Bowel Preps 101

Full update September 2017

Patients’ proper use of bowel preps is a key part of a successful colonoscopy and other bowel imaging procedures (e.g., sigmoidoscopies, etc). The bowel must be properly cleaned in order for a colonoscopy to detect issues. Bowel preps clean mucus and feces out of the gut so that any problems in the bowel, such as colon polyps or cancer, can be seen during the colonoscopy.

Bowel preps are notoriously difficult for patients to use. Many patients say that the most uncomfortable part of a colonoscopy is actually the bowel prep beforehand! In fact, about one in four patients don’t get good bowel prep before a colonoscopy. There are likely a number of reasons for this, including the poor taste of some of the preps and the large amounts of fluid that patients have to drink.

Help promote proper use of bowel prep regimens by understanding the differences between bowel preps and how they are used.

MoviPrep #1, Mix each dose with 1 L H2O prior to use. Take 1 dose p.m.  prior to colonoscopy. Take 2nd dose a.m. of colonoscopy. Finish 2nd dose and additional clear fluids at least 2 hrs before  procedure..

Mary Anderson, a 64-year-old female patient, comes in to the pharmacy with an Rx for MoviPrep. The sig says that she should mix one dose and take it the evening before her colonoscopy. Then on the morning of the colonoscopy, she is to mix another dose and finish it, along with additional needed liquids, at least two hours before the colonoscopy. Mrs. Anderson tells you that her colonoscopy is scheduled for next Tuesday, and that she also has an information sheet from her healthcare provider with more instructions to follow before her colonoscopy. She seems a little anxious about getting this Rx filled. You let the pharmacist know that Mrs. Anderson may have some questions.

What are the different kinds of bowel preps?

There are several different kinds of bowel preps. They include powders that must be mixed with water, such as CoLyte and GoLytely. There are also oral tablets, such as OsmoPrep (U.S.). The type of bowel prep a patient receives will depend on factors such as his or her age, medical history, cost, preference, and other meds the patient is taking.

Some bowel preps are OTC. Miralax (U.S.) and Lax-A-Day, Pegalax, and Restoralax (Canada) are polyethylene glycol (PEG) products that are available OTC. PEG products are typically powders that must be mixed with a liquid before administration. Patients who take PEG products ingest large amounts of fluid that flush out the bowel. Electrolyte concentrations can be decreased when patients lose large amounts of fluid through the bowel. Unlike other PEG products that require a prescription (Rx), OTC PEG products do not have replacement electrolytes, such as potassium and sodium. This means that patients who use OTC PEG products might be at a higher risk of dehydration than those who use the Rx PEG products with electrolytes.

The instructions for using OTC PEG for bowel prep can be complicated. Also, since the OTC PEGs are marketed as laxatives for constipation, the instructions for their use as bowel preps will not be on the product label. So if you get an Rx for OTC PEG, still process it as an Rx, even if it isn’t covered by the insurance. This way, you can put the prescriber’s instructions on the Rx label, and also be sure that the patient gets the correct product.

Magnesium citrate (Citroma [U.S.], Citro-Mag [Canada], etc) oral solution is a bowel cleanser that can be found OTC. Magnesium citrate works by pulling water from the body into the bowel to help clean it out. It’s less expensive than most other bowel preps, but it’s often combined with other bowel prep meds. It’s not as safe or effective (on its own) as other bowel preps and for these reasons, is less frequently used. If a bowel prep calls for magnesium citrate, make sure to choose the lemon flavor. Cherry and grape flavors may have dyes that can make it hard to see the details of the gastrointestinal (GI) tract during the procedure. And these dyes may make it look like there’s blood in the GI tract.

Other meds for bowel prep are Rx only. In the U.S., sodium phosphate tablets are available as the Rx drug OsmoPrep. Like magnesium citrate, these pull water from the body into the bowel to help clean it out. They require less fluid intake than other bowel regimens, making them better tolerated for some patients.

One downside of sodium phosphate tablets is that they can cause damage to the kidneys. OsmoPrep even has a boxed warning about this. This risk is most concerning in certain patients, such as those with kidney disease, the elderly, and in those who take blood pressure meds such as ACE inhibitors (captopril, enalapril, etc), ARBs (losartan, valsartan, etc), or some diuretics (furosemide, hydrochlorothiazide, etc). Another downside to this product is that it is significantly more expensive than other bowel preps.

