Morphine gel 0.3% does not relieve pain during topical photodynamic therapy: a randomized, double-blind, placebo-controlled study.

There is a demand for pain relief during photodynamic therapy. We therefore investigated the efficacy and side-effects of topical morphine gel 0.3% for pain relief during topical photodynamic therapy in a randomized, double-blind, placebo-controlled study. The study involved 28 patients with actinic keratoses or basal cell carcinomas. Each patient was treated with photodynamic therapy after superficial curettage of 2 treatment areas that were randomized to morphine gel or placebo gel. The gels were applied 15 min before illumination. Pain was assessed pre-illumination, during, and immediately after illumination, using a numeric rating scale. Skin redness was determined by reflectance spectrophotometry and the size of the treated area by protoporphyrin IX fluorescence. There were no differences between the areas according to accumulation of protoporphyrin IX (p =0.34), size of fluorescence areas (p =0.84), or skin redness (p =0.95). There was no significant pain relief of topical morphine gel compared with placebo gel (p >0.23). This negative result suggests that opioid receptors may not be involved in the pain induced by photodynamic therapy.