How Do Bowel Preps Work?

Bowel preps are a class of medications used to clean out the intestines before a certain bowel exam procedure (colonoscopy). A colonoscopy is a type of imaging study that involves inserting a thin, flexible tube called a colonoscope into the body through the anus to examine the colon (large intestine) and rectum. The main purpose of a colonoscopy is to investigate symptoms in the colon and colorectal area, such as abdominal pain, constipation, passing blood with bowel movements, and persistent diarrhea and to remove polyps or tissue for a biopsy at the same time.

During a colonoscopy, it is possible to identify growths and other intestinal problems including:

• Noncancerous polyps
• Colon cancers
• Bleeding
• Areas of inflammation

Bowel preps are administered as a powder that is mixed with lukewarm water and taken orally. It is usually taken in the evening before and/or on the morning of the procedure. Your doctor will tell you when you should begin taking this medication and whether you should take all of the medications at one time or take it in two separate doses. You may not eat any solid foods or drink milk before and during the treatment. You should only have clear liquids before the procedure and will be asked to drink a certain amount of clear liquids to decrease the chance of being dehydrated as your colon is emptied. 

Bowel preps work in the following ways:

• They are osmotic laxatives that work by drawing large amounts of water into the colon.
• They stimulate watery bowel movements, removing stool, food particles, and any other residues that may be clinging to the tissue surfaces.
• Clearing stools from the intestines helps the doctor to better examine the intestines during the colonoscopy procedure.
• In addition, they contain minerals to replace electrolytes that are passed from the body in the stools.

Bowel preps are used for the following:

• Before procedures such as:
  • Colonoscopy in adults
  • Barium enema (a test in which the colon is filled with a fluid and then X-rays are taken)
• Constipation
   

Common side effects include:

• Diarrhea
• Headache
• Nausea
• Vomiting
• Dry mouth
• Tiredness
• Muscle pain
• Abdominal pain
• Dyspepsia (a persistent or recurrent pain or discomfort in the upper abdomen)
• Bloating
• Flatulence

Other rare side effects include:

• Severe diarrhea
• Decreased urination
• Irregular heartbeats
• Leg cramps
• Severe abdominal pain
• Rectal bleeding
• Hypersensitivity
  • Rash/urticaria
  • Pruritis (itching)
  • Dyspnea (shortness of breath)
  • Chest and throat tightness
  • Fever
  • Angioedema (swelling beneath your skin)
  • Dizziness

Information contained herein is not intended to cover all possible side effects, precautions, warnings, drug interactions, allergic reactions, or adverse effects. Check with your doctor or pharmacist to make sure these drugs do not cause any harm when you take them along with other medicines. Never stop taking your medication and never change your dose or frequency without consulting your doctor.

Generic and brand names of bowel preps include:

• Clenpiq
• CoLav
• CoLyte
• GaviLyte-C
• GaviLyte-G
• GaviLyte-N
• Glycolax
• GoEvac
• GoLytely
• MiraLax
• MoviPrep
• NuLYTELY
• Plenvu
• Polyethylene glycol & electrolytes
• Polyethylene glycol electrolyte soln
• Polyethylene glycol powder
• Polyethylene glycol/electrolytes/sodium ascorbate/ascorbic acid
• Prepopik
• Sodium picosulfate/magnesium oxide/anhydrous citric acid
• Sodium sulfate/magnesium sulfate/potassium chloride
• Sodium sulfate/potassium sulfate/magnesium sulfate
• Sodium sulfate/potassium sulfate/magnesium sulfate/polyethylene glycol
• Suclear
• Suprep
• Sutab
• TriLyte