Bacteriostatic vs Sodium Chloride with Retatrutide- pics included

[GLP1Pharmacist]

Just wanted to show my recent experience with reconstitution with Hospira Bacteriostatic water and 0.9% NaCl Saline/sodium chloride.

These were both mixed the same lot and manufacturer of Retatrutide.

Sodium Chloride is often used to dilute medications but it appears to have participated out the Retatrutide. Mixed perfectly and no issues with Bacteriostatic water.

 

[ZippityDooDah]

Nothing beats a nice clear visual aid, thanks!

It fascinates me that this occurs since normal saline (NaCl water) is such a common component in medicine, whether administered subcutaneously, intramuscularly, or intravenously (not to mention inhalation, irrigation, etc.). Combine that with the fact that it's considered isotonic with our physiology, part of me wonders if reta makes a similar transformation once it's been injected.

 

[Morbius]

Very interesting, thanks for doing this.

It certainly looks like it precipitated, there's a gradient. I suppose it is possible that it still hasn't lost efficacy, though precipitation would make it harder to get a uniform draw.

 

[Calm Logic]

Google Gemini, boring me to saline tears:

Here's why Retatrutide might salt out in 0.9% NaCl saline while Tirzepatide might not:

* Differences in Amino Acid Composition and Net Charge:
* Hydrophobicity/Hydrophilicity: Peptides are made of amino acids, which can be hydrophobic (water-fearing) or hydrophilic (water-loving). The overall balance of these residues significantly impacts solubility.

* Retatrutide (C221H342N46O68): Looking at its reported sequence and modifications, Retatrutide contains several modified amino acids (e.g., 2-aminoisobutyric acid (AiB), alpha-methyl leucine (MeL), and a large C20 diacid modification on a lysine). These modifications can introduce significant hydrophobic character. While it also has charged residues, the overall balance might lean towards being more susceptible to "salting out" when exposed to higher ionic strength. Some sources indicate Retatrutide needs pH adjustment (to pH 7 or 9) for good water solubility, suggesting it's sensitive to ionic conditions.

* Tirzepatide (C225H348N48O68): Tirzepatide also has a C20 fatty diacid moiety conjugated to a lysine residue. However, the specific placement and nature of this modification, combined with the overall amino acid sequence, might result in a more favorable balance of hydrophilic and hydrophobic interactions, or perhaps a different distribution of charged groups that makes it less prone to precipitation in saline. Tirzepatide is often described as being soluble in water and sparingly soluble in PBS (which is a buffered saline solution), suggesting it handles saline better than Retatrutide.

* Specific Chemical Modifications:
* Both peptides have fatty acid modifications (C20 diacid). These modifications are generally to extend the half-life by enabling albumin binding. However, the linker used to attach this fatty acid and its point of attachment on the peptide chain can critically influence the overall molecule's conformation and interaction with solvents.
* Small differences in these linkers or attachment points could expose different parts of the peptide to the solvent, making one more prone to aggregation or precipitation in a high-salt environment than the other.

* Isoelectric Point (pI):
* Every protein or peptide has an isoelectric point (pI), which is the pH at which its net electrical charge is zero. Proteins are generally least soluble at their pI because there are fewer repulsive forces between molecules to keep them apart, leading to aggregation and precipitation.
* It's possible that the pI of Retatrutide is closer to the pH of 0.9% NaCl saline (~5.5-6.5) than the pI of Tirzepatide. If Retatrutide's pI falls within this range, or if the ionic strength of saline pushes its effective pI closer to the solution's pH, it would be more susceptible to precipitation.

* Formulation Differences (Excipients):
* While you mentioned mixing your own, it's crucial to remember that commercially available lyophilized drug products often contain excipients (e.g., stabilizers, bulking agents, buffers) that are critical for maintaining solubility and stability upon reconstitution.
* Even if you obtained "raw" Retatrutide and Tirzepatide, their original pharmaceutical formulations (if they were designed to be commercial products) would have carefully selected excipients. It's possible that the commercial Retatrutide product might require specific excipients (which aren't present if you're using a generic powder) that help it stay in solution in saline, whereas Tirzepatide's inherent properties or the excipients in its typical formulation make it more robust in saline.

