Question
Posted on: March 6 2013A 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.
- 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.
- 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).
- The third group are the molecules, which have to enter the bloodstream. Preferably lipophilic and small molecular mass. BV testosterone.