Laxative Preparation for Colonoscopy
Note: The Colonoscopy Chronicles attempts to provide information that is as accurate as possible. It is not intended as medical advice. You should consult your personal physician regarding your own medical condition.
In order to do a colonoscopy properly, the colon has to be completely clear of stool. This means that prior to the procedure, the patient has to take some sort of laxative preparation to cleanse the colon. As a general rule, this is the part of the entire process of colonoscopy that patients hate the most! I can’t tell you how many times patients have told me,”The procedure was easy, it’s just that prep that was tough”.
There are a huge variety of laxative preparations that have been used over the years. Each has its pros and cons-and none are perfect. Unfortunately, many of them can cause cramps and nausea, and they can be just downright nasty tasting. Some seem less effective than others and can leave some residual stool in the colon, which limits the effectiveness of the test. Others can lead to dehydration and electrolyte (sodium, potassium) abnormalities that can be dangerous. Some have even been associated with severe kidney damage.
I am not going to give you a comprehensive review of every colonoscopy prep available. But I will speak from personal experience about the ones I have prescribed in the in the past and the ones I currently use.
There are a number of PEG preps on the market. The common denominator here is that the active ingredient is PEG(polyethylene glycol). PEG is a molecule that helps draw water into the lining of the intestine, which then flushes the intestinal contents out. These laxative preps also contain extra sodium and potassium to replace that which is often lost in this process. The PEG solutions are appealing for their safety, and effectiveness. They are of particular importance in patients with kidney failure or heart failure. Other types of preps may cause fluid and electrolyte disturbance that are particularly harmful in these conditions, whereas the PEG preps have much less chance of doing so. The downside of these solutions is that they taste lousy. They have a somewhat salty, sweet taste that can get on your nerves, especially when you have to drink such a large amount of it. Even though there are flavoring packets available for many of the solutions, they are still not particularly pleasant.
Despite these imperfections, I believe that PEG preps are generally the best currently available, and I recommend them for almost all my patients undergoing colonoscopy.
I’ll briefly review some of the PEG solutions available. The original PEG preps consisted of a four liter solution(almost 1 gallon). There are several of these that are still available, and are in common use today. These include: Golytely, Colyte, and NuLytely. The main advantage of the 4 liter solutions is price:they are about half the price of the 2 liter solutions. These cost in the $25-30 range.
Due to the fact that many people have trouble consuming 4 liters of a PEG solution over 4 hours, lower volume PEG solutions were developed. These include HalfLytely and MoviPrep. The HalfLytley involved taking two laxative pills followed by 2 liters of PEG solution. The MoviPrep consists of a one liter solution of PEG which is repeated as few hours later. The main disadvantage of these preps is the pricing, which is in the $50-60 range.
I have prescribed almost all of the above preps. I think that they are all basically safe and effective. Since the 2 liter solutions are easier to take, I favor them if the patient is willing and able to afford the additional cost. Of the two liter preps, I favor MoviPrep, since the dulcolax tablets in the HalfLytely can cause additional cramping. However, in fairness to the manufacturers of HalfLytley, at the time I was prescribing it, the recommended dose included 4 dulcolax tabs. This was recently changed to two, and I have not yet tried this new formulation-which was designed to reduce the crampiness.
Other Common Laxative Preps
While I generally do not use these preps, I will briefly discuss them.
Fleets Phosphosoda-This is a solution that has been around for many years, and is a fairly effective laxative. It became popular as a lower volume alternative to the 4 liter PEG solutions. Patients complained of its bad taste, and it could cause the usual cramps and nausea that the other preps caused. In 2006 the Food and Drug Administration reported that 21 cases of a rare form of kidney failure had been associated with this prep. Many physicians stopped using this form of prep following this report.
Pill Prep-The idea of replacing drinking up to a gallon of lousy tasting fluid with downing a few pills is very appealing. Unfortunately, there are several reasons why I don’t favor pill preps: 1) You need to take a large number of pills (32) 2)I find the cleanout to be less satisfactory than the PEG preps 3)The pills are made of essentially the same chemical contained in the Fleets Phosphosoda, and therefore may have the same potential for kidney damage
Odds and Ends
There are a million and one other ways to cleanse the colon, and I won’t get into every single one that is used. I will mention that your physician may recommend an enema(which is basically a small volume of liquid that is inserted into the rectum-designed to clear out the last few inches of the colon)-in addition to the laxatives you need to drink.
· Whatever prep you and your physician agree to use, make sure you understand the directions your physician gives you, and follow them carefully.
· Often the solution is more palatable if you chill it. Taking a bite or two of lemon sorbet in between drinking the PEG solution made it a little more tolerable.
· Remember, the better your cleanout, the better your physician can see inside your colon. This increases the chance of detecting abnormalities like polyps. So be an active partner in the process.
Remember, after you’ve finished your laxative cleanout-the worst is over!!
Next installment: Types of anesthesia used in colonoscopy
Sunday, December 2, 2007
Laxative Preparation for Colonoscopy
Posted by Doctor Mike at 9:01 PM