This information is approved and/or reviewed by U-M Health System providers but it is not a tool for self-diagnosis or a substitute for medical treatment. You should speak to your physician or make an appointment to be seen if you have questions or concerns about this information or your medical condition.| Complete disclaimer

Phospho-soda Oral Laxative Preparation: OsmoPrep

If you have severe heart or liver disease or any kidney disease, you should NOT use a phospho-soda laxative preparation. Also, if you take medicines for blood pressure or heart disease (ACE inhibitors or angiotensin receptor blockers), diuretics (water pills) or certain arthritis medicines (NSAIDs) you should not use this type of preparation unless instructed to do so by your health care provider.
OsmoPrep oral bowel prep contains tablets that are available by prescription only. Start the prep the day before your colonoscopy. Plan to be near a bathroom for the rest of the evening. Your bowels may begin to move in about 30–60 minutes. Feelings of nausea and bloating are common and resolve with time. An A&D type ointment applied to the rectal area can help with any irritation. The goal is for your stool to be clear or light yellow water.

Phospho-soda tablets (OsmoPrep)

You will take a total of 32 tablets, divided into two sets of tablets, beginning the day before your colonoscopy. You will need a prescription for OsmoPrep. 

_____ Begin taking the first set of 20 tablets between 12 noon and 6 PM, the day before your colonoscopy. Take a dose of 4 tablets every fifteen (15) minutes (for example, 4 tablets at 4 PM, 4 at 4:15 PM, 4 at 4:30 PM, etc). It will take one (1) hour to take the 20 tablets. Take each dose of 4 tablets with at least 8 ounces of clear liquid.

_____ The second set of 12 tablets should be taken 10–16 hours later and at least 4 hours before the colonoscopy. Again, take a dose of 4 tablets every fifteen (15) minutes. It will take thirty (30) minutes to take the second set of 12 tablets. Take each dose of 4 tablets with at least 8 ounces of clear liquid.

You should take other clear liquids between doses of the OsmoPrep laxative. Drinking at least a gallon of clear liquids will improve the quality of bowel cleansing. See the colonoscopy general instructions for a list of allowed liquids.

Information provided by the University of Michigan Health System, Internal Medicine Gastroenterology Clinics and Medical Procedures Unit. October 2012.