Coloration of phenothiazines with metal-containing drugs.

We studied the color change of phenothiazines and metal-containing drugs after compound formation, followed by use of FT-Raman spectrocopy to observe any structural changes in them. When 6 phenothiazines (thioridazine hydrochloride, prochlorperazine maleate, levomepromazine maleate, chlorpromazine phenolphthalinate, fluphenazine maleate and perphenazine fendiate) formed compounds with natural aluminum silicate, the color change was accompanied by a shift of FT-Raman signals. These changes could be attributed to the structural changes of phenothiazines. This present observation can be then used in advance to avoid coloration of phenothiazines during preparative procedures with metal-containing drugs such as antacids.