Contemporary applications of thermogelling PEO-PPO-PEO triblock copolymers

The poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) triblock copolymers, known as poloxamer (Pluronic (R)), are amphiphilic polymers that possess unique thermo-responsive properties. Several poloxamer grades are FDA-approved and have found applications in many pharmaceutical dosage forms. Though mostly approved for the oral dosage forms, they are also recommended at different concentrations for other routes, including ophthalmic, intravenous, intramuscular, periodontal, and topical. Moreover, numerous studies have been conducted to determine their usefulness in other routes of administration such as intranasal, vaginal, and rectal. In pharmaceutical dosage forms, poloxamers are used to prolong the release, improve the solubility, and enhance the stability and bioavailability of the active agents. Due to their unique thermogelling property, poloxamers have found biomedical applications including in photodynamic therapy, soft tissue engineering, platelet aggregation, cell encapsulation, and glaucoma filtration surgery. However, there are some characteristics of poloxamers that might limit their clinical applications. These include issues with undesirable thermogelling temperature, relatively poor mechanical properties at low polymer content, and premature gelation at high polymer content. Various approaches have been employed to address these issues, which include the addition of viscosity enhancers, salts, and co-solvents. Given their distinctive characteristics, in this review, we aim to discuss the poloxamers pharmaceutical applications.