Actual number of doses per vial

[JustSomeGuy050]

I’ve had my RS on Reta for a few months now. One of the things I’ve noticed is that I seem to be getting a difference in the theoretical # of doses per vial (example: 10mg w/ 1.0mL Bac @ 2mg dose should give 5 doses @ 20 units) and the actual doses per vial (3-4 with that same math).
I’ve ran my math through so many reconstitution and dosing calculators to make sure I’m not screwing it up.
I do filter with a 4mm filter.
For the last recon I had 12mg and I filtered it with 1mL bac and purged with 0.5mL to give me 12mg/1.5mL for a 2mg dose @ 25 units.
But my RS is 3 shots in to the vial and it looks like there’s only 1 more dose left.
What could I be screwing up? Or is this normal?

 

[Sasquatch]

Why are you jumping back and forth from milliters to units for the dilution?

 

[CNCCurrency]

I’ve had my RS on Reta for a few months now. One of the things I’ve noticed is that I seem to be getting a difference in the theoretical # of doses per vial (example: 10mg w/ 1.0mL Bac @ 2mg dose should give 5 doses @ 20 units) and the actual doses per vial (3-4 with that same math).
I’ve ran my math through so many reconstitution and dosing calculators to make sure I’m not screwing it up.
I do filter with a 4mm filter.
For the last recon I had 12mg and I filtered it with 1mL bac and purged with 0.5mL to give me 12mg/1.5mL for a 2mg dose @ 25 units.
But my RS is 3 shots in to the vial and it looks like there’s only 1 more dose left.
What could I be screwing up? Or is this normal?

No need for RS on here.

 

[jsc1980]

What type of syringe are you using for recon and injecting? Luer loc syringes can have up to 0.1ml (10iu) dead space. So, you could be losing 20 units (one dose) from dead space. Try removing the needle, drawing in some air and air purging to clear some of that dead space.

 

[bada bing]

Every time you move a solution with a syringe and needle there will be small hold back losses. You'll lose a little more by dividing a vial up into many doses rather than one or two, every syringe pull incurs a loss. That said, it shouldn't be much, a unit or two over a vial with proper technique.

 

[jsc1980]

Every time you move a solution with a syringe and needle there will be small hold back losses. You'll lose a little more by dividing a vial up into many doses rather than one or two, every syringe pull incurs a loss. That said, it shouldn't be much, a unit or two over a vial with proper technique.

True if you use a fixed needle syringe, but luer lock syringes/needles have larger dead space. If you are adding bac to a vial, then removing the reconned pep and filtering into a new vial and are swapping needles multiple times without air purging, you could be losing close to 20 units. Even with an air purge, you'll lose a little but much less.

I use luer loc syringes when I inject my trt and leave an air bubble of 5-10 units in the syringe (let the bubble float to the plunger side before starting to inject) so I clear the majority of that dead space.

 

[CNCCurrency]

True if you use a fixed needle syringe, but luer lock syringes/needles have larger dead space. If you are adding bac to a vial, then removing the reconned pep and filtering into a new vial and are swapping needles multiple times without air purging, you could be losing close to 20 units. Even with an air purge, you'll lose a little but much less.

I use luer loc syringes when I inject my trt and leave an air bubble of 5-10 units in the syringe (let the bubble float to the plunger side before starting to inject) so I clear the majority of that dead space.

I use them and filter, I add a little extra bac to compensate or flush.

 

[BrightCandle]

The filter holds onto some liquid as does the syringe and its hard to grab every drop out of the vial and then every further syringe pull pin is also wasting a little. There is deadspace holding onto liquid in every single item, the filter especially holds onto quite a bit. 1mg with 0.2mg doses is really just 4 doses as you have to account for the losses which are pretty substantial once you take 1+4 syringe actions + filter into account.

You can reduce the amount of loss by reconing with more BAC as its a fixed cost per "syringe action" and filter so if you move to 2ml or 3ml the loss in liquid would be the same and you will end up with more units of the 5 pin. Its also why a lot of people use reusable pens with a cartridge, you only pull from the vial the once and pay a ~15 unit loss within the cartridge but you don't lose the 5-10 units per pin from the syrginge. I feel like the trade off is at about 4 pins a month, if you exceed that cartridge pens save a lot of liquid but below that its often not saving much.

I think you pretty much have to always math on the basis that you lose something like 20 units of liquid from a vial at least.

 

[CNCCurrency]

The filter holds onto some liquid as does the syringe and its hard to grab every drop out of the vial and then every further syringe pull pin is also wasting a little. There is deadspace holding onto liquid in every single item, the filter especially holds onto quite a bit. 1mg with 0.2mg doses is really just 4 doses as you have to account for the losses which are pretty substantial once you take 1+4 syringe actions + filter into account.

You can reduce the amount of loss by reconing with more BAC as its a fixed cost per "syringe action" and filter so if you move to 2ml or 3ml the loss in liquid would be the same and you will end up with more units of the 5 pin. Its also why a lot of people use reusable pens with a cartridge, you only pull from the vial the once and pay a ~15 unit loss within the cartridge but you don't lose the 5-10 units per pin from the syrginge. I feel like the trade off is at about 4 pins a month, if you exceed that cartridge pens save a lot of liquid but below that its often not saving much.

I think you pretty much have to always math on the basis that you lose something like 20 units of liquid from a vial at least.

I add a little extra bac to compensate or flush.

 

[eidos]

It's not a math problem, but a matter of good practice.

With every manipulation, there are measurement errors, syringes are not calibrated micropipettes, and there are losses.

If you want to lose less, dilute more. If you lower the concentration but keep the same volume, you lose less in terms of quantity. It's basic chemistry math: C = q/V

Check how much is actually left in the vial at the end of the process. With injection pens, this is easy as they usually have a graduated scale.