a tamper - resistance envelope formed of a thermoplastic resin comprises two opposing panels having respective bottom and side wall edges bonded together to form a pocket therebetween . the top of the pocket is open for inserting an item into the pocket . each panel has an edge portion adjacent the opening . a bead of pressure - sensitive adhesive is applied along each of the edge portions , and the adhesive bead is heat - seal bonded to the thermoplastic edge portion . the edge portions are brought together to bring the adhesive beads into contact to close the opening . by heat - seal bonding the adhesive beads directly to the thermoplastic edge portions , the pressure sensitive adhesive is resistant to being open by supercooling .