White-light toxicity, resulting from systemically administered 5-aminolevulinic acid, under normal operating conditions

This study has investigated damage to the intraperitoneal organs of the rat after systemic (intraperitoneal and intravenous) administration of low dos es of 5-aminolevulinic acid (ALA) and illumination with a standard white-li ght operating-room (o.r.) lamp. The study has been done within the framewor k of a larger study in which the possibility of using ALA for localization of small-volume macroscopically nonvisible peritoneal metastasis of ovarian tumors is being investigated. Fluorescence diagnostics are done in additio n to the standard staging and localization procedures, either through a lap aroscope or during laparotomy. In these circumstances, fluorescence diagnos tics involve some risk of photosensitization of critical organs since a bro ad-band (o.r.) light source is used during the surgical procedures for illu mination of the operating area. The drug dose and the time interval between administration of ALA and illumination an varied and normal tissues are ex amined both macroscopically and microscopically for damage. A relationship is demonstrated between the maximum tolerable dose (MTD) of ALA (defined as the dose that does not cause any tissue damage) and the time interval betw een administration and illumination. The white light that is used for illum ination of the operating area is sufficient to induce damage to the periton eal organs at relatively low ALA doses. The MDTs for 2, 6 and 16 h interval s are found to be respectively 1, 10 and 100 mg kg(-1). The results are sim ilar for both intraperitoneal and intravenous administration. (C) 1999 Else vier Science S.A. All rights reserved.