5-aminosalicylic acid (5-ASA) and thiopurines (
azathioprine and
mercaptopurine) are the most common drugs used as a maintenance treatment for
ulcerative colitis. A considerable proportion of these patients develop
corticosteroid dependency, and thiopurines are the standard treatment in this scenario. Dual prescriptions of both thiopurines and 5-ASA are common practice in
steroid-dependent
ulcerative colitis, in an attempt to optimize the efficacy of
therapy. On the one hand, the potential protective role of 5-ASA against
colorectal cancer argues in favour of prescription of both medications. The possible synergism between the two drugs, because of the inhibition of
thiopurine methyltransferase (TPMT)
enzyme activity by 5-ASA, has been postulated as another justification for dual prescription. However, existing evidence does not support that this combined strategy is superior to monotherapy with thiopurines. On the other hand, in patients showing prolonged disease remission, the possibility of discontinuing maintenance treatment can be considered on an individualized basis. The high frequency of relapses after
thiopurine withdrawal should always be taken into account, but the potential adverse effects of the medication also need to be considered. A properly indicated treatment with thiopurines may need to be continued for life in many patients.