Large Guide: Mix

Recipe

Identify your recipe. If you’re making estradiol I recommend 20mg/mL and for testosterone I recommend 200mg/mL. There’s some analysis on what concentrations are best here and here.

Use the recipe calculator to determine your exact recipe. Follow the exact steps on this page.

Mixing

Follow the “Important Info” section on the recipe calculator page for info about how to properly mix everything.

Do all of your mixing in front of your flow hood. While your ingredients are not all technically sterile, there is no reason to mix them in a way that might introduce more contamination. For the same reason, your container and stirrer should also be sterilized and depyrogenated.

Mixing can be automated through the use of a magnetic stirrer, though with a little patience this is not necessary.

Applying Heat, Carefully

Heat can be used to accelerate the mixing process. I recommend a hot water bath or a hot plate at around 35°C / 95°F.

There is no definitive data on how hot you can get the API, however anecdotal evidence suggests that heating it up to 121°C/250°F will not cause break down.

Oil may not begin to break down until nearing its smoke point, which will vary from oil to oil.

Benzyl alcohol has a flash point of 100°C, meaning that at that temperature enough of it is evaporating that the fumes can be ignited. Additionally BA can produce benzaldehyde when heated under certain conditions. For these reasons we avoid exposing BA to heat in any way. Read more here.

The Handbook of Pharmecutical Excipients (6th edition) says of benzyl benzoate that “exposure to excessive heat (above 40°C[/104°F]) should be avoided.” While I don’t have more info on why, the implication is that it loses stability at that temperature.

Cover

After mixing, or even during mixing if you’re using a magnetic stirrer, you should keep your preparation covered with either a lid, or a double layer of aluminum foil. Never open the lid except when under the laminar flow hood.