Decrease of reported adverse events to injectable polylactic acid after recommending an increased dilution: 8-year results from the Injectable Filler Safety study

Background Injectable fillers are widely used in aesthetic medicine. Polylactic acid (PLA) is a semipermanent filler that needs to be diluted with sterile water before injection. PLA has been associated with an increased risk of adverse reactions, specifically nodule formation. Objective To describe adverse reactions to PLA and potential risk factors based on a partly population-based registry over an 8-year period. Methods The Berlin registry is a partially population-based registry where dermatologists, plastic surgeons, and other specialists are contacted regularly and asked to report patients with adverse events to injectable fillers substances. Additional patients were derived from private practices outside of Berlin. The patients were assessed with a standardized questionnaire. The results were mainly analyzed by descriptive measures. Results Twenty-two patients (age, 47.82 +/- 12.65 years) with adverse reactions to PLA were included. The most frequent adverse reaction was nodule formation found in all patients. In 13 (59.1%) of the cases, nodule formation was considered to be severe. Nodules appeared after a mean latency period of 6.00 +/- 5.84 months. The duration of the adverse reactions until the interview was 14.32 +/- 10.13 months. The frequency of patients with adverse events to PLA was found to decrease after new recommendations concerning the dilution of the product were launched. Conclusion PLA is an injectable filler substance that may cause subcutaneous nodules in treated patients. Our data support a decreased risk of adverse reactions with an increased dilution. However, nodule formation still appears to be a characteristic feature of PLA.