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Medically reviewed by, Russell Braun RPH
Miralax also known by its generic name polyethylene glycol (PEG) 3350 is a laxative medication. Relieve of constipation is its primary use. Miralax can be mixed with water or other liquid. It is available in powder form as either individual packets or a bulk jar.
#1 How it works
Miralax is an osmotic laxative, which means it works by drawing water into the intestines. Osmosis, or moving water across a membrane helps add water into the stool which relieves constipation.
The primary ingredient is a polymer of polyethylene glycol 3350 that is too large to be absorbed in the body. Therefore, it remains inside your intestines and promotes the osmosis of water into the colon, which is near the end of the digestive system. Consequently, constipation is relieved as water that is drawn in the stool softens fecal matter so it can be excreted along with the PEG 3350.
#2 How to know if your constipated?
There is no standard number of times that humans should have a bowel movement per day. How frequently a person goes is a result of many factors such as diet, physical activity, fluid consumption and use of certain medications. The normal range is two to three times per week up to two to three times per day.
Constipation ultimately means having fewer bowel movements than is normal for you. It can also arise from small, dry stools that are painful to pass. Either case may require some form of treatment.
#3 Is Miralax the same as polyethylene glycol 3350?
Polyethylene glycol is the active ingredient in Miralax. The product was first sold under the brand name Miralax, but they are the same thing.
#4 Is there a generic available?
Multiple manufacturers make generic versions of Miralax. Polyethylene glycol 3350 is the active ingredient in all of the generic versions. Most pharmacy chains have their own “store generic” which will be much cheaper than brand name Miralax. Therefore, there are numerous generic version for sale.
The table below depicts the price differences for some Miralax products.
#5 Is Miralax an OTC?
Miralax was first approved by the Food and Drug Administration (FDA) only available with a prescription. The manufacturer applied for and was approved to make a prescription to over the counter switch in 2007.
Therefore, Miralax and its generic version(s) polyethylene glycol 3350 are both available for sale Over The Counter (OTC). The FDA felt this product is safe and effective enough to be used by a patient without requiring supervision by a prescriber.
Laxatives can be dangerous if overused!
Frequent laxative use can lead to dependence on the medication to be able to have a bowel movement. Diarrhea resulting from laxative use can cause electrolyte imbalances which could be dangerous.
As a result, the best practice for using over the counter laxatives such as Miralax is to seek help from your doctor or pharmacist if:
- The medication not worked after 7 days of use.
- Diarrhea lasting more than 2 days occurs.
#6 Is there a prescription strength Miralax?
There is no difference in the strength of Miralax you can buy over the counter versus prescription Miralax. In fact, in 2018 several years after Miralax switched to OTC, the FDA required all prescription products to make the switch to OTC. The manufacturers were asked to reapply to sell there drug under an OTC status instead of prescription.
#7 How often can you take Miralax?
Miralax and the generic products come in a powder form. The normal dose is 17 grams, typically a heaping tablespoonful added to a glass of water. The powder should be stirred until the liquid appears clear. It is intended to be used only once time per day, drinking the entire glass of water.
Miralax generally produces a bowel movement in 1 to 3 days. Studies have shown it to be effective in treating short term constipation. You should not take Miralax more frequently than once per day unless directed by a doctor.
#8 Is too much Miralax bad for you?
Miralax can be used for both short term and long term constipation. It is also used as a bowel preparation prior to surgery. In certain cases where quick relief from constipation is required, higher doses have been used. A study published in the American Journal of Gastroenerology found that doses up to 68 grams were safe and effective for relief of constipation within 24 hours. Doses higher than 68 grams seemed to be associated with adverse effects.
#9 Is it bad to take Miralax everyday?
Taking Miralax every day is not recommended even if it does work to relieve constipation. Over time there is a risk of dependence on laxatives to have a bowel movement. This can cause a dangerous cycle of needing the laxative just to be able to have a normal bowel movement.
