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Vial Sizes and Concentrations

We want to determine what vial sizes and concentrations are a good fit, maximizing both. As we’ve said in other places, the official recommendation from USP/FDA, etc. is that vials be discarded 28 days after puncture. But, we’re going to call 12 weeks a rough good cutoff point for vials considering that any official number will be highly conservative.

Assuming a 5mg dose and a 0.035mL dead space:

Concentration Dose Vol. + ~Dead Space Vial Size Doses
20mg/mL 0.25mL 0.285mL 2mL 7
20mg/mL     5mL 17
40mg/mL 0.125mL 0.16mL 2mL 12
40mg/mL     5mL 31

We could extrapolate this out further, but we think what it says is pretty apparent: 5mL is too large of a vial size for high-concentration brews and 40mg/mL in a 2mL vial is perfectly sized to last 12 weeks.

Until we are able to conduct some experiments to determine how long these vials can last without contamination, being punctured regularly or even after a single puncture and being left around, then we think it’s best to hug closer to official guidelines.

We believe 3 times the official guideline is still okay seeing as many folks are putting 40mg/mL into 10mL vials, and using it for over a year. They are hopefully using extra benzyl alcohol (but not a toxic amount), but without further research that’s not something we’re willing to do or advocate for.

Now, most homebrewers will brew at a 40mg/mL concentration, and often distribute a 10mL vial, effectively containing two years worth of HRT in a single vial. This is a bad idea. The FDA requires that all vials are discarded 28 days after first puncture. And like, sure, ACAB, and truly the FDA is probably way too conservative, but also… they’re probably not that wrong here. Another issue to consider is coring. If you puncture your vial every week for a year eventually you run the risk of causing some rubber to fall into your meds. We’ve seen vials core in under 8 weeks due to poor puncturing techniques.