What is the inert filler in caffeine pills?

The inert filler in caffeine pills is typically microcrystalline cellulose, which is a white, odorless, tasteless powder that is derived from wood pulp. It is used as a filler in caffeine pills because it is an inexpensive, safe, and effective way to increase the bulk of the pill without adding any significant weight or volume. Microcrystalline cellulose is also commonly used as a filler in other types of pills, tablets, and capsules.