The term "me-too drug" or "follow-on drug" refers to a medication that is similar to a pre-existing drug, usually by making minor modifications to the prototype, reflected in slight changes in the profiles of side effects or activity, and used to treat conditions for which drugs already exist. While pharmaceutical companies have justified the development of me-toos as offering incremental improvements in efficacy, side-effects, compliance and cost, critics have questioned the increasing marketing of me-toos, their absorption of research and development resources and their impact on the innovation of new treatments.