Stability-indicating changes in poloxamers:: the degradation of ethylene oxide-propylene oxide block copolymers at 25 and 40 °C

Poloxamers are block copolymers of ethylene oxide and propylene oxide that are used within the pharmaceutical industry. The stability of poloxamers 188 and 407 at 25 degreesC/60% RH and 40 degreesC/75% RH was studied for 6 months. Poloxamer 407 was stable in both environments, while 188 was degraded at 40 degreesC/75% RH. For the degraded sample, the formation of formic and acetic acid, and formaldehyde and acetaldehyde was seen with time. Molar mass changes were also seen. Both poloxamers contained an antioxidant, although poloxamer 188 contained less than 407, which explains the difference in stability. The acid formation, pH change, aldehyde formation or change in molar mass can be used as a stability-indicating test for poloxamers. The amount of formed acids and aldehydes indicates that the poloxamer is degraded faster initially at the propylene oxide block. (C) 2002 Elsevier Science Ltd. All rights reserved.