Bowel Prep Update 2006 

The industry is working hard to formulate more patient-friendly routes with an increased efficacy of bowel cleanliness. EndoNurse highlights today’s hot bowel prep products and the current research that describes the efficacy and side effects of such products. 

Bowel preparation is a necessary evil for thousands of patients each year. Unfortunately, the process also has been proven to be the No. 1 deterrent of adherence to recommended colonoscopy screenings.¹ The more likely complaints are the volume of the solutions that must be ingested; other complaints involve taste and accompanying side effects such as bloating and nausea. The bottom line remains however, that the effectiveness of the bowel prep must be the greatest consideration. 

In a recent attempt to assess which bowel preparation agent is most effective, researchers conducted a meta-analysis by pulling studies that were published between January 1990 and July 2005.² The meta-analysis discovered that sodium phosphate (NaP) was more effective in bowel cleansing than polyethylene glycol (PEG) or sodium picosulphate (SPS). Patients showed more difficulty completing PEG than NaP and SPS. All three were comparable in terms of adverse events, with PEG resulting in slightly more adverse events than SPS. NaP resulted in more asymptomatic hypokalemia and hyperphosphatemia than the other two, leaving the researchers to conclude that “the biochemical changes associated with a small-volume preparation like NaP, albeit largely asymptomatic, mandate caution in patients with cardiovascular or renal impairment.” 

The risk factors mentioned and other underlying conditions can predispose certain patient groups to serious side effects from certain bowel prep formulations. For example, calcium and magnesium changes are more pronounced in patients who receive phosphate salts for bowel preparation.³ Moreover, acute renal failure and nephrocalcinosis (kidney calcification), although the occurrence is rare, also can develop after NaP administration.⁴ It is believed this occurs as a component of a systemic syndrome associated with severe hyperphosphatemia and hypocalcemia. 

“Taking a detailed history and, when in doubt, using a PEG solution, will safeguard against inappropriate administration of NaP,” according to researchers who conducted a study to investigate the safety of NaP vs. PEG, without first being informed of the patient’s medical history.⁵ Eleven patients in the study were identified with a theoretical contraindication for NaP, nine of whom should have been discovered by taking a detailed clinical history. The study highlighted the importance of thorough pre-operative screening. In addition, six study participants receiving NaP showed a doubling of serum phosphate levels, and hypokalemia was found in four. 

Mark vB Cleveland, PhD, vice president of medical affairs with Braintree Laboratories Inc., maker of HalfLytely®, GoLYTELY®, and NuLYTELY®, says electrolyte derangements resulting from phosphate absorption from the sodium phosphate cleanouts have been recognized for many years. He says there have been numerous reports of transient renal failure resulting from the hyperphosphatemia, hypocalcemia, and hypokalemia which occur with phosphate overload. “Thus, labeling for these products recommends that patient electrolytes and renal status be checked before use of the preparation,” he points out. 

It should be noted that in the last study mentioned⁵, patient tolerance to NaP was better overall and those on the NaP regimen completed the preparation more often. Another study comparing NaP to a standard four liter PEG also found a higher completion rate (84.2 percent vs. 27.5 percent) within the NaP group.⁶ The researchers noted NaP was also more cost-effective. 

Doug Bettenhausen, PharmD, executive director of medical affairs for Salix Pharmaceuticals Inc., says Salix is launching a new NaP product this month (June). OsmoPrep™ Tablets is a smaller, easier to swallow, microcrystalline cellulose (MCC)-free sodium phosphate tablet formulation, approved in March by the U.S Food and Drug Administration (FDA) for marketing in the U.S. The standard dosing regimen for OsmoPrep contains 20 percent less sodium phosphate than its predecessors. In recent clinical trials of the 32-tablet regimen, OsmoPrep was associated with fewer overall adverse events and was associated with a smaller increase in serum phosphorous levels.⁷ 

“Obviously the biggest deterrent from preps is the huge volume that must be consumed,” Bettenhausen recognizes. Because this is a tablet regimen, he says there have been better compliance and patient preference rates. “It causes less side effects than the PEG products,” he says, adding, “They actually have a PEG in them but it’s not PEG 3350, it’s PEG 8000, which is a different tablet binder that gives them a waxy feel so they go down easier.” The tablets also are lactoseand gluten free.

Salix also is working on a two-liter PEG product that contains ascorbic acid (vitamin C). The formula, named MoviPrep, is expected to launch later this year. “Ascorbic acid, at high doses (5 grams, but 10 grams is used in the MoviPrep product) has a cathartic effect,” Bettenhausen explains. “In other words, it tends to bring water into the GI tract and helps to clean out the GI tract. So the combination of the PEG and the ascorbic acid in MoviPrep actually gives you a very nice prep.” Bettenhausen adds that it also helps from a taste standpoint because the natural flavoring of vitamin C gives MoviPrep a better taste. 

