Aluminum Hydroxide Dosing

Aluminum hydroxide is a type of phosphorus binder used for cats with chronic kidney disease. You can read all about aluminum hydroxide, what it does, how it’s used, etc., here. In this page I’ll cover the different dosing options and methods for aluminum hydroxide.

How It Works

Aluminum hydroxide binds to the phosphorus in your kitty’s food and stops them from being able to absorb that phosphorus into their bloodstream. The most important thing to understand about aluminum hydroxide is that it only works if it is in kitty’s stomach at the same time as the food.

In order to bind to phosphorus the aluminum hydroxide molecules need to be split apart so that the aluminum is separate from the hydroxide. Once the aluminum is alone it can stick to phosphorus instead. Aluminum hydroxide breaks apart when it’s mixed with stomach acid. Then, the broken up pieces of aluminum and hydroxide physically mix with the food while it’s sloshing around in the stomach and moving to the intestines.

Once the food is in the intestines and not in acid anymore the aluminum will try to stick to anything it can. When the aluminum is next to pieces of phosphorus from kitty’s food it will stick to that phosphorus. Some of it will be next to hydroxide and go back to its original form, but the rest will bind to the phosphorus in the food.

Once they’re stuck together the aluminum + phosphorus pieces are too big to absorb into the blood and will instead be pooped out.

If you give aluminum hydroxide and your cat has no food in their stomach there will be nothing for the aluminum hydroxide to stick to when it gets to the intestines other than itself.

Dosage Amounts

The amount of aluminum hydroxide to give can be determined in 3 different ways.

  1. Use an amount based on your cat’s current weight and current phosphorus level
    1. There are several different dosing protocols that can be used
    2. Each protocol is explained at http://felinecrf.org/phosphorus_binders.htm#aloh_dosage
  2. Use an amount based on the amount of phosphorus in their food
  3. Use a combination of #1 and #2
    1. Calculate the dose based on phosphorus content in food
    2. Verify that amount fits within the acceptable range for the dosing protocol you and your vet have chosen for #1

Calculate Based on Food

The hardest part of calculating the amount of aluminum hydroxide to use based on phosphorus content in food is finding out how much phosphorus is actually in your food in the first place. From there, you can use a handy calculator to give you the answer.

TIP: When in doubt about the phosphorus content in food I use 2.0% dry matter as the default. Most commercially available cat foods are at or under 2.0% phosphorus, though there are a few that are as high as 3.3%

Important note about the calculator

The calculator sometimes does not change the result when update any of the numbers. To force it to update the answer, change the “portion fed” value. This forces the calculator to update the answer.

Using the Calculator

When you first open the calculator it will look like this:

You will enter values on the LEFT SIDE of the calculator, with the exception of the “mg of binder per teaspoon” box on the right.

Wet Food

Cans and pouches evaluate the same way so there’s really no difference in what you will see on screen when using either of these options.

  1. Change the package type (canned, pouch, kibble)
    1. If using kibble, skip to the Dry Food section
  2. Change the measurement type (ounces or grams)
  3. Enter the % moisture in the food.
    1. You can use the Guaranteed Analysis amount on the food label
    2. If you have the As Fed amount you can use that instead.
  4. Enter the amount of phosphorus in the food.
    1. If you don’t know the phosphorus amount you can use 2.0.
  5. Change the ounces per can amount if needed
  6. Change the portion fed if needed
    1. I usually set this to 1 (one) so I know the total amount of binder needed for the whole can of food
  7. Change the mg of binder per teaspoon if needed
    1. 1200 mg per teaspoon is the amount in Thriving Pets Aluminum Hydroxide
    2. Phos-Bind is 1000 mg per teaspoon
    3. Other brands will have their own strength, it should be on the label

Using a hypothetical food that has 2.0% phosphorus and 82% moisture I would need to add 3/4 teaspoon (900 mg) of Thriving Pets aluminum hydroxide to an entire 3 oz can of food. But, if you look at the “aluminum hydroxide needed” amount you can see that I don’t actually need 900 mg, I really only need 771 mg, so I can try to approximate 0.6 teaspoons instead of using 3/4 teaspoons if I need to keep the binder amount lower.

Dry Food

Dry food is quite a bit different from wet food when using the calculator. When you switch to Kibble as the food type the calculator will look like this:

  1. Change the measurement type (ounces or grams)
  2. Enter the % moisture in the food.
    1. You can use the Guaranteed Analysis amount on the food label
    2. If you have the As Fed amount you can use that instead.
  3. Enter the amount of phosphorus in the food.
    1. If you don’t know the phosphorus amount you can use 2.0.
  4. Enter the ounces per cup
    1. This will be on the food package somewhere
    2. This might be in grams instead of ounces, so you might have to set the measurement type to grams
  5. Change the portion fed if needed
    1. I usually set this to 1 (one) so I know the total amount of binder needed for a measured cup of food
  6. Change the mg of binder per teaspoon if needed
    1. 1200 mg per teaspoon is the amount in Thriving Pets Aluminum Hydroxide
    2. Phos-Bind is 1000 mg per teaspoon
    3. Other brands will have their own strength, it should be on the label
  7. Enter either the Calories per Cup or Calories per Kilogram
    1. The spacing here is weird and you’ll see 2 white boxes stacked on top of each other
    2. Calories per cup goes in the top box
    3. Calories per kilogram goes in the bottom box

Using a hypothetical food that has 2.0% phosphorus and 10% moisture I would need to add 3 teaspoons (3600 mg) of Thriving Pets aluminum hydroxide to one measured cup of food.

Compare Calculator to Other Ranges

Now that I have aluminum hydroxide amounts based on food I can compare them to the other dosing protocols to make sure they’re safe to give.

Here’s an example using my cat Thomas and my hypothetical foods that had 2% phosphorus:

Thomas’s Weight7.5 pounds
Current phosphorus level8.0
Maximum allowed binder amount from dosing protocols680 mg
Binder needed for 3 oz can of wet food900 mg
Binder needed for 1 cup of dry food3600 mg

In this example I can see that the amount of binder needed for these foods based on phosphorus content is higher than the total amount allowed per day by the most aggressive dosing protocol. In this case I would stick to the 680 mg maximum and divide it evenly among his meals. In fact, the amount of binder needed for just 1 can of food exceed the whole amount he’s allowed per day, and he eats more than 1 can a day.

Using a different food, one that is 0.9% phosphorus I get these results:

Thomas’s Weight7.5 pounds
Current phosphorus level8.0
Maximum allowed binder amount from dosing protocols680 mg
Binder needed for 3 oz can of wet food300 mg

Assuming Thomas eats only 2 cans of food per day I could safely dose his binder based on the phosphorus level in the food. In this case he’d be getting 600 mg total per day, which is safely below the maximum amount of 680 mg that he can receive.