Intra-lesional chemotherapy (ILC) using 5-fluorouracil (5-FU) for treatment of keloid lesions was first introduced by Fitzpatrick in 1989 . In a survey conducted by the author , only 4.23% of keloid patients reported having received ILC injections for treatment of their keloids. In the United States, and perhaps globally, the most commonly used chemotherapy drug is 5-FU.
In preparing 5-FU for ILC, Fitzpatrick (1999) reported using 50 milligrams (mg) per milliliter (ml) concentration of 5-FU , which is the usual concentration of the undiluted drug in its vial . Although Fitzpatrick capped the total administered dose of 5-FU at 100 mg per treatment session, he did not provide a rationale for choosing this dose or for the concentration of 5-FU used in his experiment. However, this original work might have been the reason behind the common practice of using the undiluted solution of 5-FU, i.e. the highest possible concentration of the drug for intralesional injections. The author has personally interviewed several practitioners who use 5-FU at the highest concentration of 50 mg/ml – straight out of the vial – a practice that is in line with using Kenalog-40 and injecting undiluted triamcinolone into the keloid tissue [4,5].
The author is unaware of any studies to determine the proper dosage of 5-FU for intra-lesional treatment of keloids. Other chemotherapy drugs, such as bleomycin and mitomycin, have also been used in treating keloids with variable results .