In a previous study, it was shown that the phototoxic effects of 5-aminolevulinic acid, a well-established photosensitizer used in photodynamic therapy, were heightened in the endometrial epithelium when a P-gp inhibitor (verapamil) was present [85], thereby signifying the influence of P-gp on drug exposure in endometriosis and suggesting that modifying drug transporters could be an effective strategy for enhancing drug delivery [85]. Here, PGP is linked to endometriosis.