US Pharm. 2009;34(9):8. 

Silver Spring, MD -- The FDA, the American Medical Association, and other medical organizations are advising patients against splitting tablets unless it is specified in the drug's labeling. According to the FDA, the practice of splitting tablets can be "risky." There is concern that a patient may get confused about the correct dose; equal distribution of medicine in split tablets is questionable; and some tablets are hard to split (due to small size or unusual shape). The FDA further warns that not all pills, such as capsules, time-release drugs, and drugs with a special coating, are safe to split.