Polyethylene Glycol 3350 (MiraLAX): Cat Kidney Disease Glossary

Polyethylene Glycol 3350 (commonly known by the brand name MiraLAX) is an osmotic laxative used to treat constipation. In the Chronic Kidney Disease (CKD) cat, it has largely replaced Lactulose as the first choice for many owners due to its ease of administration.

The "Water Magnet" Mechanism Constipation in CKD is primarily caused by the colon extracting too much water from the stool to compensate for the cat's overall dehydration.

The Action: PEG 3350 is a large molecule that the body cannot absorb. It sits in the intestine and acts like a sponge, holding onto water molecules.
The Result: By retaining water in the digestive tract, it keeps the stool soft and bulky, stimulating the colon to move it along naturally without the cramping associated with stimulant laxatives.

Palatability: The "Invisible" Advantage The single biggest advantage of MiraLAX over Lactulose is compliance.

Taste and Texture: It is a tasteless, odorless white powder. When mixed with wet food or water, it dissolves completely and disappears.
Compliance: Unlike Lactulose (which is a sticky, sickly sweet syrup that many cats fight), most cats will eat food treated with MiraLAX without ever knowing it is there. This reduces stress for both the cat and the owner.

Dosing "To Effect" There is no "one size fits all" dose for MiraLAX; it is dosed based on results.

The Goal: The objective is to achieve a stool consistency often described as "soft serve ice cream" or a well formed but moist log.
The Strategy: Owners typically start with a small dose (e.g., 1/8 to 1/4 teaspoon) mixed into food twice daily. If the stool remains hard, the dose is increased in tiny increments every few days. If the stool becomes too loose, the dose is reduced.

Safety Profile

Dehydration Risk: Because this drug works by pulling water from the body's reserves into the gut, it is vital that the cat is well hydrated. It works best in conjunction with Subcutaneous Fluids. If you give a high dose of laxatives to a severely dehydrated cat without adding fluids, you can worsen their condition.
Safe for Diabetics: Unlike Lactulose, PEG 3350 is not a sugar and has zero impact on blood glucose levels, making it the preferred choice for diabetic CKD cats.

Disclaimer: This content is for educational purposes only and does not constitute veterinary medical advice. Always consult with your primary care veterinarian or a veterinary internal medicine specialist regarding your cat’s specific condition.

The "Water Magnet" Mechanism Constipation in CKD is primarily caused by the colon extracting too much water from the stool to compensate for the cat's overall dehydration.

The Action: PEG 3350 is a large molecule that the body cannot absorb. It sits in the intestine and acts like a sponge, holding onto water molecules.
The Result: By retaining water in the digestive tract, it keeps the stool soft and bulky, stimulating the colon to move it along naturally without the cramping associated with stimulant laxatives.

Palatability: The "Invisible" Advantage The single biggest advantage of MiraLAX over Lactulose is compliance.

Taste and Texture: It is a tasteless, odorless white powder. When mixed with wet food or water, it dissolves completely and disappears.
Compliance: Unlike Lactulose (which is a sticky, sickly sweet syrup that many cats fight), most cats will eat food treated with MiraLAX without ever knowing it is there. This reduces stress for both the cat and the owner.

Dosing "To Effect" There is no "one size fits all" dose for MiraLAX; it is dosed based on results.

The Goal: The objective is to achieve a stool consistency often described as "soft serve ice cream" or a well formed but moist log.
The Strategy: Owners typically start with a small dose (e.g., 1/8 to 1/4 teaspoon) mixed into food twice daily. If the stool remains hard, the dose is increased in tiny increments every few days. If the stool becomes too loose, the dose is reduced.

Safety Profile

Dehydration Risk: Because this drug works by pulling water from the body's reserves into the gut, it is vital that the cat is well hydrated. It works best in conjunction with Subcutaneous Fluids. If you give a high dose of laxatives to a severely dehydrated cat without adding fluids, you can worsen their condition.
Safe for Diabetics: Unlike Lactulose, PEG 3350 is not a sugar and has zero impact on blood glucose levels, making it the preferred choice for diabetic CKD cats.