Biodistribution of three photosensitizers in dogs with spontaneous tumors.

Photodynamic therapy (PDT) has been considered a potential method for tumor eradication. The present study was designed to assess the efficacy of PDT as an alternative treatment approach. Photosensitizers, such as porfimer sodium, tin ethyl etiopurpurin, and aluminum chlorophthalocyanine, were administered i.v. to dogs, and tissue samples were harvested 24 to 300 hours later. The uptake of the photosensitizers in tumor (fibrosarcoma) and adjacent normal tissue biopsies was quantified by tissue solubilization technique and fluorimetry. In addition, the pharmacokinetics and selectivity of the photosensitizers were addressed by two-phase exponential function and specific uptake ratio, respectively. Porfimer sodium exhibited a longer elimination half-life (175.3 hr), slower clearance (0.0028 L/kg/hr), and a larger area under the curve (1075 microg/g/hr) in tumors than did tin ethyl etiopurpurin or aluminum chlorophthalocyanine. As a result, porfimer sodium showed a good selectivity in tumors located in muscle and skin. The study provided clinical information for determination of the efficacy of different PDT alternatives.