Conclusions
An improved potency classification system with the necessary clinical relevance to facilitate the choice of an appropriate potency for a specific indication is proposed. The TCP containing CP (Dermovate®) was found to be more potent than that containing MF (Elocon®) where the rank order was in line with existing classification systems. However, the inherent potency assessments of the TCs, CP and MF, showed opposite results. The potencies of the TCPs under investigation were then compared to the inherent potencies of their corresponding TCs. It was observed that the potency of the TCP containing 0.05% CP (Dermovate®) was higher than its corresponding TC, even though the concentration of the drug in the TCP was 50% lower than the TC solution (0.1%). Furthermore, Elocon®, despite containing the same strength of MF (0.1%) exhibited a reduced potency compared to the TC API itself. Although the inherent potency of MF was shown to be higher than that of CP, when the TCs are formulated into products, the potencies were altered. Hence, potency of a TC may be increased or decreased based on the type of formulation and vehicle components. These data clearly indicate the effects and importance of formulation on TCs. Furthermore, inconsistencies seen in the existing TCP classification systems, stresses the need for the development of an improved potency classification system that consistently ranks the potencies of TCPs by using standardised and validated methods.