Photo Dynamic Therapy During Accutane?

Isotretinoin (past brand named Accutane) will cause some profound drying of your skin as the sebaceous glands have restricted function. Undergoing a fairly aggressive procedure like Photo Dynamic Therapy at the same time could cause a hyper reaction while you are taking this drug.

Guidelines for the use of Accutane like drugs include being careful with UV exposure from any source. Your response while on Accutane to PDT could be quite severe and markedly unpleasant with some potential for scars if your skin burns excessively.

One or the other, but not both at the same time. I would not recommend this combination.

I would recommend you avoid any light-based energy devices while on Accutane including photodynamic therapy whether it is activated by blue/red light, IPL or laser. One effect of Accutane is to make you considerably more photosensitive (sensitive to light). If the intention of the photodynamic therapy is to treat your acne, it is not necessary if you are going to be on accutane.
Good luck.