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Changing opioids
We have already looked at some of the reasons for switching between strong opioids - if patients have poor renal function, experience heavy sedation or develop some of the less common side effects.
Another common reason to change is if patients are unable to comply with the medication - because they are too frail, confused or if they are unable to swallow. In these cases, patients may benefit from changing the route of administration. Analgesia can be given by continuous subcutaneous infusion via a syringe driver, or transdermally via a patch.
Whatever the route or opioid used, it is important to consider the correct conversion to ensure adequate pain relief continues.
Table 1 lists common opioids (and routes) used as alternatives to oral morphine, with the equivalent dose compared to oral morphine.
Drug |
Dose |
Route |
|---|---|---|
Morphine |
10mg |
oral |
| Morphine | 5mg | subcutaneous / intramuscular |
Diamorphine |
3mg |
subcutaneous / intramuscular |
Hydromorphone hydrochloride |
1.3mg |
oral |
Oxycodone |
6.6mg |
oral |
Transdermal fentanyl preparations are sometimes used for patients having problems taking oral morphine. The patches come in fixed sizes, and the equivalent oral morphine doses are shown below.
24 hour oral morphine |
Equivalent Fentanyl dose (every 72 hours) |
|---|---|
90mg |
25 micrograms/hour (Fentanyl 25 patch) |
180mg |
50 micrograms/hour (Fentanyl 50 patch) |
270mg |
75 micrograms/hour (Fentanyl 75 patch) |
360mg |
100 micrograms/hour (Fentanyl 100 patch) |