* Aggregation Propensity:
* Some peptide sequences have inherent tendencies to aggregate, especially in unfavorable conditions (like high ionic strength). This might be due to specific "hot spots" in their amino acid sequence that promote self-association. Retatrutide's structure might simply have a higher intrinsic propensity for aggregation in the presence of competing ions from saline.

In summary: The difference in "salting out" behavior between Retatrutide and Tirzepatide in saline likely boils down to subtle but critical differences in their:

* Specific amino acid sequence and overall balance of hydrophilic/hydrophobic residues.
* Nature and placement of chemical modifications (like the fatty acid chains and linkers).
* Isoelectric points (pI) relative to the pH of the diluent.
* Inherent conformational stability and propensity for aggregation in different ionic environments.

These factors determine how strongly the peptide molecules interact with water molecules versus with each other (or the salt ions), ultimately dictating their solubility. Always refer to the manufacturer's specific reconstitution instructions for any medication to ensure proper preparation and patient safety.

 

[esdsafepoet]

Interesting results. There was a discussion in another thread that peptides like tirzepatide came from Eli Lily in a saline solution, but no one was sure on whether the same would be true for retatrutide.

Decided to try a little experiment here with tirzepatide, so I mixed up two vials, one with bacteriostatic saline, and the other with bacteriostatic water. Both came out crystal clear. But there was an oddity I discovered when trying to filter:

I have some overkill 0.02 micro filters, and the solution with bacteriostatic saline would not push through the filter at all, not a drop. I made a red mark on my hand trying to push the syringe and nothing would come out. I switched over to a 0.22 micron filter, and the saline tirz solution went through fine. I then tried the same with the bac water tirz solution, and I was able to push through the 0.02 micron filter no problem (thanks to zpped for the suggestion on the vent needle, btw).

So I'm thinking it must be one of two things: 1) the salt isn't dissolved well enough in the saline solution (seems odd, coming from Pfizer), and it clogs the filter, or 2) there's some micro-aggregation of the salt and peptide, enough to clog a 0.02 filter, but not so much that the solution looks cloudy like the reta solution.

I'm also aware this is probably useless information, but I killed a lot of $ in filters with this silly experiment, so figured I'd report something.

I wonder if when reta hits the mainstream market if we'll see it in a saline solution or something else. Very interesting that it might be incompatible with saline, whereas tirz is fine/sorta fine with saline.

Pic: this is just the reconstituted saline tirz solution in the original vial before filtering.

 

[DeafJam]

Interesting results. There was a discussion in another thread that peptides like tirzepatide came from Eli Lily in a saline solution, but no one was sure on whether the same would be true for retatrutide.

Decided to try a little experiment here with tirzepatide, so I mixed up two vials, one with bacteriostatic saline, and the other with bacteriostatic water. Both came out crystal clear. But there was an oddity I discovered when trying to filter:

I have some overkill 0.02 micro filters, and the solution with bacteriostatic saline would not push through the filter at all, not a drop. I made a red mark on my hand trying to push the syringe and nothing would come out. I switched over to a 0.22 micron filter, and the saline tirz solution went through fine. I then tried the same with the bac water tirz solution, and I was able to push through the 0.02 micron filter no problem (thanks to zpped for the suggestion on the vent needle, btw).

So I'm thinking it must be one of two things: 1) the salt isn't dissolved well enough in the saline solution (seems odd, coming from Pfizer), and it clogs the filter, or 2) there's some micro-aggregation of the salt and peptide, enough to clog a 0.02 filter, but not so much that the solution looks cloudy like the reta solution.

I'm also aware this is probably useless information, but I killed a lot of $ in filters with this silly experiment, so figured I'd report something.

I wonder if when reta hits the mainstream market if we'll see it in a saline solution or something else. Very interesting that it might be incompatible with saline, whereas tirz is fine/sorta fine with saline.

Pic: this is just the reconstituted saline tirz solution in the original vial before filtering.

View attachment 7358

Did you agitate the solution? Was it more viscous than usual?

I ask because I was traveling for work for a week and I was short a syringe and wound up making syrup with Reta. I pulled Reta into my peptide shot as my last draw. It was either BPC/TB or IPA/CJC no DAC all with BAC. The Reta gelled instantly, turned milky, and suspended in the peptide solution like a jellyfish shot in the syringe. At that point, I choose not to take the injection. I pushed in the syringe to inject the waste into the trash and it did not go back through as it was too viscous. I gave it a very hard push and it shot out. When I felt the mixture, it had the consistency of syrup.

