altered p-gp function has also been linked to inflammatory bowel diseases (ibd); however, due to its ambivalent effects in intestinal inflammation many questions remain so far unanswered. while decreased efflux activity may promote disease susceptibility and drug toxicity, increased efflux activity may confer resistance to therapeutic drugs in ibd. mice deficient in mdr1a develop chronic intestinal inflammation spontaneously, which appears to resemble human ulcerative colitis.