Emulsion stabilizers that don't worsen skin feel or absorption

ZinkZink Member
edited September 2014 in Formulating
I'm interested in having a contract manufacturer make an acne treatment that's an oil in water emulsion medicated with benzoyl peroxide. But it appears that benzoyl peroxide can destabilize emulsions. The formula is basically 30% oil: sunflower seed oil, jojoba oil and shea butter emulsified using Cetearyl Alcohol and Polysorbate 60. The benzoyl peroxide is pre milled and mixed into a water based gel.

I've tested 0.4% Sodium Carbomer from lotioncrafter and it helps, but the emulsion destabilizes after a month at 45C. Xantham Gum (Clear), from lotioncrafter, extends stability to 3 months used at 0.4%, but makes absorption into the skin take twice as long.
Using Lotionpro165 (Glyceryl Stearate (and) PEG 100 Stearate) combined with Cetyl alcohol instead of Cetearyl and Polysorbate 60 stabilizes the lotion, but absorption is markedly hindered.

Any other thickeners or emulsifiers that could work with this type of formula?

HPMC, HEC, 
Magnesium Aluminum Silicate
Sodium Magnesium Silicate
Hydrogenated Vegetable Oil (Lipidthix)
Sclerotium Gum
Other grades of carbomer?

Comments

  • chemicalmattchemicalmatt Member, Professional Chemist
    ZInk, none of the above, with possible exception of magnesium aluminum silicate, are peroxide stable, and neither is sunflower oil.  Unsaturated carbon bonds do not like peroxygens (or, correction, yes they do, and a lot).  Ethoxylated linear alkyl alcohols work best, e.g. Steareth-2, Ceteareth-21, etc.
  • Thanks Matt, very interesting. I guess I'm shooting for peroxide stable enough, aiming for a 2 year shelf life or 2 months of retained stability at 45C.

    Do you know whether monounsaturation vs polyunsaturation makes a significant stability difference? And how much more stable are saturated oils? Would be interesting to look into this.

    Perhaps combining Steareth-2 with Ceteareth-21 could work as an emulsifier system? Any co emulsifiers that could help stability? How about polysorbates?
  • pmapma Member
    Just curious: why so much oil in an anti-acne product?
  • Chemist77Chemist77 Member, PCF student
    @pma
    maybe it's more like a vehicular component, selection is based on un-saturation I suppose to have something like non-comedogenic especially for an anti-acne product.
    Just a passing thought, though.
  • Yes, oils turn out to be good vehicles for benzoyl peroxide, and people with acne have seen good results moisturizing with non comedogenic oils.


  • So I have some ideas for changing the emulsifier system and then testing other thickeners, aiming for HLB 8. A combination of these low/high HLB emulsifiers:

    Low HLB
    Glyceryl Stearate 
    Steareth-2

    High HLB
    Ceteareth-20
    Cetearyl Alcohol
    Polysorbate 20

    Preblend
    Sepiplus 400
    Ewax NF (Control)

    Thickeners
    Carnabua Wax, Cetyl Alchohol, Sclerotium Gum, Magnesium Aluminum Silicate, Lipidthix, Permulen TR2.

    Any other ideas?





  • magnesium aluminum silicate is good for Benzoyl peroxide formulas! any updates on your project?
  • ZinkZink Member
    Yep, Sepiplus won out! Glyceryl Stearate was good in terms of stabilizing the lotion, but rub in was poor in all cases.

    Sclerotium Gum and Permulen TR2 were both good thickeners, Cetyl helped a bit when added. MAS did not help stability quite enough.
  • @zink thanks for the update!

    possibly a dumb question... would you put EOs into a benzoyl peroxide cream/gel?? will it get degraded but the BPO or vice versa??


  • ZinkZink Member
    EO?
  • BelassiBelassi Member
    edited March 2015
    Essential Oils. Which contain a huge variety of things, such as terpenes for instance. I wouldn't use essential oils in an anti-acne product except for specific ones known to have an anti-acne benefit, such as tea tree oil or thyme oil. But with benzoyl peroxide? I don't think so. 
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