Adverse Drug Reaction Attributable to Aluminum Phthalocyanine Tetrasulphonate Administration in Domestic Cats

Phthalocyanines are currently under investigation as photosensitizers for use in photodynamic therapy (PDT). We have been examining the efficacy of PDT in Domestic cats that have been treated for nasal and aural squamous cell carcinomas (SCC) using the photosensitizer aluminum phthalocyanine tetrasulphonate (AIPCS,) (Porphyrin Products, Logan, UT). Both clinical treatment and pharmacokinetic experiments have involved a total of 63 random-bred mature cats, considered normal on the basis of physical examinations, pretreatment serum chemistry profiles, and hematologic screens. Cats with positive tests for feline leukemia virus or feline immunodeficiency virus were excluded. Fortyfive of these cats had SCC and were treated one to three times with PDT using AlPCS,. Owners of cats failing therapy were requested to donate their cats for use in pharmacokinetic studies of AlPCS,. Pharmacokinetic studies were also performed using 18 cats that did not have SCC. These cats were obtained solely for pharmacokinetic experiments and received only one AlPCS, injection. All cats in either treatment or pharmacokinetic studies were injected intravenously with 2.0 mg/kg AlPCS,, which was prepared by dissolving AlPCS, in phosphate-buffered saline to a concentration of 2 mg/rnl and adjusting the pH to 7.35 with 0.1 N NaOH. The solution was passed through a 0.45-wm filter prior to injection. There were at least 45 days between injections in cats treated clinically more than once and in cats that failed treatment and entered pharmacokinetic studies. Cats in treatment studies were irradiated 24 hours after injection with 675-nm light from an argon