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Question

Posted on: January 20 2015

Do I need to replace the non-ionogenic Cetomacrogel cream with hydrophilic anionic cream in the following regulation? Or by another non-ionogenic cream genre Ung aquosum non ionicus NF5?

I have an intern FTA that should make following preparation: resorcinol 2g, lidocaine. HCl 1 G, hydrocortisone 1 G, nabenzate 1 G, propylene glycol 1 g and cetomacrogol cream ad 100 g. Because of the presence of resorcinol, which is incompatible with Cetomacrogol, we replaced Cetomacrogolcreme by Ung emuls non ionicus NF5 given we with Hydrof Anionic Creme would get an incompatibility with the cationic lidocaineH +. We also replaced Nabenzate for the same reason by Aqua Connservans in the Ung emuls non ionicus NF 5. But when we added the solution of resorcinol in a little water to the preparation, did the creme still break? What makes Resorcinol not compatible with non-ionogenic ointment NF 5? For resorcinol, the TMF recommends the anionic cream.

Answer

Both Cetomacrogol cream TMF and non-ionogenic ointment (better cream) contain an emulsifier with a polyethylene glycol chain. So both are incompatible with resorcinol. This means Dar we are designated on another cream base. Logically, we could use a cetrimlde cream. But this is not common. Then the hydrophilic anionic cream with which we see an incompatibility with lidocaïneH +. As a major exception, Lidocaine HCl is compatible with anionic emulsifiers and polymers. Had this   been the case now as with procaïneHCl then we can solve this incompatibility by neutralizing Procaine H + with a little base like Triethanolamine. Or nabenzate had to be replaced by Nipagine-Nipasol seems not necessary to me. It is difficult to estimate the pH of the aqueous solution on a theorertic basis.