Reconstitution of Injectable Poly-d,l-lactic Acid: Efficacy of Different Diluents and a New Accelerating Method

Injectable poly-d,l-lactic acid (PDLLA) is a new collagen-stimulating filler containing PDLLA microspheres and carboxymethyl cellulose. It is available as a lyophilized powder that must be reconstituted with a diluent before administration. The aims of this study were to investigate the efficacy of different diluents and a new accelerating "back-and-forth" method.

Six different diluents, sodium bicarbonate, sterile water for injection (SWFI), normal saline, lidocaine, lidocaine with epinephrine (lidocaine + E), and mannitol, were tested. The recommended "vortex" method for preparation of thin suspensions and a new back-and-forth method suitable for both thin and thick suspensions were compared. Gross and microscopic views of the prepared suspensions were examined.

Using the vortex method, only mannitol and SWFI are found to be effective reconstitution diluents for injectable PDLLA. Using the back-and-forth method, all six diluents can be used for reconstitution of injectable PDLLA. Moreover, the time needed for reconstitution of injectable PDLLA by this back-and-forth method is very short, regardless of the thickness of the suspension.

Clinically, only SWFI can be used for reconstitution of injectable PDLLA by "hand-shaking" or vortex method. To accelerate the reconstitution time especially when using small amount of SWFI, back-and-forth is the method of choice. Besides, when SWFI is not available, other diluents such as normal saline, lidocaine, or lidocaine + E can be used by this novel back-and-forth reconstitution method.