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Optimizing formulas for the delivery of actives
Hello all
I recently completed a course on how to optimize formulations for the the delivery of actives. The focus was on actives that are backed by science i.e. Retinols, Alpha Hydroxy acids, Beta Hydroxy acids, Niacinamide, etc. Some literature was presented and the list below are some of the factors that where determined to have an impact on the efficacy of a formulation: how well the active is delivered to the right layer of the skin, and the expected benefit is achieved.
- Particle size of the emulsion (this seems obvious why)
- Type of formulation; Polymeric, O/W emulsions, solution, etc.
- Choice of emulsifier
- Approach to solubilizing the active
- Use of penetration enhancers
If you have experience formulating with actives or assessing efficacy, I would like to hear your opinion on this. Do these factors affect delivery of actives? If they do, what are some of the rules of thumb to follow in your experience? Are there any other things to consider?
I understand that ultimately everything depends on what is in the formula. I am just curious to know if anyone here has any experience to share.
Thank you!
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10 Replies
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watch Perry and Belinda
Latest Q&A session >>>>
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@Pattsi where can we watch it?
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@ccchem I would have added to the list you posted the following aspects:
- Molecular weight of an active
- Hydrophilicity/ Lipophilicity of an active substance
- Condition of the Stratum Corneum and its barrier system
- Understanding what an active is going to do when it reaches a particular layer in the SC/the mode of action/biochemical transformation or utilization
All these factors along with those that you have mentioned above will have an impact on penetration and the delivery.
I can not tell any rule of thumb, because the system of the delivery will highly depend on a particular substance that you want to include in your formula.
For instance, keratolytic formulations with Urea are going to be more efficient in the presence of acids and polyols. -
Pattsi said:watch Perry and Belinda
Latest Q&A session >>>>
Thanks for your suggestion. I actually attended this Q&A
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vitalys said:@ccchem I would have added to the list you posted the following aspects:
- Molecular weight of an active
- Hydrophilicity/ Lipophilicity of an active substance
- Condition of the Stratum Corneum and its barrier system
- Understanding what an active is going to do when it reaches a particular layer in the SC/the mode of action/biochemical transformation or utilization
All these factors along with those that you have mentioned above will have an impact on penetration and the delivery.
I can not tell any rule of thumb, because the system of the delivery will highly depend on a particular substance that you want to include in your formula.
For instance, keratolytic formulations with Urea are going to be more efficient in the presence of acids and polyols.@vitalys Thank you so much for this response! This is the kind of information I was looking for. I have noticed keratolytic formulations with Urea usually include Salicylic acid - thanks for this nugget.
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@ccchem You are very welcome
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@ccchem:
I would be interested in knowing what you learned about these two topics:- Type of formulation; Polymeric, O/W emulsions, solution, etc.
- Choice of emulsifier
Unless I am mistaken, the only way one knows for certain what is penetrating the skin is through tests on cadaver skin or some sort of equivalent model, but this is quite a “black box” of a topic. For example, I stumbled upon one recent journal article that was outside my comprehension but seemed to suggest that liposomes do not actually deliver ingredients through the epidermis, as many would have us believe.
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vitalys said:- Understanding what an active is going to do when it reaches a particular layer in the SC/the mode of action/biochemical transformation or utilization
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@ccchem - It’s not as simple as deeper is better.
There’s issue with ensuring consumer safety.
And then even if you can manage to go to Stratum Basale, how will you determine it not cross through to Dermis.Abdullah said:@Pattsi where can we watch it?It’s on the right side of the page. follow my arrows you will see it.
suswang8 said:“black box”????
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suswang8 said:@ccchem:
I would be interested in knowing what you learned about these two topics:- Type of formulation; Polymeric, O/W emulsions, solution, etc.
- Choice of emulsifier
Unless I am mistaken, the only way one knows for certain what is penetrating the skin is through tests on cadaver skin or some sort of equivalent model, but this is quite a “black box” of a topic. For example, I stumbled upon one recent journal article that was outside my comprehension but seemed to suggest that liposomes do not actually deliver ingredients through the epidermis, as many would have us believe.
@suswang8 You’re right - it certainly is a black box. That’s why I’m calling on people’s experience here.
In this example the researchers assessed the influence of the formulation type in the delivery of Glycolic acid and Glycerol. They compared an aqueous solution, a 30% propylene glycol (PG) aqueous solution, an oil-in-water (O/W) emulsion, a water-in-oil (W/O) emulsion, and two nonionic liposomal systems. You can read more about it here
For the choice of the emulsifier read more here and here (page 9)
Let me know what you think.
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