Which statement correctly differentiates fusion from incorporation in ointment preparation?

• A. Fusion involves melting ingredients together, then cooling with stirring; incorporation involves mixing until uniformity.
• B. Fusion requires no heating; incorporation requires heating.
• C. Fusion uses water as solvent; incorporation uses oil.
• D. Fusion uses levigating agents; incorporation does not.

Answer: (A)

The essential point is how the two methods handle heat and mixing. In fusion, you heat the ingredients until they melt into one homogeneous melt, then you cool with constant stirring to form a uniform ointment. In incorporation, you don’t melt the base; you distribute the added material by mechanical mixing until uniform, sometimes using levigation to wet powders before mixing. This difference explains why fusion relies on melting and cooling to achieve uniformity, while incorporation achieves uniformity through thorough mixing (and possibly wetting of powders) without melting.

The other statements fail because fusion does involve heating, aqueous solvent isn’t a defining feature of fusion, and levigating agents are not used in the fusion method.