Electrophoretic evaluation of the mobility of drugs suitable for iontophoresis.

Iontophoresis is the process of increasing the penetration of drugs for therapeutic purposes using DC electricity. The most important factor for iontophoresis is the formation of drug ions in solution. On this basis, the penetration of any drug applied by iontophoresis might be maximized at an optimal pH. Seven medications were investigated: acyclovir, methylprednisolone sodium succinate, metronidazole, dexamethasone sodium phosphate, minoxidil, lidocaine hydrochloride, and adenine arabinoside monophosphate. Using techniques of paper electrophoresis, we evaluated the influence of pH on the mobility (mu) of the drugs in phosphate buffers at pH 5, 7, and 9. The mu-values were calculated after detecting the drugs on paper with ultraviolet light. The results indicate that the seven drugs had higher mu-values usually at one, but sometimes at two, of the pH values studied. This study suggests that a variation in pH might alter the maximum ionization, and therefore, the optimal mobility for these seven drugs, as well as other drugs, suited to iontophoresis.