The dynamics of variable-in-shape drug particles are fundamental to predict the dissolution of drugs in a fluid. In this talk we propose a new approach which consists of describing the dissolution process of a drug particle using the level-set method. In this way, it is possible to recover the particle surface at any time as the zero level set of the solution of an Hamilton-Jacobi equation. This approach extends a previous work of 2022, and it allows us to deal with particles with rectangular shape as well as to simulate the joint dissolution of multiple particles with different shape and size. Firstly, we introduce the problem and the basic functions that come into play in the dissolution process, then we present the new methodology and finally we discuss some numerical simulations in the 2D case.