Opioids Available in Rectal Suppository Formulations
Morphine and oxycodone are the primary opioids available as rectal suppositories, with morphine being the most widely used and best-studied option for rectal administration. 1
Primary Opioid Suppositories
Morphine
- Morphine is available in rectal suppository form with a 1:1 bioavailability ratio compared to oral administration, meaning the same dose can be used rectally as would be given orally 1, 2
- The duration of analgesia is equivalent between oral and rectal routes 1
- Rectal morphine demonstrates rapid onset of action, achieving significant pain reduction at 10 minutes compared to 60 minutes for oral administration 3
- Only immediate-release morphine formulations should be used rectally—never crush controlled-release tablets for rectal administration 1, 2
- Rectal morphine is safe, effective, inexpensive, and particularly useful when rescue doses are needed in patients on regular oral or parenteral opioids 3
Oxycodone
- Oxycodone has historically been available as a rectal suppository formulation, particularly in low-dose combination products 1
- It has been used for treating both post-operative pain and cancer pain via the rectal route 1
- Oxycodone's better systemic bioavailability (60-90%) makes it an effective alternative when morphine is not tolerated 1
Oxymorphone
- Oxymorphone is available as a rectal suppository, though it is substantially less potent via this route compared to intramuscular administration 4
- Rectal oxymorphone is approximately 1/10 as potent as intramuscular oxymorphone when considering total analgesic effect 4
- Doses of 5-10 mg oxymorphone by suppository provide analgesia comparable to usual doses of parenteral narcotics 4
- The rectal route produces lower and more delayed peak analgesia but longer duration of action compared to intramuscular administration 4
Clinical Context for Rectal Administration
When to Use Rectal Opioids
- Rectal administration is the preferred alternative route when patients cannot take oral medications, alongside subcutaneous administration 1, 2
- Particularly useful in pediatric postoperative pain management when combined with NSAIDs and acetaminophen 1
- Effective for breakthrough pain management when oral routes are unavailable 3
Practical Considerations
- The rectal route is acceptable to patients and is probably underutilized by physicians in controlling moderate to severe pain 4
- Liquid morphine solutions (microenemas) are well absorbed rectally and offer rapid onset of action 3
- Rectal administration produces comparable side effects to equivalent doses given by other routes 4, 3
Important Caveats
- Tramadol is also mentioned as available in rectal formulation for pediatric postoperative pain management, though it is technically a weaker opioid 1
- Hydromorphone is available in suppository formulations according to some guidelines, providing an alternative to morphine 1
- The rectal route may not be appropriate for all patients depending on local disease, patient preference, or anatomical considerations 5