Migraine Quiz

Hidden Pitfalls of Opiates

Common side-effects of opiate analgesics

Opioid analgesics, which are also commonly called narcotics or opiates, are derived from the medicinal poppy and have been with us for centuries as a means of relieving pain. Only recently have we begun to unravel some of the deeper secrets of exactly how these medications may affect us at a cellular level.

The more common side effects of these painkillers are probably pretty well-known to most who have taken these medications: constipation, sedation, itchiness, urinary retention, nausea, and respiratory depression. What you may not know about is some of the less commonly discussed side effects of these commonly used pain medications.

One of the problems associated with opioid medications is suppression of the immune system. A variety of studies have found that chronic use of these medications is strongly associated with increased risk of infection or worsening or existing infection. This has been found to be true for both bacterial infections and for HIV/AIDS.

Another problem that can occur is called opioid-induced hyperalgesia. When this happens, pain increases despite increasing doses of opiate painkillers. This occurs because of chronic narcotic medication use, and occurs independently of allodynia. (Allodynia means you feel pain from touch or other stimulus which would not be painful normally.)

Less usual side-effects of painkillers

Chronic use of opioids can also result in hormonal imbalance, known in technical terms as hypogonadal hypogonadism. In men, this results in fatigue, depression, anemia, decreased libido, erectile dysfunction, and bone loss (osteopenia). This affects most men who are on a chronic opioid regimen or on methadone maintenance. This hormonal imbalance can also affect women, and results in fatigue, depression, anemia, decreased libido, menstrual and ovulatory difficulties, and bone loss.

In a few alarming studies, there is some evidence to suggest that there may be some effect of opioids to accelerate growth of some tumor types. Further follow-up studies are underway to confirm this possibility.

A new class of medications has been developed to combat some of the side-effects of opioids. These peripherally-acting mu-opioid receptor antagonists (PAMORAs for short) work outside the brain to block many of the more common side effects of opioids—and a few of the less common ones. The PAMORAs were developed to combat opioid-related constipation. Recent research suggests that they might have some ability to suppress viral activity in HIV and Hepatitis C, and to prevent the development of certain bacterial infections in ICU patients, although this very preliminary. Further studies are needed.

PAMORAs may also have the ability to block the tendency of opioids to promote the spread of tumor cells. Again, further research into this is in process. Will PAMORAs have a role beyond treating opioid-induced constipation? It’s far too early to tell. For now, though, you are more informed about opioids.

references

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4. Wei G, Moss J, Yuan CS. Opioid-induced immunosuppression: is it centrally mediated or peripherally mediated? . Biochem. Pharmacol. 2003 Jun 1;65(11):1761-1766.[cited 2009 May 12] Available from: http://www.ncbi.nlm.nih.gov/pubmed/12781327

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6. Weber RJ, Pert A. The periaqueductal gray matter mediates opiate-induced immunosuppression. Science. 1989 Jul 14;245(4914):188-190.[cited 2009 May 12] Available from: http://www.ncbi.nlm.nih.gov/pubmed/2749256

7. Moss J, Rosow CE. Development of peripheral opioid antagonists' new insights into opioid effects. Mayo Clin. Proc. 2008 Oct ;83(10):1116-1130.[cited 2009 May 12] Available from: http://www.mayoclinicproceedings.com/content/83/10/1116.long