Needless to say, I never mixed them again.

 

[esdsafepoet]

Did you agitate the solution? Was it more viscous than usual?

I ask because I was traveling for work for a week and I was short a syringe and wound up making syrup with Reta. I pulled Reta into my peptide shot as my last draw. It was either BPC/TB or IPA/CJC no DAC all with BAC. The Reta gelled instantly, turned milky, and suspended in the peptide solution like a jellyfish shot in the syringe. At that point, I choose not to take the injection. I pushed in the syringe to inject the waste into the trash and it did not go back through as it was too viscous. I gave it a very hard push and it shot out. When I felt the mixture, it had the consistency of syrup.

Needless to say, I never mixed them again.

I rolled each vial a few times after reconstitution, but really couldn't tell a difference between the bac saline and bac water vials. Only when I tried to filter on the 0.02. Just took them both out of the fridge to look again, and they look the same.

Not sure photos are much help, but bac saline tirz on left, bac water tirz on right. The saline vial is slightly less full because of the wasted filters.

 

[GLP1Pharmacist]

Did you agitate the solution? Was it more viscous than usual?

I ask because I was traveling for work for a week and I was short a syringe and wound up making syrup with Reta. I pulled Reta into my peptide shot as my last draw. It was either BPC/TB or IPA/CJC no DAC all with BAC. The Reta gelled instantly, turned milky, and suspended in the peptide solution like a jellyfish shot in the syringe. At that point, I choose not to take the injection. I pushed in the syringe to inject the waste into the trash and it did not go back through as it was too viscous. I gave it a very hard push and it shot out. When I felt the mixture, it had the consistency of syrup.

Needless to say, I never mixed them again.

Yes, agitated and no real change. Let sit for several days and same results. I may try adding 1.5ml of bacteriostatic water to see if it dissolves but decided not to take regardless.

 

[zpped]

Starting off with, I am not a chemist. But it's been pointed out by others in the community that are deeply involved in research chemistry that Reta is not compatible with saline. This has been shown through experimentation as well.

It's not an issue with tirz or sema.

 

[Calm Logic]

by others in the community that are deeply involved in research chemistry

Did they say why?

 

[zpped]

Did they say why?

Their specific answer was something along the lines of, looking at the chain of amino acids they could tell it wasn't going to work. My guess is it's not a simple explanation. (I asked, but they never responded) But it's been backed up through experimentation multiple times so I'm not bothered to try and understand any deeper.

 

[Calm Logic]

Their specific answer was something along the lines of, looking at the chain of amino acids they could tell it wasn't going to work.

That's impressive.

 

[keangkong]

Just wanted to show my recent experience with reconstitution with Hospira Bacteriostatic water and 0.9% NaCl Saline/sodium chloride.

These were both mixed the same lot and manufacturer of Retatrutide.

Sodium Chloride is often used to dilute medications but it appears to have participated out the Retatrutide. Mixed perfectly and no issues with Bacteriostatic water.

It's interesting that folks buy GLP-1 drugs from nonapproved vendors yet insist on using the approved stuff for their water. I'm not really knocking those who do because I've only used Hospira and Peptide Group Buys BAC water ever since I had a bad experience using some reconstitution solution off Amazon. Basically, after I looked at the stuff in the vial containing the BAC water and the peptide, I was no longer willing to inject it. I don't consider my bare eye a good judge of peptide quality and purity, however, I'm not injecting myself with cloudy stuff. Thanks for showing us the results of your experiment.

 

[zpped]

It's interesting that folks buy GLP-1 drugs from nonapproved vendors yet insist on using the approved stuff for their water. I'm not really knocking those who do because I've only used Hospira and Peptide Group Buys BAC water ever since I had a bad experience using some reconstitution solution off Amazon. Basically, after I looked at the stuff in the vial containing the BAC water and the peptide, I was no longer willing to inject it. I don't consider my bare eye a good judge of peptide quality and purity, however, I'm not injecting myself with cloudy stuff. Thanks for showing us the results of your experiment.

Because some things are much easier to make than others...
Relevant XKCD (although a bit out dated with more recent breakthroughs)