The reason why you can't or shouldn't stay at 20mg is because the long term side effects of prednisone are irrereversible and damaging. Long term use is considered any dose for over 4 months. The problem with pred use is that the damage from prednisone usually shows up after the patient stops taking it. If you are having problems getting off pred successfully and have been on it for more than 4 months, it's time to have a talk with your GI about the next options.
dx proctitis in 1987
dx UC in 1991, was stable until 1998
1998 started prednisone, asacol, pentasa, nortriptylene, ativan, 6MP, rowasa enemas and suppositories, hydrocortisone enemas, tried the SCD diet, being a vegetarian, omega 3s, flax, pranic healing, yoga, acupuncture, probiotics
2000 lost all my B-12 stores and became anemic
2001 opted for j-pouch surgery- now living life med-free