A Nationwide Survey of Community Pharmacist Contributions to Polypharmacy in Opioid-Using and Non-using Cancer Patients in Japan.

No nationwide study on polypharmacy in palliative care among Japanese community pharmacies has yet been conducted. We conducted an online questionnaire survey for community pharmacist members of The Japanese Society for Pharmaceutical Palliative Care and Sciences regarding their contributions to cancer patients who regularly used six or more drugs, including opioids, in service during the two-month period from October to November 2017. Of 579 community pharmacists, 83 responded to the survey (14.3%). Among them, 47.0 and 27.7% of respondents replied that more than 40% of opioid-using and non-using cancer patients were prescribed six or more regular medications, respectively. The proportion of patients with polypharmacy was marginally higher among opioid-using than non-using patients. Additionally, 31.3 and 22.9% of respondents replied that a low or moderate rate of opioid-using and non-using patients with polypharmacy received inappropriate prescriptions, respectively, including "unnecessary medications," "adverse drug reactions" and "duplication of pharmacological effect." The proportion of patients who received inappropriate prescriptions was significantly higher among opioid-using than non-using patients. Furthermore, 37.3 and 19.3% of respondents replied that pharmacist's recommendations contributed to drug reduction in opioid-using and non-using patients with polypharmacy who received inappropriate prescriptions, respectively. The responders with higher confidence in palliative care showed more success rate for reducing inappropriate medications. Our findings suggest that opioid use can be associated with an increased risk of polypharmacy in cancer patients, and that recommendations by a population of community pharmacists can reduce inappropriate medications and improve adverse drug reactions in both opioid-using and non-using cancer patients with polypharmacy.