Ointment is evenly spread on the skin, in contrast to creams and solutions

BACKGROUND: The efficacy of topical therapy depends on the patient spreading the topical drug in an even layer to give a standard dose. Ointments are believed to be more effective than creams and solutions. OBJECTIVES: To compare the application and spreading of four different pharmaceutical vehicles. METHODS: Twenty-nine healthy volunteers applied a fixed amount (0.1 g) of solution (S), ointment (O), cream (C) and low-viscosity cream (LVC) to the abdominal skin. Area of spread, skin surface lipids (dependent on formulation) and changes in skin surface temperature (cooling due to evaporation of formulation water/alcohol) were measured. RESULTS: Area of spread: O = C = LVC = S. Skin surface lipids: O > C > LVC > S. Difference in skin surface lipids between centre and periphery: O < C = LVC = S. Cooling: O < C = LVC < S. CONCLUSIONS: The four formulations were spread to similar areas. The ointment was spread evenly in the treated area while the other formulations were unevenly spread, with a lower dose in the periphery. Creams and solutions have disadvantages as vehicles, as rapid evaporation of formulation water/alcohol, measured as cooling, influences spread, resulting in an uneven topical dose within the treated area. In contrast, ointment is evenly spread and is thus a more appropriate formulation. Patients should be instructed to apply creams and solutions to multiple sites and to spread them quickly.