  The study of competition among brands in a common category is an interesting
strategic issue for involved firms. Sales monitoring and prediction of
competitors' performance represent relevant tools for management. In the
pharmaceutical market, the diffusion of product knowledge plays a special role,
different from the role it plays in other competing fields. This latent feature
naturally affects the evolution of drugs' performances in terms of the number
of packages sold. In this paper, we propose an innovation diffusion model that
takes the spread of knowledge into account. We are motivated by the need of
modeling competition of two antidiabetic drugs in the Italian market.
