Method of preparing a pharmaceutical cream and minimizing imiquimod impurity formation (at least four months storage)

  • US 7,902,244 B2
  • Filed: 02/01/2010
  • Issued: 03/08/2011
  • Est. Priority Date: 12/17/2004
  • Status: Active Grant
First Claim
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1. A method of preparing a pharmaceutical cream formulated with an oleic acid component and 1-(2-methylpropyl)-1H imidazo[4,5-c]quinolin-4-amine (imiquimod) and minimizing formation of imiquimod-related impurities in the prepared pharmaceutical cream during storage of the prepared pharmaceutical cream prior to application of the prepared pharmaceutical cream to a dermal or mucosal surface, said method comprising:

  • (a) preparing a water phase preparation for formulating the prepared pharmaceutical cream, the water phase preparation comprising pharmaceutically acceptable excipients;

    (b) preparing an oil phase preparation for formulating the prepared pharmaceutical cream, the oil phase preparation comprising imiquimod and an oleic acid component, wherein the oleic acid component contains at least about 80% oleic acid by weight as a fatty acid and has a peroxide value of no more than about 5 milliequivalents of oxygen per kilogram and contains less than about 1% by weight polar impurities at or prior to formulation;

    (c) adding said water phase preparation to said oil phase preparation to form an emulsion;

    (d) homogenizing the emulsion to formulate the prepared pharmaceutical cream;

    (e) storing the prepared pharmaceutical cream prior to use of the pharmaceutical cream; and

    (f) minimizing the formation of imiquimod-related impurities in the pharmaceutical cream during said storing of the pharmaceutical cream, as compared to an amount of imiquimod-related impurities formed in an identical pharmaceutical imiquimod cream but formulated with a compendial grade oleic acid component when the pharmaceutical cream and the identical pharmaceutical imiquimod cream are each stored under identical storage conditions for up to about four months after formulation.

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