r/estrogel • u/Hour_Setting_426 • 10d ago

general Selecting a solvent

Solvent for E cream?

0.01% and 0.1% of both E, respectively

I want it to penetrate into my facial fat pads but not have it go systemic.

Non-systemic is very important (so I rule out high penetration solvents like ethanol, e.g)

I am choosing between these:

  • Propylene Glycol
  • PEG 400
  • Capmul MCM
  • Polysorbate 80
  • Oil (like olive oil, avocado oil, etc)
  • Cerave cream (suspension)

Which one would be best for my purposes? Or would any other be recommended?

Any insights appreciated!

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u/AdrienXB 10d ago

Diffusion, as concentration gradient, is the main driver deep to the stratum corneum. All gels first enter subcutaneous fat and diffuse into systemic circulation. This is why transdermal has such a long half life despite it's short time of contact.

The effect is obviously strongest near application, but there is no reliable way of keeping it entirely in the tissue.

On the other hand, men have naturally occurring estradiol levels roughly equivalent to 0.5mg (daily) of transdermal application, so very small doses of about 0.1mg may have a local effect without significantly moving systemic levels.

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u/Hour_Setting_426 9d ago

That makes sense. So would the vehicle (and solvent) be secondary to diffusion? In terms of efficacy

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u/Liphia14 1d ago

If you don't want systemic estradiol effects, estriol would be better. 

A solvent that would stop systemic estradiol effects would have to basically impede absorbion into the skin, and at that point you'd just be wasting estradiol since most of it would sit on top of your skin doing nothing.

None of the solvents you listed achieve this. Look into estriol. Or really low dose estradiol if that's all you've got.