Medicine volume in water?

[tahiles]

Why do all the calculators assume the medicine won’t displace any water? It has to go somewhere.

But if you put in round figures for the medicine and water every calculator simply divides evenly. The medicine has to displace water resulting in a weaker dosage than the calculators indicate.

Am I crazy or is this amount too small to care about?

 

[bbrewer]

Why do all the calculators assume the medicine won’t displace any water? It has to go somewhere.

But if you put in round figures for the medicine and water every calculator simply divides evenly. The medicine has to displace water resulting in a weaker dosage than the calculators indicate.

Am I crazy or is this amount too small to care about?

You are not crazy, it is far too small to care about. It gets more complicated with solutions than adding volumes, the solution may just end up with a greater density than water.

 

[PurpleCatFur]

The volume change is minimal, most of the contents of a peptide vial are fillers like mannitol which is soluble. The density does change once the fillers and peptides are mixed and then dispensed any volume is change is not noticable without high precision measurement tools. The most I see in some peptides is a viscosity change.

 

[scarywood75]

Why do all the calculators assume the medicine won’t displace any water? It has to go somewhere.

But if you put in round figures for the medicine and water every calculator simply divides evenly. The medicine has to displace water resulting in a weaker dosage than the calculators indicate.

Am I crazy or is this amount too small to care about?

It's insignificant and you can't expect any precision anyway because :
- fill variation, even from the same batch
- residues left in vials/syringes/needles

And a precise dose wouldn't matter anyway

 

[Morbius]

Good question! But I agree it is impossible to do this perfectly and the solubility factor is not worth compensating for.

I was curious to calculate this to see the numbers anyway ... but actually had a hard time finding the info!

But even if we could calculate the exact volume change for mannitol... We don't know how much is in there, nor what else might be in there. So it's not fully solvable without a lot of info we can't get, and which may change batch to batch anyway.

Without this information I will continue to ...