Increased urination on lactulose?

[Kellynorrrris]

My vet just prescribed Pimento liquid lactulose twice daily to help with his regularity. He’s only taken one dose so far (last night) and he’s gone pee 3 times between overnight and this morning, no poops. I saw a side effect of the drug is dehydration. Peeing this often is not normal for Pimento, so I’m not sure if the increased urination is a negative side effect? I know it helps water to be absorbed by the digestive system so maybe this is why he’s peeing more. Just want to know if anyone has experienced this as an adverse side effect. I’ll keep an eye on him and call the vet in the mean time. Thank you!

 

[white shadow]

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Hi Kelly !

FWIW, lactulose for cats is 'old medicine'. Nowadays, folks more commonly use Miralax. (Lactulose is 'yucky' for cats.)

Here's a little on each from a reputable site (which should be required reading for anyone with cats, IMO): Feline Constipation.org - Osmotic Laxatives.

Perhaps you can speak to the Vet about switching.
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[di and bob]

Yes, I use Miralax, 1/4 tsp. mixed in an egg yolk or a little bit of food. Lactulose is very sweet, we gave much of it in nursing homes mixed in orange juice. It draws liquid into the system, thus causing more water to be eliminated and softening any present stool. More water through urination too, which can cause dehydration. If given too often it can prolong constipation because dehydration causes constipation! So offer plenty of water and maybe talk to your vet about miralax to be used too.

 

[Kellynorrrris]

Yes, I use Miralax, 1/4 tsp. mixed in an egg yolk or a little bit of food. Lactulose is very sweet, we gave much of it in nursing homes mixed in orange juice. It draws liquid into the system, thus causing more water to be eliminated and softening any present stool. More water through urination too, which can cause dehydration. If given too often it can prolong constipation because dehydration causes constipation! So offer plenty of water and maybe talk to your vet about miralax to be used too.

If the lactulose can cause him to pee more, I’m concerned/confused about how it’s supposed to help the constipation? If he’s just peeing it out, furthering the dehydration, how will this help him poop?

 

[di and bob]

No, it draws moisture in all along his sysyem, including the bowels. Drawing it into his bowels softens the stool that is in there. His urinary system is tied into the digestive system, as we drink water it goes to many systems, being filtered by the kidneys and sent to where it is to go. It does not go directly to the bowels.

 

[BlackCatOp]

If the lactulose can cause him to pee more, I’m concerned/confused about how it’s supposed to help the constipation? If he’s just peeing it out, furthering the dehydration, how will this help him poop?

My understanding is most of the lactulose remains unabsorbed until it reaches the cat's colon where the lactulose is broken down into smaller molecules by gut bacteria. The smaller molecules increase osmotic pressure within the colon and cause water to be drawn into the colon - thus softening stool.

While most (>90%) of the lactulose remains unabsorbed, a small percent is absorbed within the small intestine of the cat. The lactoluse is not metabolized and is excreted unchanged by the kidneys. I would fathom that this process is leading to an osmotic diuresis which is causing the increased urination but I do not find anything to support this thought. (However, this is the same idea why diabetic cats pee more - high glucose is acting as an osmotic diuretic)

I agree that asking your vet is a good idea! Sorry Pimento is constipated!