lois,

Thanks for your question.  Unlike the statin medications used to lower Cholesterol and metabolized through the liver, Zetia works through the bowel.  One of the listed side effects of zetia is diarrhea.  There is a possibility your system may have adjusted to the zetia and now that you have discontinued this medication, you are experiencing the opposite.  It might take a few weeks for your bowels to readjust.

This is just a possibility, which brings us back to a cardinal rule.  If a patient experiences any change in bowel habits that lasts more than a couple of weeks, it needs to be evaluated by a physician.  Unless there is another reason for you to develop impactions, you should see your doctor soon for his examination and opinion.  There are several factors to consider such as your age, family history, medication, other underlying medical conditions, and your physical findings. 

Best wishes.

Martin Cane, M.D.