Medical Therapy Part I: 5-ASA
Once a new diagnosis of UC is made there are several available treatment options ranging from no treatment at all to various medical therapies to surgical resection of the colon.
The mainstay of medical treatment for mild to moderate UC is the 5-aminosalicylic acid (5ASA) class of medications, including sulfasalazine, mesalamine and balsalazide. While all of these medications have similar efficacy, sulfasalazine has a higher rate of dose dependent side effects including nausea, vomiting, and headache. Sulfasalazine and balsalazide are only available in pill form for oral delivery, while mesalamine is available in pill form, as well as suppository and enema formulations. Side effects of mesalamine include diarrhea and rare kidney toxicity.
The 5ASA’s are anti-inflammatory drugs that block several important immune response pathways. They seem to work both locally, by direct effects on the intestinal cells, and systemically, once absorbed in to the circulation. While chemically similar to acetylsalicylic acid (aspirin), 5ASA has different effects on the gastrointestinal tract and immune system. Most notably, aspirin exacerbates UC in some cases.
Several clinical trials have shown that there is a dose dependent effect of the 5ASA’s. A high dose is more effective at inducing remission, while a lower dose is effective at maintaining remission. Distal UC, affecting the left colon (descending, sigmoid, or rectum) may be treated with 5ASA in suppository or enema formulations. Enemas reach the entire left colon, but suppositories only treat the rectum. These rectal formulations may be effective on their own, but response is even better when paired with oral 5ASA therapy.
The potential role of 5ASA as a chemopreventive (see posting 8/23) against colon cancer in UC makes its long term use a compelling, though unproven, consideration.