The prior intake of oral opioids is no contraindication to switch to a transdermal patch because conversion from the oral to the transdermal opioid can be easily achieved by the use of a conversion table, always keeping in mind to adapt to the individual reaction by means of up- or down dosing. Therefore, careful and adequate titration of the dosage is the most relevant factor for a successful transition. Dose titration is determined by the need of the patient when switching from oral morphine to transdermal fentanyl:
1. Calculate the usual oral dose of morphine per 24 h.
2. By using a conversion scale for rough calculation of oral morphine to transdermal fentanyl.
3. Calculate the equianalgesic dosage of fentanyl TTS using the necessary dose of oral morphine per 24 h (Table IV-11).
4. Realize that short-term dose adaptation of the opioid dose is not possible when using the transdermal route of application. Therefore only patients with a stable pain level should be considered as possible candidates for a transdermal medication.
5. The lowest dose of the transdermal patch should be used as the initial dose. Consideration should be given to the previous opioid history of the patient as well as to the current general condition and medical status of the patient. The dose should not be increased before 3 days, when the maximum effect of a given dose is established. Subsequent dosage increases may then be titrated based on the need for supplemental pain relief and the patient's analgesic response to the patch.
Table IV-11. Conversion scale switching from oral morphine to transdermal fentanyl
Oral morphine Fentanyl TTS Size of patch
91-150 50 20
151-210 75 30
210-270 100 40
Each 60 mg/day Each 25 /u,g/h Each 10 cm2
6. To increase the dose, a larger patch should replace the patch that is currently being worn, or a combination of patches should be applied in different places to achieve the desired dose. It is recommended that no more than two patches are applied at the same time, regardless of the patch strength. A new patch should not be applied to the same skin site for the subsequent 3-4 weeks. Patients should be carefully and regularly monitored to assess the optimum dose and duration of treatment.
7. Similar as in oral opioid therapy with slow release morphine, consider the possibility of breakthrough pain, and have a rescue medication available [30, 54].
8. For rescue medication of breakthrough pain, either morphine immediate release (MIR), the effervescent morphine tablet (Painbreak®), or the oral transmucosal fentanyl stick (OTFS) Actiq® is advocated.
9. While tumor pain patients should be given an opioid for rescue medication, patients with non-malignant pain should be given an NSAID.
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