Best Laxatives For A Colonoscopy: Quick And Effective Options

Colonoscopies are a simple medical procedure that examines the inside of your colon for abnormalities or signs of disease. To complete this procedure, your colon must be cleaned out through a thorough bowel prep regimen. There are several different types of colonoscopy prep regimens available today, including prescription and over-the-counter options. The best laxative for a colonoscopy is one that is recommended by a medical professional and is suitable for the patient's needs.

Polyethylene glycol (PEG)-based laxatives

PEG-based laxatives are typically in powder form and are mixed with large volumes of water. They may include electrolytes or directions to be consumed with a sports drink to prevent dehydration caused by fluid loss when the colon empties. They usually come in different flavors, with some people preferring sulfate-free options as they taste less salty. Brands that offer PEG-based laxatives include GoLYTELY, MiraLAX, MoviPrep, NuLYTELY, and TriLyte.

PEG-based laxatives typically require drinking high volumes of formula (up to 4 liters). This can be challenging for some people to tolerate and complete. To address this issue, some variations of the standard formula have been developed, including flavor options and lower-volume formulas. For example, MiraLAX and Halflytely combine a smaller dose of PEG with another laxative, bisacodyl, reducing the volume of formula from 4 liters to 2. However, the 2 liters must be consumed within the same hour.

The time it takes for a PEG-based laxative to take effect is typically between one and three hours. It is recommended to start the bowel prep the afternoon or evening before the colonoscopy. For a morning colonoscopy, a "split" prep is often offered, where patients take half the prep the night before and the other half on the morning of the procedure. Studies have shown that split preps are better tolerated and allow for a clearer view of the colon.

Saline-based laxatives

Pros of Saline-Based Laxatives

Sodium phosphate bowel preps may be easier for some people to swallow, and they are equally effective when taken as directed. For those who find it difficult to complete a PEG bowel prep, a NaP formula can help ensure a successful colonoscopy.

Cons of Saline-Based Laxatives

The salts in NaP formulas can irritate your intestinal mucosa if you have an inflammatory gastrointestinal disease. They are also not the best option for those at risk of complications from fluid-electrolyte shifts, such as those with kidney, liver, or heart disease.

Saline-Based Laxative Brands

• SUPREP®
• Clenpiq®
• Sutab® (tablet form)
• OsmoPrep
• Visicol

How to Take Saline-Based Laxatives

If you are doing a split-dose prep, the night before the procedure, pour one bottle of SUPREP, for example, into a mixing container and then fill it with water to the 16-ounce line. Mix and drink it, and then drink an additional 32 ounces of water over the next hour. Repeat this process the next morning, 10 to 12 hours after the evening dose and three to four hours before the procedure.

Pills for Prep

The pill route for colonoscopy prep involves taking 24 pills in total. However, many doctors recommend patients take 12 pills the night before the procedure and 12 more the morning of the procedure if they are doing a split prep. Plenty of water is needed to go with those pills. For example, if you are using Sutab, take one pill with a sip of water every 1 to 2 minutes (16 ounces of water total) until you've taken 12 pills. Then, drink an additional 32 ounces of water over the course of an hour. Repeat these steps on the morning of the procedure.

Osmotic laxatives

Polyethylene glycol (PEG) is the most commonly prescribed osmotic laxative for colonoscopy prep. It is a large molecule that can't be absorbed through your colon, causing a hyperosmotic effect. PEG formulas are typically in powder form and are designed to be mixed with large volumes of water. They may include electrolytes and/or include directions to be taken with a sports drink.

PEG-based colonoscopy prep drinks include GoLYTELY, NuLYTELY, MiraLAX, Halflytely, and GaviLyte. These formulas are highly effective for colonoscopy prep and are considered a gentler choice for people with irritable bowel syndrome (IBS). However, they often require drinking high volumes of formula (up to 4 litres), which can be challenging for some people.

To address this issue, some variations of the standard PEG formula have been developed, such as NuLYTELY and TriLyte, which are sulfate-free and have a less salty taste. MiraLAX and Halflytely combine a smaller dose of PEG with another laxative, bisacodyl, reducing the overall volume of formula to 2 litres. However, this 2-litre dose must be consumed within the same hour.

