The treatment of problematic scars or the excessive buildup of scar tissue underneath the skin after surgery can be a very difficult problem. The most common treatment has been the use of intralesional injections using Kenalog. (triamcinolone acetonide) While this has proven effective for many scar problems, it does not always work and is associated with certain side effects, most commonly fat or skin atrophy. Some patients have been described as having resistance to Kenalog, although this probably has more to do with the quality of the scar than it does with some systemic drug resistance.
For those scar problems that do not respond to Kenalog treatment, there is an alternative injectable drug using5-flourouracil. 5-fluorouracil (5-FU) is an antimetabolic cytostatic drug that inhibits DNA formation. In laboratory cultures, 5-FU barely reduces collagen reduction in normal fibroblasts, but produces a drastic reduction in collagen formation in altered fibroblasts. It also seems to counteract the capacity of growth factor TGF-1 to stimulate collagen production.
There have been multiple recommended mixtures for 5-FU scar injections. One method uses a mixture of 0.9 ml of 5-FU 50 mg/ml and 0.1 ml triamcinolone 10 mg/ml per ml. Another mixture is composed of1cc of 50 mg of 5-FUand 10 mg of lidocaine 1%. These mixtures are used primarily because 5-FU injections can be painful. The pain can be alleviated by these dilution measures or by giving a local anesthetic block prior to 5-FU injections.No more than 3 mls are injected in a single session in order to prevent potential systemic effects derived from the use of 5-FU. Although 150mgs (3 mls) is far below the dose generally administered in cancer treatments. (thousands of mgs)
The treatment schedule is more frequent than that used for Kenalog, being done on a weekly basis over the first four weeks, and then every two weeks thereafter. On an average 5 to 10 injection sessions are needed to achieve the best result. Side effects seen with 5-FU injections are pain and stinging and bruising at the injection site.
The results of intralesional injection with low concentrations of a solution of 5-FU and steroids has been shown over the past decade to be effective for reducing the production of collagen and aiding in the reorganization of scar fibers. 5-FU inhibits DNA synthesis and inhibits fibroblast proliferation inducing regression of keloids and hypertrophic scars. Intralesional 5-FU is associated with pain which is reduced by the addition of triamcinoloneor local anesthesia. To be most effective,5-FU injections need to be done when collagen and scar formation is actively being produced.
Dr. Barry Eppley