After his Specialist Nurse prescribed his morphine, Terry’s pain has been well controlled. At first he did feel a bit nauseous but that soon wore off. He didn’t need any oramorph for 2 weeks and had even gone on a few short outings with his walking group.
A month later, the GP telephones him to review his opioids. Terry says his pain is manageable but he has needed to take morphine IR liquid for breakthrough pain (BTP). The BTP is usually worse in the morning and in the evening. This suggests that Terry’s dose of MR morphine (often termed “background analgesia”) needs to be increased.
The process for doing this is similar to that for initiating a strong opioid.
First the total amount of opioid consumed in 24 hours is calculated
- This dose is divided by 2 to calculate the new 12 hourly dose of MR morphine.
- This dose increase should not exceed 50% of the previous dose.
- If this is the case, specialist advice must be sought.
Next the dose of rescue IR opioid is calculated
- This is done by dividing the total amount of opioid (IR plus MR) taken in 24 hours by 6.
- Remember to round all doses up or down to the most practical available.
If your patient is already taking a weak opioid this must be converted to an equivalent dose of morphine.
- The equivalent amount taken in 24 hours calculated.
- As a general rule, morphine is ten times more potent than codeine.
- The total dose of codeine taken in 24 hours is thus divided by 10.
- Background and breakthrough opioid doses are then calculated in the usual way from this figure.
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