Abstract: The invention relates to an envelope consisting of a flexible heat-sealable sheet, which includes a front surface and a rear surface laterally closed by at least one longitudinal weld, and on the other ends by a transversal weld, defining an inner cavity containing the drug in question, the front and rear surfaces of the envelope having on least one of the ends of the inner cavity protrusions consisting of a flap, separated from the inner cavity by a weld line or area. Said flap provides a surface for incorporating Braille markings in impact printing or ink printing, without affecting the air-tightness of the inner cavity. In one embodiment, said flap includes a precut line in an area adjacent to the inner cavity for tearing and removing the portion of the flap that incorporates the name of the drug, while preserving the integrity of the inner cavity.