Aminolevulinic acid (ALA) is being used as a "
prodrug" for
photodynamic therapy. The side effects of ALA have been only anecdotally reported and these effects as well as pharmacokinetics of the photosensitizing end product of ALA,
protoporphyrin IX (
PpIX), in patients undergoing operation are unknown. This study systematically determines the side effects of ALA and pharmacokinetics of
PpIX in patients undergoing abdominal surgery. Patients were given 30 or 60 mg/kg ALA preoperatively, kept in subdued light for 48 hr, and monitored clinically and with laboratory tests for 5 to 7 days and for at least 2 months thereafter. Periodic plasma samples and tissue biopsies were analyzed for
PpIX concentrations using a photodiode array system. No patient developed symptoms of
porphyria other than
nausea and
vomiting, which occurred in 20%. Nearly one-quarter of patients developed transient abnormal liver functions. No patient developed cutaneous
phototoxicity, abnormal neurologic function, or unexpected postoperative laboratory tests. The times of peak plasma, skin, skeletal muscle, omental, mucosal, muscularis mucosal, and
tumor concentrations of
PpIX varied among patients. In general,
PpIX concentrations were significantly greater with the higher dose of ALA.
Tumor PpIX concentrations were significantly greater than in other tissues except liver. In conclusion, ALA, up to 60 mg/kg, is associated with minimal side effects in patients undergoing operation. Actual tissue concentrations of
PpIX suggest that endogenous
photosensitization using systemically administered ALA is a mode of
PDT feasible for treatment of
adenocarcinomas of the gastrointestinal tract in humans.