Section : Conference Notes

Practical Photodynamic Therapy (PDT) made simple (For Professionals)


  • PDT= photosensitizer + light + oxygen
  • It was discovered in early 1900’s by a medical student (the professor claimed it first as his own !)
  • Its action is through the generation of a singlet oxygen by using drugs and light.
  • Porphyrin sensitizer* + light + porphyrin thus generates an excited porphyrin molecule who passes the energy to oxygen. Singlet oxygen is the consequence of this.
  • Singlet oxygen has the follwing actions:
  1. induces necrosis
  2. induces apoptosis
  3. kills microbes

Important to understand: Porphyrin are huge molecules (unable to penetrate intact skin) whereas ALA (and methyl-ALA) is small. ALA combines with a porphyrin to generate protoporphyrin 9 (PPIX which is photosensitizing).

*ALA= aminolevulinic acid, Methy-ALA=methyl-aminolevulinic acid


1. Administer photosensitizer
2. Wait
3. Apply light

1. Administer photosensitizer (Photosensitizers: ALA or methyl-ALA).

  • ALA:
  1. open application
  2. easier to apply.
  • Methyl-ALA:
  1. occluded application
  2. easier to see.
  1. Off label preparation:
  1. 20% ALA in a solution, lotion or cream.
  2. Prepare it fresh as not stable

A patch is being developed (Szelmies et al, BJD 2010)

2. Wait

  • One hour up to overnight.
  • Lots of variability
  • Photoprotection: just using sunscreens is NOT enough.

Tip: Show lesion to patient with Wood’s lamp as it fluoresces !

3. Apply light

  • Non-laser sources:
  1. sunlight
  2. incandescent light
  3. arc lamp
  4. LED lamp
  5. Intense Pulsed Light (IPL)
  6. Fluorescent light (FDA-approved):
    1. blue lamp: application time 16 minutes (10J/cm2)
    2. red: application time 9minutes (27J/cm2)

Red lamp goes deeper than blue lamp. Blue light is superficial and is only adequate for conditions such as Actinic Keratosis

  • Laser sources:
  1. tunable dye
  2. diode
  • Pain management: probably the most important thing
  1. pre-op education
  2. dedicated PDT staff
  3. verbal reinforcement and reassuraance
  4. Actions to do:
    1. ice
    2. water spritz
    3. fans
    4. cold air
    5. interruption of treatment

Remark: PPIX photobleaches: the red fluorescence is visible on Wood’s lamp. It fades after light exposure. An hour later, the fluorescence comes back (because New PPIX is generated).
In the pipeline: Studies in Scandinavia show that natural daylight would be a solution. It is less pianful as light is shone over a longer time (an hour and a half).
Do not forget: Warn the patient of strong reaction (erythema) which can last up to a week after the treatment.


  • FDA approved:
  1. Actinic Keratosis (AK) treated with the following methods:
  2. ALA + blue fluorescent light
  3. Methyl-ALA + red light
  • Off-label uses:
  1. Cancerous:
    1. Non-Melanoma Skin Cancer (not FDA approved in the US):
    2. Superficial BCC (Basal Cell Carcinoma)
    3. Bowen’s Disease
  2. Genodermatosis (Gorlin’s syndrome)
  3. Prevention of AK (Apola et al, BJD 2010)
  1. Non oncologic:
    1. Psoriasis plaques (Bissonette et al, JID 2002) : it works but it is limited by extreme pain.
    2. Acne Vulgaris: it works but it depends on the tolerance to pain
    3. Hair removal (Grossman et al, Lasers Surg Med 1995): it depends on the tolerance to pain; further studies are still needed to show efficacy.
    4. Photorejuventation
  • Potential indications:
  1. Herpes Virus (Stender et al, Lancet 1995)
  2. Antibiotic resistance
  3. Warts (and genital warts)
  4. Onychomycosis
  5. Leishmaniasis

Studies done for portwine stains (intraveinous systemic administraion; Chinese study)



Dr Christophe Hsu – dermatologist. Geneva, Switzerland

Source of Information: Liu H. Update on Photodynamic Therapy. 71st Annual Meeting of the AAD (American Academy of Dermatology) – Miami, Florida, United States of America (USA)

Category : La photothérapie photodynamique (PDT): un guide pratique - Modifie le 03.2.2013Category : Practical Photodynamic Therapy (PDT) made simple - Modifie le 03.2.2013