How Long Does MiraLax Last in the Body?

MiraLax, containing the active ingredient polyethylene glycol (PEG) 3350, is an over-the-counter (OTC) orally administered medication approved by the Food and Drug Administration (FDA) for treating occasional constipation. 

Miralax belongs to the class of osmotic laxatives, medications used as a short-term treatment for constipation. PEG 3350 is also available under various brand names, such as GaviLax, HealthyLax, and SmoothLax.

MiraLax is an effective treatment for temporary constipation. You can buy it OTC if dietary and lifestyle changes do not relieve the symptoms.

MiraLax is safe as it will stay for a few hours in your system and produce therapeutic effects within a few days.

Miralax typically takes effect within one to three days, and most of the Miralax dose is eliminated from the body within 48 to 72 hours after consumption.

This article will provide an in-depth analysis of MiraLax, explaining need-to-know information regarding the safe use of this medication.

Understanding Constipation

Constipation is a condition of fewer than three bowel movements a week. It is characterized by various symptoms, including hard stools, difficulty passing stools, incomplete evacuation, abdominal discomfort, and bloating.

Various causes of constipation include diet, inadequate fluid intake, genetic makeup, medications, advanced age, a low-fiber diet, a lack of exercise, and abdominal or pelvic surgery.

General treatment options for constipation include getting enough fiber, drinking sufficient fluids, and exercising.

However, if your constipation does not improve, you can try an OTC laxative or ask your healthcare provider for a prescription laxative.

Laxatives are drugs used to manage constipation. They increase the frequency and ease of passing bowel movements by increasing the stool volume and stimulating the large intestinal muscle by increasing the intestinal pressure.

Some different types of laxatives include:

• Stool softeners, laxatives that increase the amount of water and fat your stool absorbs
• Lubricant laxatives, laxatives that make the stool slippery and, therefore, easier to pass by lubricating the intestinal walls
• Osmotic laxatives, laxatives that draw water into the colon, which can help to hydrate stool and speed up emptying time
• Bulk-forming laxatives, laxatives that work by increasing the weight of stool, therefore stimulating your bowel

Sometimes, constipation leads to chronic symptoms called chronic constipation and may need long-term treatment plans or surgical procedures.

Constipation is a common condition affecting all ages and populations in the United States. Nearly 16 out of 100 adults have symptoms of constipation.

It is more prevalent in older people. About 33 out of 100 adults aged 60 and above have symptoms of constipation.

What Is Miralax?

MiraLax is FDA-approved for the short-term treatment of occasional (irregular) constipation in adults 18 and older.

MiraLax, an osmotic laxative, works by preventing the reabsorption of water, which causes water retention in the stool. As a result, it makes the stool softer and easier to pass and increases the number of bowel movements.

PEG (not specifically PEG 3350) has many pharmaceutical and other uses. PEG can be used in cosmetic products as surfactants (an active ingredient in cleaning detergents), emulsifiers (food additives that mix substances that typically separate when combined), and skin conditioners.

As a medication, PEG is a part of the laxative drug class.

Additionally, PEG 3350 is used off-label with other substances for cleansing the colon (part of the intestine) in preparation for colonoscopy in adults.

Variation of MiraLax

MiraLax only comes as a powder for reconstitution into an oral solution (adding the medication into a liquid and letting it dissolve) and is unavailable in tablet or capsule forms.

Bottles of MiraLax powder come in the following doses:

• 10 doses
• 20 doses
• 30 doses
• Twin packs containing 34 doses each

MiraLax is also sold in single-dose packets containing 17 grams (g) of powder.

PEG 3350 is also available in powder form in various generic formulations.

How Long Does MiraLax Last in the Body?

Research is lacking on the time it takes for MiraLax's active ingredient to leave the body.

However, according to studies, peak levels of PEG-3350 in the bloodstream occurred two to four hours after taking a 17 g dose. MiraLax starts producing bowel movements within one to three days.

