minimum benzyl alcohol concentration needed to be bacteriostatic?

[faenor1916]

Hello,

Newbie question here, but I can't easily find an answer on the internet. I'm looking to transfer prefilled syringes that are sterile water and TZ 5m/0.5ml into vials so that RS can take 2.5mg doses twice a week (instead of 5mg dose once a week). I'm trying to figure out what the minimum percentage of benzyl alcohol is required to make a solution bacteriostatic. I'd like to add 1ml BAC water to 1ml TZ solution (two prefilled syringes), which would put the benzyl alcohol percentage around 4.5%, but I don't know if that's enough to make the solution bacteriostatic. If the concentration needs to stay at 0.9-1.1% to remain bacteriostatic, then obviously I can't make this work as it will always dilute below that if I add the TZ solution, but maybe there's a lower percentage that would still work?

Thought someone here might know. Thanks for the help!

 

[Jailbreak7]

Hello,

Newbie question here, but I can't easily find an answer on the internet. I'm looking to transfer prefilled syringes that are sterile water and TZ 5m/0.5ml into vials so that RS can take 2.5mg doses twice a week (instead of 5mg dose once a week). I'm trying to figure out what the minimum percentage of benzyl alcohol is required to make a solution bacteriostatic. I'd like to add 1ml BAC water to 1ml TZ solution (two prefilled syringes), which would put the benzyl alcohol percentage around 4.5%, but I don't know if that's enough to make the solution bacteriostatic. If the concentration needs to stay at 0.9-1.1% to remain bacteriostatic, then obviously I can't make this work as it will always dilute below that if I add the TZ solution, but maybe there's a lower percentage that would still work?

Thought someone here might know. Thanks for the help!

hate to say it but you got all confused with this . get some BAC water that already has 0.9% benzyl alcohol in it and you're done.. you're overhinking this

 

[faenor1916]

Thanks RedSkip and Jailbreak7!

I think I'm either still confused or I didn't communicate clearly enough what I'm trying to do. Basically I want to put 1ml solution from 2 prefilled syringes [each have 0.5ml of sterile water (NOT BAC water) + 0.5mg Tirz] and 1ml of BAC water into a sterile vile, equaling 2ml of new solution. But only 1ml of that new 2ml solution is BAC water, which should mean that the benzyl alcohol concentration is now half of what it was as just BAC water, right? Because the other 1ml of the solution came from sterile water and 1mg Tirz, which has no benzyl alcohol in it, so it diluted the alcohol concentration.

Context: I'm doing this so that I can get two shots out of the one previously prefilled syringe and I'm not comfortable with simply reusing the prefilled syringe with a new sterile needle since it did NOT have BAC water in it originally. It will also have thawed out of previously frozen state and I'm not going to refreeze it, but will need to keep it in the fridge. I would then draw 4 shots (2.5mg Tirz in each at 0.5ml)

Assuming the above is correct, this new solution would have around 4.5% benzyl alcohol and I'm trying to figure out if that's enough alcohol to make a solution bacteriostatic.

thanks!

 

[RedSkip]

I think you will have a difficult time measuring the small amount of Benzyl Alcohol required to make 0.9% BAC solution since your volumes are so small. Even (1) drop of Benzyl will yield 0.05 mL, which is roughly 5x the required volume for a 1 mL solution.

EDIT: I re-read your post and then edited my post....

 

[RedSkip]

Thanks RedSkip and Jailbreak7!

I think I'm either still confused or I didn't communicate clearly enough what I'm trying to do. Basically I want to put 1ml solution from 2 prefilled syringes [each have 0.5ml of sterile water (NOT BAC water) + 0.5mg Tirz] and 1ml of BAC water into a sterile vile, equaling 2ml of new solution. But only 1ml of that new 2ml solution is BAC water, which should mean that the benzyl alcohol concentration is now half of what it was as just BAC water, right? Because the other 1ml of the solution came from sterile water and 1mg Tirz, which has no benzyl alcohol in it, so it diluted the alcohol concentration.

