Background Opioid administration for pain control and relevant reports of adverse reactions have rapidly increased in the last several decades. In particular, elderly patients with various underlying disorders are administered with multiple drugs and prone to drug-drug interactions, and special attention is necessary in prescribing opioids.

Purpose This study attempted to verify the incidence rates of opioid adverse reactions, the symptomatic manifestations and examine causative factors in elderly male patients.

Material and methods This retrospective study, conducted via electronic medical records, included a total of 320 male patients, 65 years’ old or older, who had been prescribed with oral opioids in this hospital from 1 January to 31 December 2012. These participants were divided into two groups: group one for patients with adverse reaction manifestations (ARM) and another group for patients with no ARM. The correlations with age, body mass index, alcohol drinking and smoking, underlying diseases, previous opioid usage and concurrently-administered drugs were analysed.

Results Eighty-nine out of 320 patients (27.8%) developed adverse reactions. Among these adverse reactions, constipation was manifested in 36 patients (11.3%); gastrointestinal illness (27 patients, 8.4%); nausea and vomiting (24, 7.5%); dizziness (12, 3.8%); drowsiness and mental confusion (eight, 2.5%); voiding difficulty (seven, 2.2%); skin reaction (five, 0.6%); and others (31, 9.7%).

Malignancy (OR=0.305, 95% CI: 0.145 to 0.642) and prescription duration (OR=2.127, 95% CI: 1.137 to 3.980) were significant variables in opioid type. The occurrence rate of adverse reactions of morphine and that of oxycodone were 7.3 times (95% CI: 2.545 to 20.701) and 7.5 times (95% CI: 2.547 to 22.208) greater than that of codeine. In concurrent administration of two or more opioids, malignancy (OR=0.323, 95% CI: 0.169 to 0.617), prescription duration (OR=2.054, 95% CI: 1.149 to 3.673) and GABA analogue (OR=3.259, 95% CI: 1.777 to 5.977) were significant. The occurrence rate of adverse reactions of concurrent administration of two or more opioids was approximately 2.8 times (95% CI: 1.089 to 7.163) greater than that of a single opioid drug.

Conclusion In elderly male patients with opioid administration, factors that affected relatively lower development of adverse reactions were malignancy and codeine. Administrations of long-term opioids, concurrent GABA analogue and multiple opioids increase adverse reactions.

References and/or acknowledgements Thanks to our head of the pharmacy department and hospital officials who have extended helping hands for this study.

No conflict of interest.