Fifteen police departments in Western Massachusetts are offering permanent drop-off boxes where residents can dispose of unwanted prescription drugs. Northwestern District Attorney David Sullivan and the state Department of Public Health plan to unveil the boxes this week. The drop boxes will be located at police stations in Amherst, Athol, Belchertown, Erving, Easthampton, Deerfield, Granby, Greenfield, Hadley, Montague, Northampton, Orange, South Hadley, Sunderland, and Ware. Prescription and nonprescription drugs, vitamins, and veterinary medications can be dropped in the boxes. Needles, liquid medications, IV equipment, and chemotherapy drugs will not be accepted.