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Question

Posted on: March 6 2013

Indomethacin Gel 1%

The preparation should take into account a number of factors, including pH (must be between 5.4 and 5.8) The viscosity (this will be too low because we neutralize to pH 5) Indomethacin must be processed in its non-ionized form as it otherwise does not penetrate the skin properly.

Answer

You have correctly formulated the problem statement

  1. no polymer exceeds carbomer on cosmetic surface

     

  2. you wish a clear gel and indomethacin is insoluble in water so we use the Carbopolgel alcoholic SATA NF VI but with 70 g isopropanol instead of 50 g

     

  3. indomethacin is slightly stronger acid as carbomer and thus consumes the base present in this composition and converts itself partially to indomethicinate; let us hope PH +/-5.4 à 5.8 (maybe check)

     

  4. but the Carbomeergel has now become thinliquid!

     

  5. so we would think "add alkali" but all the added alkali reacts in the first place with the residual indomethacin and this until all the indomethacin is converted into its salt!!!!

     

  6. and this should not be; Therefore, we need to increase the reduced viscosity with a non-ionogenic viscosities enhancement substance

     

  7. the environment of our gel is alcoholic and consequently it is appropriate polymer HPC (as already chosen by you!); BV 1.5 g Klucel Middle Visceus.