20% Benzocaine Cream

I am trying to get 20% Benzocaine into a cream. I am dissolving it first into propylene glycol and then adding to the main batch but it always turns out gritty. Is there a better method to get it to stay in solution?


  • PharmaPharma Member, Pharmacist
    Either you use an oil-base for benzocaine, benzocaine hydrochloride for a water-based product, or use either of which in the opposite way to obtain a paste/suspension in which case you may be able to reduce grittiness by passing it through a three roll mill. Which product you choose depends on the intended use.
  • Thank you I will try these recommendations out!
  • PharmaPharma Member, Pharmacist
    Speed of action and depth/quantity of skin penetration depends on where you apply your product and which kind of product (gel, o/w, w/o, ointment) you use. Your first consideration shouldn't be to try things out but to determine which galenic form fist your demands best.
  • @Pharma ; this product will be used for feminine care.  I recently started working for a new company and it is a product they have been making, however they are having trouble scaling it up with that much benzocaine so I have been tasked with resolving this issue.  I am new to formulating OTC products and I am the only chemist here so I am trying to teach myself about these types of products.  Most of my experience is in hair care formulation so if you could recommend any resources that would be beneficial for formulating pharmaceutical applications that would be very much appreciated!
  • PharmaPharma Member, Pharmacist
    mhart123 said:
    ...feminine care...
    ...they are having trouble scaling it up...
    ...if you could recommend any resources that would be beneficial for formulating pharmaceutical applications...
    Feminine care? Benzocaine is not something to be used in a 'care' product, it's a pharmaceutical drug. For what exactly do you use 20%? Laser? Epilation? Tattoos?
    What kind of trouble? Why isn't it working or what's failing?
    A resource that would be beneficial: studying pharmacy? If you're fluent in German, the Neues Rezeptur-Formulatorium is a great resource. I don't know any English sites/books except USP and BP.
  • Like I said, I am new to this company and I do not have any experience formulating drug products.. only cosmetics.  It was a request from a customer to put it in at 20%, for itch relief, and they have been making the product for years now.  I believe it is their processing that is causing issues when they scale it up.  They premix it in propylene glycol and then add it to the emulsion around room temperature, however it turns out super gritty.  

    The melt point for benzocaine is around 90C so that is probably problem #1.  Second, I'm not sure if propylene glycol is the best choice to solubilize it. I am going to try out Peg-8 and Peg-75 as another option as well as maybe moving away from a cream base and making an oil-based product like you suggested.
  • PharmaPharma Member, Pharmacist
    I'm not suggesting anything for your purpose, I'm simply stating that there are other possible options. The difference is that some of these options will not perform the same as the original formula.
    It's weird that benzocaine is in solution first (PG isn't a bad solvent for it but it's susceptible to dilution with water) but then form crystals once emulsified only in the larger batch. How much did they upscale?
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