Azathioprine and UC
YS wrote in to the blog recently with questions regarding immunomodulators for UC.
The immunomodulators, azathioprine and 6-mercaptopurine (6-MP), are medications which have been widely used in both Crohn's disease and UC for many years. The medications work by inhibiting metabolism of nucleic acids and cell growth. Indications for starting immunomodulator therapy include disease refractory to maximal treatment with oral 5-ASA medications, topical 5-ASA and steroids, and high doses of prednisone, in those patients who are no so ill as to require hospitalization.
Immunomodulator therapy is often started at a dose of 25 to 50mg daily. The maximal doses of immunomodulators are often quoted as: 1.5mg/kg/day for 6-MP and 2.5mg/mg/day for azathioprine. Many physicians will perform a blood test to measure the level of an enzyme called TPMT that is required to metabolize the medications. Knowing this value can help physicians adjust a patient's dosage. It takes 6-8 weeks for these medications to build-up to a therapeutic level in the body. As such, a person must be stable enough to be able to wait through this time for the medications to take effect. Tests are available to monitor the level of the medication in a person's blood to help guide future dosing.
Potential side effects of immunomodulators include nausea, vomiting, bone marrow suppression (a low white blood cell count), pancreatitis, elevation of liver enzymes, and allergic reactions. Patients starting on these medicines are initially required to have blood tests performed every 2-4 weeks to survey for side effects. If lab tests remain stable for 2 months, they are then checked every 3-4 months for the duration of medication use.