The combination of sodium sulfate, potassium sulfate, and magnesium sulfate (Suprep [U.S.], etc) works similar to sodium phosphate and magnesium citrate. It comes as a solution that must be mixed with more liquid before it is taken by the patient. This product also requires less fluid intake than other bowel preps, so it may be better tolerated, but it has a higher price tag.

Prepopik (U.S.) or Pico-Salax (Canada) is a combination of sodium picosulfate, magnesium oxide, and citric acid. These products work similarly to magnesium citrate. However, they come as a powder that needs to be mixed with water, and not as a liquid like magnesium citrate. Like OsmoPrep and Suprep, these products require less fluid intake than other bowel preps, but may be more expensive.

PEG products with electrolytes (e.g., CoLyte, GoLytely, MoviPrep) are also Rx in the U.S. (See below concerning regulatory status of Canadian products.) As mentioned, they are less likely to cause dehydration than plain PEG (i.e., without electrolytes) since PEG products with electrolytes provide extra potassium and sodium.

The downside of PEG products with electrolytes is that patients must drink very large volumes of fluid, up to four liters. Plus, they have a very salty taste from the sodium and potassium. Some of the products, such as CoLyte and GoLytely, may have a rotten egg smell because they contain sulfates. NuLytely (U.S.) and TriLyte (U.S.) are sulfate-free and may taste better to some patients. A product that requires the patient to drink less volume, such as MoviPrep which calls for half the volume, might be better tolerated.

Many bowel preps may be given as divided dose or "split-dose" regimens. Part of the dose is taken the night before the colonoscopy and the rest is taken the morning of the procedure. This can make the bowel prep more effective and better tolerated. Often, PEG products are given this way.

Note that in Canada, PEG products with electrolytes and Pico-Salax are classified as “ethical” products. These don’t technically require a prescription, but they are typically kept behind the counter in pharmacies, not on pharmacy shelves for general access.

As you are filling Mrs. Anderson’s Rx, the pharmacist takes the time to speak with her. They look over her instruction sheet together. The pharmacist emphasizes the importance of drinking all of the MoviPrep and taking it exactly as the Rx label says. Her colonoscopy is scheduled for 11 AM, so he tells her that she must finish the second dose of MoviPrep and any additional clear fluids before 9 AM on the morning of her colonoscopy.

Are there ways to improve tolerability of oral solutions for bowel prep?

To improve the taste of PEG products with electrolytes, patients may prefer a flavoring. Many of the products come with optional flavor packets. Citrus flavor works best to mask the salty taste. One trick is to rub a fresh lime or lemon on the tongue. Or, patients can add lemon juice or a sugar-free flavoring like Crystal Light to the solution. However, anything that is red or purple in color should never be added to the PEG solution. As previously mentioned, these dyes could cause problems with the procedure since they can make it hard to see details of the GI tract during the procedure.

PEG products are best reconstituted with lukewarm water which helps dissolve the powder. However, refrigerating the solution prior to use might help with the taste. (Refrigerating magnesium citrate solutions can also improve the taste.) Using a straw to drink the solution can help bypass taste buds and prevent nausea.

As previously mentioned, many prescribers will tell patients to divide the dose of the bowel regimen. Patients may have less nausea and vomiting when part of the dose is taken the night before the colonoscopy and the rest the morning of the procedure. Most regimens can be taken this way.

You hear Mrs. Anderson tell the pharmacist that she is very glad she doesn’t have to drink a huge jug of fluid all at once. Her sister recently used GoLytely and had a hard time getting it all down. The pharmacist tells Mrs. Anderson that if she ever has to use this product in the future, he can help her out with some tricks for making it easier. She asks the pharmacist if she will need to buy any other meds for her bowel prep (her sister had to use bisacodyl tablets and suppositories) and the pharmacist confirms that she does not.

Are there any special considerations for dispensing bowel preps?

Be on the lookout for mix-ups with drug names, especially the PEG products. CoLyte and GoLytely can look and sound similar. Suprep and MoviPrep can sound similar. And CoLyte and TriLyte or Miralax and MoviPrep can look similar.