Diarrhea can also be a concern when taking Miralax everyday. If the diarrhea occurs frequently, it can result in an excessive loss of water and electrolytes. As a result electrolyte imbalances can cause severe or potentially fatal heart problems such as arrhythmias.
Due to Miralax’s effect on the intestines, absorption of food and medication can be affected. Absorption of nutrients from the diet and certain medications can be affected. You should ask your pharmacist if any medications you take could be affected by using Miralax for constipation.
# 11 Lifestyle changes
Constipation is uncomfortable and not something that anyone wants to deal with on an ongoing basis. First of all, there are some basic lifestyle changes that can be made to prevent constipation.
1. Stay hydrated by drinking plenty of water!
Experts recommend drinking 100 ounces of water per day. Many people would have constipation concerns resolved if they followed that simple recommendation.
2. Avoid foods that can worsen constipation.
Milk and dairy products such as cheese are not the only foods that can cause constipation. Fried foods, excess red meat, processed grains and alcohol can all promote constipation as well.
3. Reach for foods that help prevent constipation.
Foods high in fiber are natural laxatives. Fiber absorbs water in the colon and help move the stool along. Examples of high fiber foods include: wheat bran, beans, fresh fruits, vegetables and oats.
A moderate level of activity is going to help your digestive tract to push the food through the system. Your intestines are a very long system for absorbing things we need from the food we eat. Contracting muscles by exercising helps push food through the system.
For much more on how to treat constipation without laxatives, check out the book, Cure Constipation Now. This is a great resource written by Dr. Wes Jones.
#12 Miralax side effects
Miralax has a low likelihood of causing side effects when taken at the 17 gram dose and on an as needed basis. When side effects occur they are usually seen after starting the medication. They may decease over time if taking for a prolonged period.
Common side effects:
- Abdominal cramping
Short term side effects that are more serious:
- Itching, hives or skin rash
- Severe bloating
- Severe abdominal pain
#13 What are the long term side effects of Miralax?
When constipation lasts longer than a few days it is referred to ask chronic constipation. If constipation persists for more than a week, it is a good idea to seek medical attention. Miralax may be prescribed for you to use on a daily basis. In that case here are side effects to look out for with longer term use:
- Black or tarry looking stools
- Blood in the stool
- Feeling weak
- Stomach cramping that doesn’t go away
- Prolonged constipation even if using Miralax
Any of these side effects warrant another conversation with your doctor or pharmacist to confirm next steps in treating the constipation.
#14 Is Miralax habit forming?
The digestive tract is comprised of small intestines and the colon which are responsible for absorbing nutrients from the food we eat and excreting the remainder as waste. The walls of the digestive tract are formed by smooth muscle that contract and relaxe in a rhythmic pattern called peristalsis. This process moves the waste along in the digestive tract until it is ultimately excreted as a bowel movement.
When you take laxatives such as Miralax over an extended period, your digestive tract can become dependent on Miralax to function. Over time, water pulled into your intestines and colon due to Miralax may be the only way to prevent having infrequent, dry and hardened stools.
Dependence on Miralax to have a bowel movement, can be overcome. Ask your doctor how you can be gradually tapered off of Miralax.
So is Miralax really safe long term?
In general, Miralax is a safe and effective treatment for constipation. If constipation is prolonged then dependance on Miralax can arise. A best practice is to seek medical advice if you are still constipated after 7 days of using Miralax.
Constipation can be an issue for young children and long term use in this group is not advised at this time. In cases where pediatricians have no other choice but to use Miralax long term, some neurologic side effects have been seen. This presents as behavioral changes such as tics, anxiety, mood swings or depression.
#15 Who should not use Miralax?
Don’t use Miralax without consulting a doctor when:
- Patient is under 17 years of age.
- Woman is pregnant or may be pregnant.
- Any patient with a bowel obstruction or blockage.
Click here to get Dr. Jason Reed’s exclusive list of medication questions you MUST ask your doctor, for FREE!
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