These studies confirmed that PEG-3350 is absorbed in a small quantity in the gastrointestinal (GI) tract, which includes the stomach and intestines and is rapidly excreted from the body via the feces.

A typical Miralax dose is eliminated 48 to 72 hours after consumption.

The effects of MiraLax only last for a day or so. It works as it travels through your digestive system. Its effects gradually decrease as it is passed out of your body with the stool.

Therefore, it is essential to take it daily to benefit from it.

Dosage Overview

The recommended dose of MiraLax is 17 g in adults 18 and older.

It comes in bottles or packets containing powder for reconstitution.

To prepare MiraLax:

• Fill the powder in a measuring cup, marked at a 17 g dose, or pour a packet into a container containing 4 to 8 ounces of water, juice, soda, coffee, tea, or other beverages.
• Stir to dissolve, and drink immediately.
• Use once each day.

Ask your healthcare provider if MiraLax is safe for children younger than the recommended age.

Additionally, know that MiraLax may be habit-forming (potentially addictive).

Consequently, do not take a larger dose of MiraLax more often or take it longer than instructed.

Safely Taking MiraLax

Most laxatives are taken with meals or at bedtime. Before getting approval from your healthcare provider, do not take more than one laxative or medicine, including mineral oil.

Eat a well-balanced diet of fiber, fresh fruits, and vegetables, drink plenty of water, and exercise regularly.

If you are constipated, eat all meals and avoid processed or fast foods, such as doughnuts, sausage, fast-food burgers, potato chips, and French fries.

Contact your healthcare provider if you have not had a bowel movement in three days, have a bloated stomach, or have blood in your stool. 

Store Miralax at room temperature (between 68-77 degrees F). Also, keep MiraLax and other drugs locked away and out of reach of children and pets.

Side Effects & Safety

Like all drugs, MiraLax carries the potential for adverse effects. Therefore, while using MiraLax or caring for a loved one using the medication, watch closely for the emergence of side effects.

If side effects persist or worsen over time, contact your healthcare provider immediately for guidance. You may be advised to stop using MiraLax or any other laxative.

Because MiraLax can be habit-forming, monitor yourself or a loved one for signs of addiction, including loss of appetite, bloating, rapid weight loss, and muscle cramps.

Common Side Effects

Some common side effects associated with the use of MiraLax include:

• Nausea
• Bloating
• Cramping
• Gas

Severe Side Effects

Call your healthcare provider immediately if you develop urticaria (hives), other allergic symptoms, or diarrhea.

Who Shouldn't Take Miralax?

MiraLax should not be used in people with the following preexisting conditions:

• Known or suspected bowel obstruction
• Appendicitis (inflammation of the appendix)
• Nausea, bloating, or abdominal pain that gets worse
• Inflamed bowel disease (IBD), such as Crohn's disease or ulcerative colitis (UC)
• Hypersensitivity to polyethylene glycol or any other component of the MiraLax formulation

If you are pregnant or breastfeeding, contact your healthcare provider before taking MiraLax, as this medication may negatively affect breastfeeding or childbirth.

How Effective Is MiraLax?

Various studies show that oral administration of 17 g of MiraLax once daily for a week is effective, safe, and well-tolerated in people with occasional constipation.

Other commonly used OTC laxatives are Metamucil, Citrucel, and Dulcolax.

Summary

Constipation is a disorder of the GI tract. It is characterized by a low frequency of stools and difficult stool passage, sometimes with pain and stiffness.

There are various causes, including a low-fiber diet, inadequate water intake, medicine side effects, genetics or hormone imbalance, etc.

Changing what you eat and drink may soften the stools and make them easier to pass, but medicine is sometimes needed. 

One such laxative is MiraLax (PEG 3350), an OTC powder reconstituted before use. It’s classified as an osmotic laxative for the short-term treatment of occasional constipation.

For most people, taking MiraLAX will cause a bowel movement within one to three days. MiraLax stays in the body for nearly a day or two to produce therapeutic effects.

Therefore, repetitive dosing is required for a few days to achieve an effective result.