Oxycodone pain pills  (John Moore/Getty Images)

Most of the roughly 200 million opioid prescriptions dispensed in the United States each year are not finished by the patient for whom they are intended. No one knows how many unused opioid pills lie forgotten in American medicine cabinets and sock drawers, but it’s surely in the billions. This enormous reservoir of excess pills may be raided by addicted individuals (e.g., houseguests, holiday party attendees) or become the gateway to experiments in drug use or dealing by curious teenage children. Efforts to remove this threat to public health from American homes have made only a small dent in the problem.

The Drug Enforcement Administration runs prescription take-back days twice a year which allow anyone to drop off at designated locations any amount and type of pills, no questions asked. The most recent such event netted an astonishing 456 tons of pills. However, this total includes everything from OxyContin to Flintstone chewable vitamins. Only an unknown fraction of what is gathered on take-back days reduces risks of addiction and overdose.

Another limitation to national prescription take back days is they are special events held six months apart. As with recycling of bottles and cans, turning in excess medications must become more routinized to have a population-wide impact. Congress passed useful legislation in 2010 authorizing organizations that dispense opioids (e.g., pharmacies, hospitals, clinics) to operate prescription drop off locations throughout the year.

It’s a good idea that hasn’t taken off. Last month, the Government Accountability Office reported only 2.5 percent of eligible organizations are participating. The key barrier is financial: Maintaining the safe-like prescription drop-off container, training staff to follow the relevant regulations, and destroying the returned medication costs money. The state with the highest proportion of participating organizations — North Dakota at 32 percent — funds drop off programs on an ongoing basis through its state Board of Pharmacy. In the private sector, CVS Health recently volunteered to build 750 disposal kiosks in its pharmacies. Most public and private sector organizations have not been willing to absorb the costs of operating prescription drop-off sites.

Given opioid manufacturers’ billions of dollars in revenue and the fact that at least some of them played a significant part is starting the opioid epidemic, they seem an obvious deep pocket to tap for supporting return of excess opioids. Recycling of bottles in the United States was kick-started by cash deposits until it became a voluntary, widespread habit. Mandating opioid manufacturers pay a few bucks per returned bottle of pills to the patient and to the drop off location operator may be what is needed to make returning leftover medication as automatic and prevalent as recycling cans and bottles.