Jack Smith is a terminally ill lung cancer patient. Jack Smith's
current pain medication is oxycontin 40mg q 8 hours. Please convert it into
an equianalgesic dose of parenteral hydromorphone.
Step 1
First determine total 24 hour dose of current drug. The total dose
is the product of the unit dose in milligrams and the frequency of administration.
Current unit dose
= 40 milligrams
Current frequency
= 3
(pt gets the drug every eight hours which is 3 times in 24 hours)
24 hour total dose of oxycodone
= Unit dose in milligrams x Frequency
Current 24 hour total dose of oxycodone
= 40mg x 3 = 120mg
Step 2
Convert total 24 hour dose of current drug to equianalgesic dose of
ORAL morphine using the following guidelines:
24 hour dose of current drug in milligrams
Conversion ratio to ORAL morphine
Equivalent dose of ORAL morphine
60mg of parenteral morphine
Parenteral morphine is three times as potent as oral morphine
180 milli grams Oral morphine
120 mg of oral oxycodone
Oral Oxycodone is roughly 1.5 times more potent than oral morphine
180 milli grams Oral morphine
45 mg of oral hydromorphone
Oral hydromorphone is 4-7 times as potent as oral morphine
180 milli grams Oral morphine
9mg of parenteral hydromorphone
Parenteral hydromorphone is 20 times as potent as oral morphine
180 milli grams Oral morphine
45mg of oral hydrocodon
Oral hydromorphone is roughly five times as potent as oral morphine
(4 to 7 times more potent)
180 milli grams Oral morphine
1800 micrograms (1.8 milligrams) over 24 hours. Therefore hourly
dose is 75 micrograms/hour.
Transdermal fentanyl is 100 times as potent as morphine
180 milli grams Oral morphine
Current 24 hour total dose of oxycodone
= 40mg x 3
= 120mg
Oral Oxycodone is roughly 1.5 times more potent than
oral morphine.
Therefore, equianalgesic dose of oral morphine
= oxycodone dose in milligrams x 1.5
= 120mg x 1.5
= 180mg of oral morphine
Step 3
Convert the calculated 24 hour equianalgesic dose of oral morphine
to the 24 hour equianalgesic dose of the new opioid:
Calculated 24 hour equianalgesic dose of oral morphine
= 180mg
Parenteral hydromorphone is 20 times as strong as oral
morphine.
Therefore 180mg of oral morphine
= 180/ 20 mg of parenteral hydromorphone
= 9mg of parenteral hydromorphone
Step 4
Divide the 24 hour dose of the equianalgesic dose of
the new opioid to determine the unit doses and frequency:
Jack Smith is a terminally ill lung cancer patient. Jack Smith's current
pain medication is Morphine sulfate sustained release 45mg every 12 hours.
During a clinic visit, Mrs. Smith complains that she has noticed that her
husband has developed muscle twitching ever since his Morphine sulfate sustained
release was increased to 45mg every 12 hours. You review Mr. Smith's recent
chemistry panel and note that his creatinine is elevated at 2.4. Please
convert the transdermal fentanyl into an equianalgesic dose of long acting
oxycodone.
Sequential steps
Sequential steps
Process
Answer
First determine total 24 hour dose of current drug.
The total dose is the product of the unit dose in milligrams
and the frequency of administration in 24 hours.
In this case:
Unit dose = 45mg
Frequency of administration = 2 times in 24 hours
Therefore total dose = Unit dose x frequency = 45 x 2= 90mg
Patient is currently on 90mg of Morphine sulphate.
Convert total 24 hour dose of current drug to equianalgesic dose
of ORAL morphine.
Current drug in this case is Morphine sulfate.
4 hour equianalgesic dose = 90mg of morphine sulfate.
Convert the calculated 24 hour equianalgesic dose of oral morphine
to the 24 hour equianalgesic dose of the new opioid.
Oxycodone is the preferred drug in this case as it is renally safer
than morphine. Oxycodone is thought to be 1.5 times stronger than
morphine.
Therefore, Morphine sulfate 90mg is equianalgesic to oxycodone 60mg
24 hour equianalgesic dose of the new opioid (oxycodone) = 60mg
Divide the 24 hour dose of the equianalgesic dose of the new opioid
to determine the unit doses and frequency.
Similar to morphine, oxycodone is available in a sustained acting
preparation Oxycodone (OxyContin™) that can be dosed every
12 hours. In this case Oxycodone 60mg in 24 hours can be divided
into a unit dose of 30mg to be given every 12 hours.
Final order for basal analgesic should read:
Oxycodone sustained release every 12 hours for chronic pain.
