level: Level 3 of Thermodynamics (PHYSICAL DEGRADATION)
Questions and Answers List
level questions: Level 3 of Thermodynamics (PHYSICAL DEGRADATION)
| Question | Answer |
|---|---|
| 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 give | different 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 excipients | Vapor Phase Transfer Including Sublimation |
| Examples of Vapor Phase Transfer Including Sublimation | Nitroglycerin; 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 appearance | Moisture Absorption |
| one of the primary factor affecting the stability | TEMPERATURE AS PHYSICAL FACTOR |
| • Freezing is often assumed to slow degradation process but not in aqueous solutions, where it increases degradation | STABILITY IN FROZEN STATE |
| • The PH degradation effect can be explained by | catalytic effect of hydroxide and hydronium ion |