Context: I'm doing this so that I can get two shots out of the one previously prefilled syringe and I'm not comfortable with simply reusing the prefilled syringe with a new sterile needle since it did NOT have BAC water in it originally. It will also have thawed out of previously frozen state and I'm not going to refreeze it, but will need to keep it in the fridge. I would then draw 4 shots (2.5mg Tirz in each at 0.5ml)

Assuming the above is correct, this new solution would have around 4.5% benzyl alcohol and I'm trying to figure out if that's enough alcohol to make a solution bacteriostatic.

thanks!

I come up with the same math as you, but it's not 4.5% it 0.45%, since you added (1) mL of sterile fluid to the (1) mL of BAC. You doubled the volume which in turn halves the concentration of the BAC solution.

This is better than sterile water only, but I can't say if it's enough Benzyl to protect against microbial growth.

 

[faenor1916]

Thanks RedSkip, that's right! That's what I meant to say, 0.45%. And so the question is whether or not that's enough to actually make a solution bacteriostatic.

Oh, and as for your other post (also a good point), I'm actually only utilizing Hospira BAC water with it's preset alcohol percentage, so I'm not mixing in benzyl on its own.

 

[RedSkip]

At some point you reach a point of diminishing return...

 

[faenor1916]

At some point you reach a point of diminishing return...

View attachment 2812View attachment 2813

yep, that's right. I mean, I could add up to 3ml of BAC water to the vial, which would give me a 2.5mg Tirz/1 ml and I think an alcohol concentration of 0.675%. But that's about as high as I could make the alcohol concentration in terms of comfortability for a 2.5mg Tirz shot (I wouldn't want to inject more than 1ml of solution per a shot).

 

[RedSkip]

yep, that's right. I mean, I could add up to 3ml of BAC water to the vial, which would give me a 2.5mg Tirz/1 ml and I think an alcohol concentration of 0.675%. But that's about as high as I could make the alcohol concentration in terms of comfortability for a 2.5mg Tirz shot (I wouldn't want to inject more than 1ml of solution per a shot).

Understand your POV completely.

Another way to do it would be to buy 1 L of sterile water and inject the bag with Benzyl to give you a custom solution that you could utilize to get the required quantities. But, it would be wasteful and you'd have a solution that you likely won't use again.

 

[Glp1judd]

Can prefilled syringes be frozen? I thought only lypholized powder could be frozen and not degrade the peptide.

 

[RedSkip]

Can prefilled syringes be frozen? I thought only lypholized powder could be frozen and not degrade the peptide.

No. I believe he was referencing the lyophilized product being frozen not the syringes.

 

[ImSW1]

Can prefilled syringes be frozen? I thought only lypholized powder could be frozen and not degrade the peptide.

Of course they can be frozen. Little tough to inject, but I believe in you . Sorry, couldn't help myself.

 

[Glp1judd]

No. I believe he was referencing the lyophilized product being frozen not the syringes.

Maybe. Here’s the quote:

“Context: I'm doing this so that I can get two shots out of the one previously prefilled syringe and I'm not comfortable with simply reusing the prefilled syringe with a new sterile needle since it did NOT have BAC water in it originally. It will also have thawed out of previously frozen state and I'm not going to refreeze it, but will need to keep it in the fridge. I would then draw 4 shots (2.5mg Tirz in each at 0.5ml)”

 

[faenor1916]

yeah, the prefilled syringes are frozen. Not best practice, I know. But if you read enough opinions on it, it's still debated. Some claim the confusion has arisen because EL specifically says not to freeze their auto-injector pens, but because of mechanical issues, not because of the drug. Others say freezing solution in syringe will damage the Tirz.

I'm not here to support either way, I simply received them frozen from my pharmacy and was instructed to keep them frozen until use. They have CLEARLY been working (down 25 pounds), so at least some of the drug efficacy remains! This is the last of my compounding supply, and then I'll move to my new reconstituting supply which I will NOT be freezing in syringes. But I still need to finish this batch.

But back to original question at hand, which (understandably) no one has a strong answer for so far: is 4.5% benzyl alcohol strong enough to make a solution bacteriostatic?