Study of protoporphyrin IX (PpIX) pharmacokinetics after topical application of 5-aminolevulinic acid in urethral condylomata acuminata

The pharmacokinetics of 5-aminolevulinic acid (ALA)-induced protoporphyrin IX (PpIX) in lesions of urethral condylomata acuminata were investigated. Sixty patients (20 to 60 years old, 48 male and 12 female) were divided randomly into five groups and received topic application of different concentrations of ALA solution (0.5%, 1%, 3%, 5% or 10%). Biopsy was performed between 1 and 7 h and specimens were subjected to histological, PpIX fluorescence and human papillomavirus (HPV) DNA typing analyses. Fluorescence examination confirmed that ALA-induced PpIX fluorescence was dominantly distributed in the HPV-infected epidermis. In contrast, only a minimal amount of PpIX fluorescence was detected in the dermis. The maximal fluorescence intensity was detected at 5 h incubation. Higher ALA concentration (e.g. 5% and 10%) produced a stronger intensity. These results suggest that the topical application of 5-10% ALA solution for 3-5 h is the optimal condition for the photodynamic therapy of urethral condylomata acuminata. The selective damage of the condylomata acuminata lesions in the epidermis without damaging the dermis ensures a better control of recurrence and side effects such as ulceration or scarring. DNA typing showed that all patients were positive for low risk-HPV DNA and among them 18.3% of patients harbored high risk-HPV DNA.