Allyson Mortati, global product manager of patient preparation systems with E-Z-EM™ Inc., describes her company’s NutraPrep® product as a “nutritionally sound diet” for the day prior to the procedure. NutraPrep provides three complete meals plus beverages and snacks, which can be particularly useful for patients who have difficulty fasting, such as frail or elderly patients, or pediatric patients. “This represents a significant improvement over clear liquid diets that patients are generally limited to for the day prior to procedure,” she adds. In addition, E-Z-EM also offers its LoSo Prep™ — a low liquid volume, “pleasant tasting” bowel preparation consisting of magnesium citrate, bisacodyl tablets, and bisacodyl suppository. 

A clinical study using both NutraPrep and LoSo Prep prior to colonoscopy found that the combination achieved higher ratings for bowel preparation and patient preference than a clear liquid diet and use of a double-dose NaP.⁸ 

Katie Brahm, associate product manager with Schwarz Pharma, manufacturer and distributor of TriLyte™ with Flavor Packs, says there are side effects associated with bowel cleansing agents. “As with all PEG lavages, nausea, abdominal fullness, and bloating are the most common adverse reactions,” she says. 

Perhaps the most pronounced side effect of any bowel prep is the accompanying chance of dehydration. Bettenhausen says that the average person will lose three liters of fluid during bowel preparation. “Proper hydration is key in the use of these products,” he affirms. 

According to Brahm, TriLyte with Flavor Packs when reconstituted to 4 liters, is an isosmotic solution and large volumes may be administered without significant changes in fluid or electrolyte balance. “The osmotic activity of polyethylene glycol and the electrolyte concentration result in virtually no net absorption or excretion of ions or water,” she says. 

Bettenhausen says Salix’s OsmoPrep product has the hydration factor built into the delivery of the tablets because the patient must drink a clear liquid to swallow the 32-tablet regimen. As for Salix’s MoviPrep, Bettenhausen says the label will reflect special instructions related to hydration. “MoviPrep is a two-liter prep. As I already mentioned, you lose three liters, so you certainly are going to see on our label the importance of hydrating before, during, and after taking this prep (by taking in fluids in addition to the two liters of the prep),” he says. 

Bettenhausen makes a good point on the importance of proper hydration in all phases of bowel prep usage. “Now, the recommendation is the patient must be hydrated before they even begin the purgative,” he shares. “So not only following the use of the prep, but during and before the preparation, proper hydration is very important.” 

Cleveland warns against drinking excessive quantities of water during or after the preparation however, “as this can result in hyponatremia,” he says. “The gastrointestinal lavage products (Braintree’s GoLYTELY, NuLYTELY, and HalfLytely) were formulated to preserve patient electrolyte and water balance,” he adds. He further warns, “Patients should adhere to the preparation instructions in the product labeling. The addition or mixing of the product with drink mixes or other beverages should be discouraged as this can result in an imbalance of electrolytes if these products contain salts or sugars. In addition, added sugars may result in the generation of potentially explosive gasses by gut flora. Be sure to complete the preparation as instructed,” he offers. 

It is very important that clinicians educate patients on the importance of adhering to the instructions of bowel preps. Brahm says education is extremely important throughout the process, “Beginning with the physician being educated on all of the bowel prep options, following with nurses/schedulers’ education on increasing patient awareness,” she asserts. “If the patient does not adhere to the healthcare provider’s direction, there is a possibility that the colon may not be clean and the prep procedure may need to be repeated, possibly entailing another colonoscopy.” She also adds that patients be advised about the fact that any oral medication taken within one hour of the start of administration of TriLyte with Flavor Packs may be flushed from the GI tract and not absorbed. Brahm mentions that Schwarz Pharma has developed a Web site, www.yourcolonhealth.com, where healthcare providers and patients may obtain additional information. 

Mortati adds that E-Z-EM is also focused on patient education. E-Z-EM has patient education literature and information programs available to doctor offices to help patients understand the importance of bowel preparation. “We think it is extremely important to a successful bowel preparation,” she explains. “The patient’s full understanding and cooperation is critical to making sure that the bowel prep is optimal. On this point,” she continues, “the NutraPrep pre-procedure meal kit can simplify the process of explaining the dietary requirements to a patient. Instead of having to field questions about what foods are and are not allowed, the office staff simply explains that the patient can eat whatever they would like out of the kit, and nothing else.” 

For references, visit www.endonurse.com  

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