Tissue levels, histologic changes and plasma pharmacokinetics of meta-tetra (hydroxyphenyl) chlorin (mTHPC) in the cat

The biodistribution and pharmacokinetics of meta-tetra(hydroxyphenyl)chlorin (mTHPC)(1) have been documented in humans, rats, dogs and rabbits. It has been demonstrated to be an effective photodynamic therapy agent for treatment of squamous cell carcinoma. Squamous cell carcinoma is a common feline neoplasm, causing significant morbidity and mortality in the feline population. The association between ultraviolet radiation exposure and occurrence of this neoplasm in the cat provides a useful model for the study of human cutaneous squamous cell carcinoma. In this study, we document the biodistribution, pharmacokinetics and toxicity of mTHPC in a group of normal cats. Four groups of cats were given the drug intravenously at dosages of 0, 0.15, 0.30 and 0.60 mg/kg. mTHPC levels were measured in plasma and tissues at 0, 24, 48, 72, 96 and 336 h after drug administration. Additionally, plasma samples were collected at 1 and 6 h post-injection and analysed. Biodistribution and pharmacokinetics of mTHPC in cats mirrors that in other animal species. There were no clinical or pathological changes associated with administration of the drug. The biodistribution and pharmacokinetics of mTHPC in cats mirrors that in other species studied. There were no clinical or pathological changes attributable to administration of the drug at the doses administered. mTHPC may be a useful photodynamic therapy drug in cats.