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  • PDT combines the use of a photosensitizer, a light source within the absorption spectrum of the photosensitizer, and molecular oxygen which, when stimulated, destroys a specific target tissue.

  • PDT is a common procedure, and is used for the treatment of actinic keratoses, superficial nonmelanoma skin cancers, acne, and photodamage, among other indications.

image Beginner Tips

  • While both ALA and MAL are effective photosensitizers for PDT, currently only ALA is available in the United States.

  • The ideal time from ALA application to activation ranges broadly, and while the FDA-approved indication calls for ALA application the day before activation, in practice many clinicians wait only 1 hour prior to light activation.

image Expert Tips

  • Daylight PDT is becoming increasingly popular due to both convenience and comfort, though further studies are needed to better quantify the amount of exposure needed for different geographic locations and different times of the year.

  • Both blue LED and IPL have been used with significant success for activation.

image Don’t Forget!

  • Sun protection, including indirect sun protection, is absolutely critical to avoid overactivating the photosensitizer.

  • Consider HSV prophylaxis in all patients with a history of HSV in the treated area.

image Pitfalls and Cautions

  • Stripping may occur due to uneven light or photosensitizer application, and can be treated by retreating the entire area.

  • In the United States, PDT is generally not used for the treatment of skin cancers as monotherapy.

image Patient Education Points

  • Patients should be warned that they will need to not only practice religious sun protection, but that they will also have significant erythema for at least several days after the procedure. Work and social schedules should be planned accordingly.

image Billing Pearls

  • Insurance coverage for PDT is variable, and generally the only indication for coverage in the United States is nonhypertrophic actinic keratoses on the face and scalp.

  • ALA is currently only available from a single manufacturer in the United States and in single-use stick form.

  • Since physicians bill directly for the photosensitizing drug, extreme caution is warranted in assuring the amount of coverage available for a given insurance company, as the physician risks spending more on purchasing the medication than they will be reimbursed.


Photodynamic therapy (PDT) was first performed over 3,000 years ago in ancient Egypt, when plant substances in concert with sun exposure were found to produce a skin reaction. PDT represents a chemical reaction, where a photosensitizing chemical (photosensitizer) is activated by a light source in target tissue. The chemical reaction produces singlet oxygen and other cytotoxic free radicals. PDT combines the use of a photosensitizer, a light source within the absorption spectrum of the photosensitizer, and molecular oxygen which, when stimulated, will destroy a specific target tissue.



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