Abstract: Barrier sheets for securement to the cover sheet of a multi-compartment medicinal dispensing device having a multi-chambered base to make the device impervious to moisture. The cover sheet includes plural closures releasably secured to one another along weakened lines. The barrier sheet is formed of a moisture impervious plastic and has a central portion and edge portions each including an adhesive on its underside surface. The central portion includes plural weakened lines corresponding to the weakened lines in the closures of the device. In one embodiment, each of the edge portions are narrow elongated flaps. The barrier sheet is secured to the cover sheet by disposing it on the cover sheet with the flaps folded around the edges of the cover sheet and into securement with the device base to seal the edges of the cover sheet.