Surprisingly, little is known about the long-term effects of opioid analgesics; most of the literature that exists discusses the effects of chronic opioid use in individuals with persistent pain (Pasero, Quinn, Portenoy, McCaffery, & Rizos, 2011). The effect of opioids on immune function has been studied in animals and in humans in the absence of pain and has been found to suppress immune function; however, in the presence of acute pain, opioid administration in analgesic doses seems to be protective (Page, 2005). Much less is known about the effect on the immune system of prolonged opioid administration in the presence of persistent pain. It is well known that pain itself suppresses immune function; opioids in analgesic doses could provide relief of pain and thereby provide some relief of the immune suppression of pain (Page, 2005).
Negative effects of opioids on the endocrine system have been known for years, but little has been written about this (Pasero, Quinn, Portenoy, McCaffery, & Rizos, 2011). Most of the literature concerns opioid-induced hypogonadism, which is probably common in both male and female patients on long-term opioid therapy (Katz & Mazer, 2009). No standards for laboratory monitoring exist, but recommendations include testing for total and free testosterone (especially in men) and monitoring bone density. Symptoms include decreased libido, erectile dysfunction in men, depression, anxiety, and fatigue. Of course, these symptoms may be due to many other causes, such as pain itself. Treatment considerations include opioid rotation (switching to another opioid) and testosterone supplementation. Based on available information, it is not reasonable to withhold opioid therapy because of concerns about endocrine effects of long-term opioid use. These can be monitored and treated.