Comparing Long-Acting Opioids

Dean L.

Publication Details

Opioids are natural derivatives of morphine and are powerful painkillers that can treat most types of severe pain. Their side effects are varied and include abuse and addiction.

Long-acting opioids are those given 3 times a day or less frequently. They are commonly used to treat chronic pain, which is pain that lasts for at least 3 to 6 months. An estimated 1 in 5 Americans experience chronic pain.

The "Drug Class Review: Long-Acting Opioid Analgesics" compares the safety and effectiveness of eleven long-acting opioids. A summary of the findings is below.

How do long-acting opioids compare in treating chronic non-cancer pain?

Overall, there is insufficient evidence to determine whether one long-acting opioid is superior to another in either relieving pain or improving function and helping individuals to return to normal daily activities. Eight of ten trials that directly compared two or more long-acting opioids in adults with non-cancer pain found no significant differences. Two trials that did report differences were rated as poor quality, meaning their results are likely to be due to flaws in the studies rather than true differences between the drugs. [full review]

It is also not clear whether long-acting opioids are more effective than short-acting opioids. Seven fair-quality trials found no significant differences in outcome between long- and short-acting opioids, but the studies differed in their populations, doses of the drugs used and other factors, making generalizations difficult. For the drug oxycodone, three similar trials found that long-acting and short-acting forms were equally effective for pain control. [full review]

How do long-acting opioids compare in safety?

Adverse effects of opioids include nausea, vomiting, constipation, dizziness, drowsiness, confusion, addiction and abuse.

Currently, there is insufficient evidence to conclude that one long-acting opioid is safer than another, especially regarding the risk of abuse and addiction. It is also not possible to conclude whether long-acting opioids are any safer than their short-acting counterparts.

Compared to long-acting morphine, transdermal fentanyl is associated with a lower risk of constipation, but it is also associated with more people withdrawing from trials because of any adverse event. [full review]

Does age or ethnicity influence the safety or effectiveness of long-acting opioids?

One study found that in individuals older than 65, the risk of constipation was higher for long-acting oxycodone than transdermal fentanyl. There is almost no other information regarding how long-acting opioids compare in individuals of different age, gender, race, or in patients who have different types of chronic non-cancer pain. [full review]

Drugs included in this review

Further Information

Image th-derp.jpgThis PubMed Clinical Q&A was reviewed by Susan Carson, MPH.

For the full report and evidence tables, please see:
Carson S, Thakurta S, Low A, et al. Drug Class Review: Long-acting opioid analgesics. [Internet]. Portland (OR): Oregon Health & Science University; 2011 July. Available at