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Updated: May 20, 2026
An In Vitro Approach to Photodynamic Therapy
Published on: August 17, 2018
The relation between methyl aminolevulinate concentration and inflammation after photodynamic therapy in healthy
Susanne Fabricius1, Catharina Margrethe Lerche, Peter Alshede Philipsen
1Department of Dermatology, Odense University Hospital, Denmark.
Abstract:
Inflammation and pain are well known adverse-effects in photodynamic therapy (PDT). There is currently a tendency towards introducing lower concentrations of the photosensitizer than used in the standard treatment for various indications. The aim of this study was to investigate whether reduced concentrations of methyl aminolevulinate (MAL) can reduce inflammation (erythema) during PDT treatment. We measured the formation of protoporphyrin IX (PpIX) using fluorescence and monitored both erythema and pain during and after PDT treatment with conventional 16% MAL and threee reduced concentrations of 2, 0.75, and 0.25% in twenty-four healthy volunteers. We found that lowering the MAL concentration reduced PpIX fluorescence and erythema after PDT treatment. There was a strong correlation (R(2) = 0.70) between the PpIX fluorescence and erythema after treatment. A further increase in erythema after PDT was dependent on pre-treatment skin erythema. PpIX fluorescence could explain 70% of the increase in erythema (P < 0.0005). Pain and post-treatment hyperpigmentation can be reduced but not eliminated by limiting the MAL concentration. An efficacy study of PDT with these three reduced concentrations has not been performed.
Insights
Reducing methyl aminolevulinate (MAL) concentration in photodynamic therapy (PDT) lowers protoporphyrin IX (PpIX) fluorescence and erythema. This approach may reduce pain and hyperpigmentation, but efficacy requires further study.
Area of Science:
- Photodynamic Therapy
- Dermatology
- Biochemistry
Background:
- Photodynamic therapy (PDT) commonly causes inflammation and pain.
- Lowering photosensitizer concentrations is a trend in PDT treatment.
- Methyl aminolevulinate (MAL) is a widely used photosensitizer.
Purpose of the Study:
- To investigate if reduced concentrations of methyl aminolevulinate (MAL) can mitigate inflammation (erythema) during PDT.
- To assess the correlation between protoporphyrin IX (PpIX) formation and treatment-induced erythema and pain.
Main Methods:
- Twenty-four healthy volunteers received PDT with conventional 16% MAL and reduced concentrations (2%, 0.75%, 0.25%).
- Protoporphyrin IX (PpIX) formation was measured using fluorescence.
- Erythema and pain were monitored during and after PDT treatment.
Main Results:
- Reduced MAL concentrations led to decreased PpIX fluorescence and post-treatment erythema.
- A strong correlation (R(2) = 0.70) was observed between PpIX fluorescence and erythema.
- PpIX fluorescence accounted for 70% of the increase in erythema (P < 0.0005).
- Pain and hyperpigmentation were reduced but not eliminated with lower MAL concentrations.
Conclusions:
- Lowering MAL concentration in PDT effectively reduces PpIX formation and associated erythema.
- While pain and hyperpigmentation may be lessened, they are not entirely eliminated.
- Further efficacy studies are needed to evaluate PDT with these reduced MAL concentrations.
