Abstract: OBJECTIVE: To observe the photobleaching characters of sinoporphyrin sodium (DVDMS) in different solutions and skins of animal. METHODS: Absorption peaks of DVDMS (10, 20, 40 μg/mL) in normal saline (NS), RPMI-1640 medium (RPMI-1640), RPMI-1640 medium containing 10% fetal calf serum (RPMI-FBS) and suspension of HaCaT cells were measured using micro-spectrophotometer. Using DVDMS solutions with concentrations of 1, 2.5, 5, 10, 20 and 40 μg/mL in the 4 solvents above, photobleaching of DVDMS after laser radiation for 3, 6, 10, 20, 40, 50, 60, 120, 180 min was observed using microplate reader. In vivo image acquisition system was used to study the distribution of DVDMS in animal skins, and the bleaching after irradiation in psoriasis-like animal skins were also observed. RESULTS: DVDMS with concentrations 10, 20 and 40 μg/mL showed obvious characteristic absorption peaks in the 4 solutions. Photobleaching occurred in the 4 solutions under the irradiation conditions used in previous pharmacodynamics studies (laser radiation was 3 minutes). Two-phase processes photobleaching (fast first phase and second slow phase) of DVDMS were observed in 180 min. The distributions of DVDMS in skins of normal and psoriasis-like animal were uniform, obvious photobleaching occurred in skins of psoriasis-like animal after laser irradiation with dose of 9.6 J/cm². CONCLUSION: In vitro photobleaching of DVDMS was influenced by light dose, initial concentrations and solvents. Secondary-dynamic model was suitable to describe the photobleaching progress. Photobleaching occurred in skins of psoriasis-like animal after laser irradiation.

Key words: sinoporphyrin sodium, laser, photobleaching, psoriasis