UC Irvine

The objective of this study was to determine the optimal parameters for endometrial destruction by photodynamic therapy (PDT) using tin ethyl etiopurpurin (SnET2) as a photosensitizer in the rat model. Different application routes and different time intervals after drug administration were compared when the uterine horn was illuminated with a fixed laser light dose of 375 J/cm2. Then PDT was performed 1.5 h after IV injection of 2 mg/kg SnET2 using decreasing light doses. Destruction of all endometrial glands was observed when the uterine horn was illuminated 1.5 h after IV drug administration. In contrast, weaker PDT effects were observed when light activation was delayed for 24 h following systemic or topical drug application even if the light dose was increased by a factor of 30. Endometrial fluorescence did not prove to be an effective method to predict optimal timing for photodynamic therapy, which was probably due to its binding to serum proteins. For photodynamic treatment of endometrial glands in the rat, IV administration 1.5 h before illumination was most efficient.