A Prescription Drug Take Back Day is being held this weekend.  Danbury Police will be accepting unused, unwanted and expired medications from 10am to 2pm Saturday at police headquarters on Main Street.  Police warn that these medicines left in the house are a leading cause of accidental poisoning and contribute to drug abuse.  Medications flushed or thrown away can pollute waterways. During the national take back day, police will not be collecting needles and syringes, chemotherapeutic drugs, or radiopharmaceuticals and tracers.