Sulfa AVS = Trimethoprim+Sulfadiazine not dissolving. Why?

[Stephanie]

The preparation of Trimethoprim + Sulfadiazine called 'Sulfa AVS' supplied to me by an avian vet does not dissolve fully. About 30% of it remains as a bright white powder that settles at the bottom of the container. Does anyone know what this is and whether it matters?

Thanks.

[MiaCarter]

Stephanie - That's not good.
It should dissolve. If it fails to dissolve, that means the liquid that it's suspended in has reached its saturation point. (You can only dissolve so much of a substance in liquid; the liquid can only hold so much. There will be a point where the substance no longer dissolves.)

So I would stir it up and try to promote dissolving. But if that doesn't work, I would shake it up real well before each dosage.
Some medications just separate naturally. My dog's insulin is like this. The white insulin settles to the bottom of the vial, and the suspension floats on the top.

[MiaCarter]

Update: I just mixed up some trimethoprim sulfa myself last night and it took a fair bit of shaking and stirring for it to dissolve fully. It seems it's rather stubborn, but it does eventually dissolve.
It's similar to Amoxitex. Amoxitex can be really stubborn, with little chunks/floaties that fail to dissolve. I've taken to warming the water a bit before I mix it in and it helps it to dissolve better.

[Stephanie]

Thanks Mia .

I did a great deal of shaking to no avail, but warming it up did help. Thing is, once outside in the cool air it fell out of solution again very quickly. So I can't be sure how much of each medication they ended up drinking.

It's strange that it's formulated this way - as a not very dissolvable product, but for administration in water. Puzzling.

[MiaCarter]

Well that's strange, isn't it?
It sounds like the water has reached its saturation point, since it keeps settling. Are you using a super high concentration?

Mine stayed dissolved in the water. It was one-quarter teaspoon per quart, so not a whole lot.

I'd just be sure to shake it up real well before you give it to them. That should allow you to give it while the medicine is equally distributed in the liquid.

[lou]

switch it around as how you mixed it the first time
lou