Hyaluronic acid fillers feature key differences, but perform similarly

Key Points

Los Angeles - Many physicians don't understand the key characteristics that differentiate currently available hyaluronic acid (HA) dermal fillers, says Derek H. Jones, M.D., clinical associate professor of dermatology, University of California, Los Angeles.

HA fillers approved or soon to be approved by the Food and Drug Administration (FDA) include Prevelle Silk (Mentor), Juvéderm Ultra and Juvéderm Ultra Plus (Allergan), Restylane and Perlane (Medicis), Hydrelle (Anika) and Belotero (Merz/BioForm), Dr. Jones says.

Belotero's phase 3 studies were published about a year ago (Narins RS, Coleman WP III, Donofrio LM, et al. Dermatol Surg. 2010;36 Suppl 3:1800-1808).

All HA fillers are hydrophilic polymers, and all HA products currently available in the United States are derived from bacteria, Dr. Jones says.

"They may be differentiated in their degree of crosslinking, their concentrations, gel hardness (G prime) and cohesivity. These are all very important characteristics of HAs, and most of them are poorly understood by the majority of cosmetic dermatologists and plastic surgeons who typically use these products," he says.

Juvéderm has the highest concentration (24 mg/cc), followed by Belotero (22 mg/cc) and Restylane (20 mg/cc), he says.

Crosslinking

Crosslinking results in a gel-like product, Dr. Jones says. Medicis essentially pushes this gel through screens with similarly sized holes to produce similarly sized and shaped particles of Restylane.

"Perlane is just a larger particle size; that's the only difference," he says.

Conversely, Dr. Jones says Allergan cuts the HA gel into more randomly sized and shaped particles to produce Juvéderm products. Belotero does not undergo particle sizing or cutting, he says.

"Many people will say that Juvéderm and Belotero are monophasic products," which suggests that uncrosslinked HA is their only ingredient, "but when you get right down to it, there's no true monophasic HA product in the U.S. marketplace," Dr. Jones says. They all contain some degree of free (uncrosslinked) HA, which acts as a lubricant to ease product flow through a syringe. Once this free HA is injected into the body, "It's going to be absorbed pretty quickly, and only the uncrosslinked portion will remain," he says.

Juvéderm is more heavily cross-linked than Restylane, Dr. Jones says. "I'm not sure what the extent of crosslinking is with Belotero," he says. "It's a different form of crosslinking."

In particular, Dr. Jones says Belotero is said to contain variable zones of crosslinking density.

"There are zones where the chains of HA are more heavily crosslinked, and zones where they are less heavily crosslinked," he says.

The purported advantage of the less heavily crosslinked zones is that the Belotero may more effectively fill microscopic areas of dermis that comprise a wrinkle, he says.