Phototoxic reactions in healthy volunteers following photodynamic therapy with methylaminolevulinate cream or with cream containing 5-aminolevulinic acid: a phase II, randomized study.

Background: Photodynamic therapy (PDT) is the selective destruction of abnormal cells through activation of a photosensitizer in the presence of oxygen. Local phototoxic reactions and pain are the most common limiting side effects.

Purpose: The primary objective was to compare the local phototoxic response following PDT with methylaminolevulinate (MAL) and 5-aminolevulinic acid (ALA). The secondary objectives were to compare the two treatments regarding pain, detection of substance P, change in fluorescence intensity from before to 5 h after cream application and adverse events not related to local phototoxicity.

Methods: Thirty-four healthy volunteers were treated by PDT using MAL 160 mg/g cream and ALA cream 20% randomly assigned to treatment areas on the inside of each upper arm. A composite score of local phototoxic events (erythema, edema, hyperpigmentation) was calculated.

Results: The area under the curve (AUC) analysis of composite scores showed a significantly higher AUC for ALA-PDT (P < or =0.0001). ALA- and MAL-PDT showed equivalent local side-effect frequencies, except for a higher frequency of hyperpigmentation after 28 d using ALA-PDT (P=0.006).

Conclusion: MAL- and ALA-PDT are nearly equivalent regarding individual side-effect frequencies, but MAL-PDT has a more favorable phototoxicity pattern as seen by AUC analysis and the lower frequency of long-lasting hyperpigmentation.