage conditions givedifferent dissolutions
Transition in Crystalline State• Polymorphs are the different crystalline forms of the single drug • Polymorphic transition can change the critical properties of drug
Examples of Transition in Crystalline State• Two crystalline forms of benoxaprofen • Three crystalline forms of bromovalerylurea • Two forms of pyridoxal chloride where transition between hydrated and anhydrated form exist in various drugs
• Pharmaceuticals containing components that sublime easily may undergo changes in drug content owing to the sublimation of the drug substances or excipientsVapor Phase Transfer Including Sublimation
Examples of Vapor Phase Transfer Including SublimationNitroglycerin; the transfer can be stopped by polyethyleneglycol peg or other water soluble non volatile agents
• Mostly observed in solid dosage form • can cause physical instability of drugs by changing color and appearanceMoisture Absorption
one of the primary factor affecting the stabilityTEMPERATURE AS PHYSICAL FACTOR
• Freezing is often assumed to slow degradation process but not in aqueous solutions, where it increases degradationSTABILITY IN FROZEN STATE
• The PH degradation effect can be explained bycatalytic effect of hydroxide and hydronium ion