To convert the dosage of one opioid to an equivalent dose of another opioid, the following formula is useful:
By substituting the appropriate values, it is possible to solve the equation to find the Dose of the New Medication.
A table of Conversion values is listed below.
To view this table graphically,
click here:
| Drug Name |
IV
Conversion Factor |
PO
Conversion Factor |
| Morphine |
10 mg
|
30
mg
|
| Fentanyl |
0.2 mg
(200 mcg)
|
|
| Hydromorphone |
2 mg
|
8
mg
|
| Demerol |
100 mg
|
300
mg
|
| Methadone |
10 mg
|
20
mg
|
| Oxycodone |
-
|
30
mg
|
| Oxymorphone |
1 mg
|
-
|
| Codeine |
75 mg
|
130
mg
|
| Hydrocodone |
|
30
mg
|
| Propoxyphene |
|
60
mg
|
| Heroin |
5 mg
|
|
| Levorphanol |
2 mg
|
4
mg
|
| Butorphanol |
2 mg
|
|
| Buprenorphine |
0.4 mg
|
|
| Talwin |
60 mg
|
160
mg
|
As an example, 75 mg of PO Morphine is converted to IV Fentanyl below:
[Current Dose]/[Current Conv factor] = [Desired Dose]/[Desired Drug Factor]
75 mg/30 mg = [Fentanyl dose]/[0.2mg]
[Fentanyl dose]= (75/30)*0.2=0.5 mg
Notes:
1. The units of Fentanyl are in the same units as the conversion factor for Fentanyl, i.e. mg. Had 200 mcg been used as the conversion factor, the dose would have been in mcg as well (500 mcg).
2. If the original Morphine dose was for a full day, the computed Fentanyl dose would also be for the full day. Therefore to calculate an hourly rate, it is necessary to divide 500mcg by 24 = 20.8 mcg/hr. Likewise, if the original dose of Morphine applied only for 8 hours, so too would the computed Fentanyl dose.
3. Different authors advocate different conversion factors. The above formula will be correct using other conversion factors.
4. If you have a Palm Compatible device. Click here for a downloadable Palm application called Pain Stat. Note that it uses conversion factors different from the above values.
To practice and check your calculations, try the interactive converter.
Last Updated: September 30, 2001 5:18 PM