Schering-Plough has made their polyethylene glycol (PEG) laxative Miralax® available over-the-counter in the same strength as the original prescription version. Taken once a day, Miralax works by drawing water into the bowel.
A 2005 review of medical literature found good evidence to support the use of PEG laxatives to relieve constipation, assigning a Grade A. The only other agent with a Grade A rating, tegaserod or Zelnorm® has recently been removed from the market. Grade B or moderate evidence was found for psyllium, and lactulose. The reviewers found very little data on the use of commonly used laxatives including milk of magnesia, senna, bisacodyl, and stool softeners.
Writing in the American Journal of Gastroenterology, Ramkumar and Rao concluded,
There is good evidence to support the use of PEG, tegaserod, lactulose, and psyllium. Surprisingly, there is a paucity of trials for many commonly used agents. These aspects should be considered when designing trials comparing new agents with traditional therapies because their use may not be well validated.
Cancer patients often face constipation from chemotherapy and from the need for opiates to treat pain.