Photodynamic therapy of the rat endometrium by systemic and topical administration of tin ethyl etiopurpurin

The objective of this study was to determine the optimal parameters for end ometrial destruction by photodynamic therapy (PDT) using tin ethyl etiopurp urin (SnET2) as a photosensitizer in the rat model. Different application r outes and different time intervals after drug administration were compared when the uterine horn was illuminated with a fixed laser light dose of 375 J/cm(2). Then PDT was performed 1.5 h after IV injection of 2 mg/kg SnET2 u sing decreasing light doses. Destruction of all endometrial glands was obse rved when the uterine horn was illuminated 1.5 h after IV drug administrati on. In contrast, weaker PDT effects were observed when light activation was delayed for 24 h following systemic or topical drug application even if th e light dose was increased by a factor of 30. Endometrial fluorescence did not prove to be an effective method to predict optimal timing for photodyna mic therapy, which was probably due to its binding to serum proteins. For p hotodynamic treatment of endometrial glands in the rat, IV administration 1 .5 h before illumination was most efficient.