The different PEG products can have the same or similar ingredients. However, despite their similarities, PEG products can’t always be substituted for one another. In the U.S., there are generics for some (e.g., CoLyte, GoLytely, NuLytely, etc) and not for others (e.g., MoviPrep). NuLytely and TriLyte (U.S.) are equivalent and can be substituted for one another according to the U.S. Orange Book. Since Miralax and the generic four-liter PEG products with electrolytes are less expensive than other brand products, the pharmacist may want to help facilitate a switch to save the patient money. Check with the pharmacist and follow your state laws for substitution.

Instructions for bowel prep can be long. When receiving electronic prescriptions (eRxs) for bowel preps, make sure to look at the “special instructions” and “notes” sections. Expect prescribers to utilize these areas to fit in all the details.

For example, watch for prescriptions that mention using bisacodyl (Dulcolax) along with the bowel prep. This is a stimulant laxative that can help increase the movement of contents out of the bowels. Bisacodyl is often added to Rx PEG products when patients are only taking half of the volume. Using half the volume (two liters instead of four) of a generic Rx PEG product plus bisacodyl has been found to be as effective and less expensive than other low-volume PEG products, such as MoviPrep. Make sure patients know if they need bisacodyl and help them find this product over the counter if it isn’t being processed as an Rx. Include instructions for bisacodyl use on the Rx label.

Are there any special labeling requirements for bowel preps?

Be sure to include complete and detailed directions for use on the prescription label. If the directions don’t fit, work with the pharmacist to make sure the patient gets a complete copy of all the directions from the prescription. We have a chart, Comparison of Bowel Preps (U.S. subscribers; Canadian subscribers), which you can refer to for more details on typical instructions for various bowel preps.

When labeling the box or container, avoid covering up any preprinted instructions. These give pictures or extra tips on proper dosing. Also, avoid covering dosing lines on the containers. The “fill to” line should be clear so the patient knows the correct amount of water to add.

Include a "use by" auxiliary label on prescriptions for PEG products. Most will need to be used within 24 to 48 hours after they are reconstituted.

Also in the U.S., make sure to dispense a MedGuide with outpatient prescriptions for Rx PEG products, Suprep, Prepopik, and OsmoPrep. Medication guides include warnings for patients about fluid and electrolyte loss with these meds.

You have a tough time getting all of the instructions for use of the MoviPrep on the Rx label. There isn’t enough room for all of the details. You talk to the pharmacist and he instructs you to include on the Rx label “Take one dose the evening before and one dose the morning of the procedure as directed in the additional instruction sheet.” You know that there are instructions for mixing MoviPrep on its box, so you make sure that the Rx label does not cover those instructions. You write out the full instructions on an extra instruction sheet and pass the Rx to the pharmacist for a final check.

What other information is important for patients who are using bowel preps?

Pharmacist counseling of these patients is very helpful to reinforce complicated instructions and strategies for helping things go smoothly. Be sure to alert the pharmacist that patients picking up Rxs for bowel preps need counseling. For example, patients need to know that once they start taking meds for bowel prep, they will have very frequent bowel movements. In fact, a bowel movement can be expected within the first hour after starting the bowel prep. It’s best for these patients to stay home so they have immediate access to their bathroom, as well as privacy.

Bowel prep with meds usually starts one day before the procedure. Meds will typically be combined with a clear liquid diet. In general, a clear liquid diet includes bouillon or consommé, plain gelatin, clear soft drinks, sports drinks, popsicles, honey, hard candies, thin juices without pulp, or plain tea or black coffee. Thick beverages such as milk or orange juice that the patient cannot see through should be avoided. Again, anything with red or purple coloring should be avoided as well. A “low residue” diet is often suggested two or more days before the procedure. A low residue diet consists of avoiding high-fiber or difficult to digest foods, such as whole grains, nuts, raw fruits, and raw vegetables. Following these diet recommendations can help improve the effectiveness of bowel preps.

Patients may ask whether or not they should continue to take their regular meds during bowel prep. This is also information that the pharmacist can help with. The answer might depend on the med, the patient’s other conditions, etc. For example, many blood thinners (warfarin, etc) and NSAIDs (ibuprofen, etc) may need to be held for up to a week before the procedure. These meds can increase bleeding risk. Be sure to keep patient profiles up-to-date with both Rx and OTC products the patient is taking.

