People should dispose of unused prescription drugs rather than hold on to them since the drugs can be misused or accidently ingested and cause harm, argues a commentary published in CMAJ (Canadian Medical Association Journal).

Many people keep unused drugs because they think they may be able to use them later or simply because of the effort required for safe disposal. It is particularly dangerous to keep pain killers such as opioids and other drugs because they may be used as recreational drugs by others such as teenagers. As well, people may self-medicate for a new illness with a medication prescribed for a different condition.

"Unused prescription drugs are sometimes brought to "pill parties" (also called "pharm" or "Skittles" parties), where adolescents experiment with pills they select from the pool of medications brought by partygoers. With opioids in particular, some products contain enough active ingredient in a single tablet to cause death in a naive patient, especially if mixed with other sedatives or alcohol," writes Dr. Peter Wu of the University Health Network and the University of Toronto with coauthor Dr. David Juurlink, Sunnybrook Health Sciences Centre and the University of Toronto.

"It is sensible to encourage responsible disposal of unneeded or expired medications, but guidance on how to dispose of medications is lacking," write the authors.

National Prescription Drug Drop-Off Day on May 10 in Canada is an opportunity to raise awareness of the issue and encourage people to drop off unused drugs at pharmacies; pharmacists will accept used medications throughout the year.