A process forms an implantable product including poly(glycerol sebacate) urethane (PGSU) loaded with an active pharmaceutical ingredient (API). The process includes homogeneously mixing a flowable poly(glycerol sebacate) (PGS) resin with the API and a catalyst to form a resin blend. The process also includes homogeneously combining the resin blend with an isocyanate to form a reaction mixture and injecting the reaction mixture to form the PGSU loaded with the API. An implantable product includes a PGSU loaded with an API. In some embodiments, the implantable product includes at least 40% w/w of the API, and the implantable product releases the API by surface degradation of the PGSU at a predetermined release rate for at least three months under physiological conditions. In some embodiments, the PGSU is formed from a PGS reacted with an isocyanate at an isocyanate-to-hydroxyl stoichiometric (crosslinking) ratio in the range of 1:0.25 to 1:1.25.