Patients will experience diarrhea which will be watery and in large volumes. They may also have nausea and bloating. Walking around a bit might help reduce the nausea and bloating. Because the patient will likely make frequent trips to the bathroom, the anus may become irritated by frequent wiping. Applying petroleum jelly between bowel movements and using unscented disposable baby wipes for wiping may help prevent irritation. Help direct patients to these products as needed.

How can I help motivate patients to follow their bowel prep regimens?

There’s a simple explanation for why proper use of bowel preps is important. Screening for colon cancer helps catch cancers early and is proven to save lives. Inadequate bowel prep can lead to something being missed. Check out our CE, The Pharmacy Technician Role in Colon Cancer Screening, for more tips on how to help patients who need to prep for a colonoscopy.

Mrs. Anderson takes some time to shop for extra supplies such as baby wipes, petroleum jelly, and several large bottles of citrus-flavored sports drink. It turns out that since her sister had a colonoscopy recently, she knows what to expect. The pharmacist gave her information to fill in the gaps and helped her make sure that she understood the directions from her healthcare provider correctly. As you are ringing up Mrs. Anderson’s purchases, she says that she really cannot wait until her procedure is over. You tell her to hang in there and that it will all be worth it. After all, colon cancer screening saves lives.

Project Leader in preparation of this technician tutorial (331080): Flora Harp, PharmD, Assistant Editor

Cite this document as follows: Technician Tutorial, Bowel Preps 101. Pharmacist’s Letter/Pharmacy Technician’s Letter. October 2017.

—Please continue for a handy Cheat Sheet about bowel preps—

"Cheat Sheet" – What You Need to Know About Bowel Preps

Why is it important for bowel prep regimens to be followed correctly?

Proper use of bowel prep regimens is key for making sure tests, such as colonoscopies, are successful. Colonoscopies can save lives by detecting cancer. Inadequate bowel prep can lead to something being missed.

How do bowel preps work?

In general, most bowel preps work by causing lots of water to enter the bowel and clean it out.

What are some important considerations with the different kinds of bowel preps?

  • OTC
    • Polyethylene glycol (PEG) without electrolytes (Miralax [U.S.], Lax-A-Day [Canada], etc)
      • Always process Rx’s for OTC PEG as an Rx to include instructions from prescriber
    • Magnesium citrate (Citroma [U.S.], Citro-Mag [Canada], etc)
      • Choose lemon flavor over cherry/grape to avoid dyes that interfere with testing
  • Rx (or Ethical in Canada)
    • PEG with electrolytes (CoLyte, GyLytely, MoviPrep, etc)
      • Downsides: large volumes of fluid need to be consumed (up to 4 liters), very salty taste, rotten egg smell with some sulfate-containing products
      • MoviPrep is a lower-volume option (2 liters), but may be more expensive
        • May see large-volume PEG products ordered with instructions to consume only 2 liters; usually will be used with bisacodyl (stimulant laxative)
    • Sodium phosphate tablets (OsmoPrep [U.S.])
      • Requires less fluid intake than PEG solutions so may be better tolerated
      • Downsides: may cause kidney damage and is expensive
    • Sodium picosulfate, magnesium oxide, citric acid (Prepopik [U.S.], Pico-Salax [Canada])
      • Powder that needs to be mixed with water; lower volume but more expensive
    • Sodium sulfate, potassium sulfate, magnesium sulfate (Suprep [U.S.], etc)
      • Solution that must be mixed with more liquid lower volume but more expensive

How can I help patients be adherent to their bowel regimen?

  • Provide complete and detailed directions on the Rx label
  • When labeling the box or container, do not cover up any preprinted instructions or “fill to” lines
  • Include a “use by” auxiliary label
  • Provide a MedGuide in the U.S. with outpatient Rxs
  • Always refer patients to the pharmacist for counseling

What other information should I know about bowel preps?

  • Bowel preps can be difficult to tolerate due to:
    • Salty taste – citrus flavoring, refrigerating solution prior to use, using a straw to drink the solution, etc, may help
    • Nausea and bloating – walking around may help
    • Vomiting and nausea – taking part of the dose the night before the colonoscopy and the rest the morning of the procedure can help
    • Anal irritation – applying petroleum jelly and using unscented baby wipes can help
  • Bowel prep meds will often be combined with a clear liquid diet
  • Some patients may need to stop some meds before the procedure (e.g., blood thinners)

[October 2017; 331080]

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