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Question

Posted on: March 6 2013

A general question about the use of substances in dermatics. The base or the salt of the following substances should be used: lidocaine/lidocaineHCl, miconazole/Miconazol nitrate, fusidic acid/Na-fusidate,

Gentamicin/gentamicin sulfate, diclofenac/Na-diclofenac?
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Answer

You know that it is not always easy to advance clear principles as science becomes a maze rather than a straightforward path. This also applies to the absorption by the skin. But anyway I try it.
  1. The first group of molecules that we can distinguish are those that are expected to have a superficial effect and therefore little absorption. This group belongs to Miconazole nitrate after fusidate and gentamicin sulfate and miconazole. We often use a salt form or not water soluble well. Of course, the stability of the raw materials must be taken into account. This is the case for after-fusidinate, which is not stable in aqueous medium. Consequently, we find in Fucidine cr è me fusidic acid. Apparently, the low solubility is not an unsurmountable obstacle to the therapeutic effect. After-fusidinate is then used in the ointment.

  2. The second group are the molecules, which serve to penetrate the deeper layers of the skin. Of these substances we use rather the non-ionic form. But this does not mean that the protonated form is not absorbed. What is clear is that they are absorbed much slower. Below I would rank: Lidoca ï ne, diclofenac. If diclofenac is used a salt preferably a salt with an organic (lipophilic) base (see Voltaren).

  3. The third group are the molecules, which have to enter the bloodstream. Preferably lipophilic and small molecular mass. BV testosterone.