In addition to PEG, osmotic laxatives such as magnesium citrate and bisacodyl are also used in colonoscopy prep. These are known as dual therapy or combination formulas, which can be more effective for some people. However, stimulant laxatives like bisacodyl are associated with adverse outcomes, including bloating, cramps, and abdominal discomfort, and are contraindicated for certain patient populations. Therefore, PEG-only regimens are generally recommended as the first-line therapy for colonoscopy prep.

Pills for prep

The first thing to know about taking pills for your colonoscopy prep is that it will be a lot of pills: 24, to be exact. However, as with liquid laxatives, many doctors recommend patients take 12 pills the night before the procedure and 12 more the morning of the procedure if they are doing a split dose.

Plenty of water is needed to go with those pills. For example, if you are using Sutab, the night before the procedure, you take one pill with a sip of water every 1 to 2 minutes (16 ounces of water total) until you’ve taken 12 pills. You then drink an additional 32 ounces of water over the course of an hour. These steps are repeated on the morning of the procedure.

While some doctor’s offices have a preferred method of prep, many work with their patients based on their needs, or some offices might offer patients several choices.

It’s also important to note that the salts from NaP (sodium phosphate) preps can irritate your intestinal mucosa if you have an inflammatory gastrointestinal disease. NaP formulas also might not be the best option for those at risk of complications from fluid-electrolyte shifts, as well as for those who have certain pre-existing conditions or who take certain medications.

“For example, someone with chronic kidney disease might have electrolyte imbalances that would mean one prep is better than another, and your doctor should go over all of that with you,” says Jeremy Matloff, MD, a Yale Medicine gastroenterologist. “Or some people prefer the pills because the taste of the liquid prep is a limiting factor for them.”

Sometimes, insurance coverage can be an issue with the pills or other specific preps. But they typically cost less than $50.

“All preps have various nuances, but if we can give patients easier options that fit their individual preferences, it increases the chances they’ll have a successful colonoscopy,” Dr Matloff says. “And that will lead to more lives saved.”

Over-the-counter laxatives

Colonoscopy is a simple medical procedure that examines the inside of your colon for abnormalities or signs of disease. To complete this procedure, your colon must be cleaned out through a thorough bowel prep regimen. There are several over-the-counter laxatives available for colonoscopy preparation.

Dulcolax

Dulcolax is an over-the-counter laxative that can be purchased without a prescription. It comes in the form of tablets that contain bisacodyl, which helps to stimulate the bowels. The recommended dosage is four tablets taken the evening before the procedure, followed by two tablets taken between 3 and 5 pm on the day before the colonoscopy. It is important to drink at least eight glasses of water throughout the day when taking Dulcolax.

MiraLAX

MiraLAX is a popular over-the-counter laxative that comes in a variety of flavours. It is made up of polyethylene glycol and electrolytes, and patients typically drink a total of four litres of the solution over several hours. It is important to start the MiraLAX preparation between 2 pm and 4 pm on the day before the colonoscopy. It should be mixed with Gatorade or a similar drink, and one 8-ounce glass of the solution should be drunk every 15 minutes until it is gone.

Magnesium Citrate

Magnesium citrate is another over-the-counter option for colonoscopy preparation. It is available in 10-ounce bottles and should not be purchased in red (cherry) flavour. The preparation involves drinking two bottles of magnesium citrate—one the evening before the procedure and one on the day of the procedure, five hours before the scheduled arrival time. It is important to drink an 8-ounce glass of water with each bottle of magnesium citrate.

General Instructions for Over-the-Counter Laxatives

When using over-the-counter laxatives for colonoscopy preparation, it is important to follow a clear liquid diet on the day before the procedure and until midnight prior to the colonoscopy. This includes clear liquids such as water, chicken broth, apple juice, ginger ale, tea, and black coffee. Solid foods and milk or milk products should be avoided. Additionally, it is recommended to stop taking iron supplements and vitamin E one week before the procedure, and to discontinue ibuprofen, Motrin, Advil, and similar medications three days prior.

Frequently asked questions