FPGEE for National Association of Boards of Pharmacy (NABP) Practice Exam

Calamine lotion is classified as which type of emulsion?

1. Oil in water emulsion

2. Water in oil emulsion

3. Nanoparticle emulsion

4. Solid emulsion

The correct answer is: Water in oil emulsion

Calamine lotion is classified as a water-in-oil emulsion. This classification means that the water droplets are dispersed in a continuous oil phase. In the case of calamine lotion, the preparation includes a significant aqueous component, providing soothing effects for skin irritation, while the oil phase helps to maintain moisture and improve skin application. The water-in-oil emulsion is beneficial for specific applications like calamine lotion as it creates a barrier on the skin that is effective in protecting against irritants and providing a long-lasting soothing effect. This is particularly important when treating conditions like minor skin irritations, sunburn, or insect bites, where both the moisturizing and protective properties are desired. While an oil-in-water emulsion was a potential consideration, it is less characteristic of calamine lotion, which typically presents a thicker consistency due to its high oil content. Thus, the emulsion type directly relates to the product's physical properties and therapeutic benefits. The other choices like nanoparticle emulsion and solid emulsion do not accurately fit the formulation or delivery mechanism of calamine lotion, further reinforcing that a water-in-oil classification is most appropriate.