HYDROmorphone vs. Morphine
HYDROmorphone and morphine both belong to the class of medications called opioid analgesics. Opioid analgesics work by interacting with one or more sub types of opioid receptors (mu, delta, kappa, sigma, epsilon) at either the supraspinal, spinal or peripheral levels.
Both HYDROmorphone and morphine work on multiple pathways. They are both considered to be full agonists at the mu opioid receptors, and the agonistic activity leads to pain relief. By acting on the mu opioid receptors, HYDROmorphone and morphine inhibit the release of excitatory neurotransimitters that relay pain signals from the site of injury to the brain. Therefore, HYDROmorphone and morphine modify the patient's perception of pain signals, giving the patient a period of pain relief after the drug has been administered.
Adverse Effects
Both HYDROmorphone and morphine exhibit similar side effects because they work on similar receptors. The side effects occur because of the ability of these drugs to work on different receptors in different areas of the body. The following is a list of the most common side effects with a brief explanation about why these side effects occur:
In addition to these common side effects, HYDROmorphone and morphine may also cause respiratory depression and cardiac depression/arrest when they significantly slow down the body's respiratory and cardiovascular and systems (especially in overdose situations).
Tolerance and dependence to HYDROmorphone and morphine (and other opioid analgesics) may also develop through use of these medications over time. Both of these situations may arise due to continued use of opioid analgesics overtime, but are not an indication of addiction.
Tolerance is defined as a state of adaptation in which exposure to the drug results in a reduced response to the drug effects over time. Therefore, a patient who becomes tolerant to an opioid drug will require more of the drug in order to achieve a similar extent of pain relief. Additionally, a patient may develop tolerance to side effects over time due to continued exposure to the drug.
Dependence is defined as a state of adaptation in which withdrawal syndromes may be produced if the dose of the opioid drug is abruptly reduced, if blood levels for the drug are reduced and/or if effects of the drug in the blood are antagonized by an opposing drug. Therefore, a patient who is dependent on an opioid drug will develop withdrawal symptoms if doses are missed or reduced abruptly
Addiction to an opioid drug involved psychosocial, environmental and physiologic factors that lead to a change in a patient's behavior leading to cravings or compulsive use of the drug despite knowledge that the use of the drug is associated with harm.
- Itchiness - occurs due to histamine release from mast cells
- Nausea/vomiting - occurs due to effects in the chemoreceptor trigger zone in the brain
- Drowsiness and sedation - occurs due to depression of higher CNS centers in the brain
- Constipation - occurs due to activity in the intestines and the slowing down of gut motility
In addition to these common side effects, HYDROmorphone and morphine may also cause respiratory depression and cardiac depression/arrest when they significantly slow down the body's respiratory and cardiovascular and systems (especially in overdose situations).
Tolerance and dependence to HYDROmorphone and morphine (and other opioid analgesics) may also develop through use of these medications over time. Both of these situations may arise due to continued use of opioid analgesics overtime, but are not an indication of addiction.
Tolerance is defined as a state of adaptation in which exposure to the drug results in a reduced response to the drug effects over time. Therefore, a patient who becomes tolerant to an opioid drug will require more of the drug in order to achieve a similar extent of pain relief. Additionally, a patient may develop tolerance to side effects over time due to continued exposure to the drug.
Dependence is defined as a state of adaptation in which withdrawal syndromes may be produced if the dose of the opioid drug is abruptly reduced, if blood levels for the drug are reduced and/or if effects of the drug in the blood are antagonized by an opposing drug. Therefore, a patient who is dependent on an opioid drug will develop withdrawal symptoms if doses are missed or reduced abruptly
Addiction to an opioid drug involved psychosocial, environmental and physiologic factors that lead to a change in a patient's behavior leading to cravings or compulsive use of the drug despite knowledge that the use of the drug is associated with harm.
Key Differences Between HYDROmorphone and Morphine
It is important to remember that HYDROmorphone and morphine are NOT the same drug and are NOT equivalent in dosing.
HYDROmorphone is approximately 5 times more potent than morphine.
That is, HYDROmorphone is approximately 5 times stronger than morphine. You may also find that some sources will mention HYDROmorphone is 4 to 7 times more potent than morphine. The key message is they HYDROmorphone is the stronger of the two, and a mix-up between these two medications can lead to detrimental consequences!
Since HYDROmorphone is approximately 5 times more potent than morphine, you will notice that an equivalent dose of morphine will be larger in comparison to the HYDROmorphone dose. The following examples demonstrate the difference in dosing during dose conversions:
e.g. morphine 2 mg IV q2h PRN pain
This is approximately equivalent to HYDROmorphone 0.4 mg IV q2h PRN pain
(0.4 mg x 5 = 2 mg)
e.g. HYDROmorphone 5 mg PO q4h PRN pain
This is approximately equivalent to morphine 30 mg PO q4h PRN pain
(30 mg / 5 = 6 mg)
An easy memory aid to help you remember this potency difference was presented in the symposium. Below you will find an explanation of this memory aid.
Since HYDROmorphone is approximately 5 times more potent than morphine, you will notice that an equivalent dose of morphine will be larger in comparison to the HYDROmorphone dose. The following examples demonstrate the difference in dosing during dose conversions:
e.g. morphine 2 mg IV q2h PRN pain
This is approximately equivalent to HYDROmorphone 0.4 mg IV q2h PRN pain
(0.4 mg x 5 = 2 mg)
e.g. HYDROmorphone 5 mg PO q4h PRN pain
This is approximately equivalent to morphine 30 mg PO q4h PRN pain
(30 mg / 5 = 6 mg)
An easy memory aid to help you remember this potency difference was presented in the symposium. Below you will find an explanation of this memory aid.
MEMORY AID
The drug name HYDROmorphone and the word "horse" both start with the letter "H," and the drug name morphine and the word "mouse" both start with the letter "M." If you can remember that a horse is bigger and stronger than a mouse, then you will always remember that HYDROmorphone is always stronger than morphine!
HYDROmorphone/Morphine Event
On June 6, 2004, a patient at XXX Hospital accidentally received HYDROmorphone instead of morphine which resulted in a fatal overdose. The Institute for Safe Medication Practices Canada (ISMP Canada) conducted an Event Analysis Report to investigate the event and identify system-based root causes to make recommendations about strategies to prevent similar events in the future. The full Event Analysis Report can be found in the Resources and Links section of this web site. The recommendations that were made by ISMP Canada to prevent similar events can be found in the Safety Initiatives section of this web site. Below you will find a short documentary that was put together to explain the details that lead to the fatal incident.
1. DiPiro JT, Talbert RL, Yee GC, et al. Pharmacotherapy: A Pathophysiologic Approach. 7th Ed. Chapter 62: Pain Management. New
York. McGraw-Hill Companies; 2008.
2. ISMP Canada Safety Bulletin. Identifying knowledge deficits related to HYDROmorphone. June 27, 2012. Available at:
http://www.ismp-canada.org/download/safetyBulletins/2012/ISMPCSB2012-07_IdentifyingKnowledgeDeficits-
HYDROmorphone.pdf. Accessed February 18, 2013.
3. Kalant H, Grant DM, Mitchell J. Principles of Medical Pharmacology. 7th Edition. Toronto, Canada. Elsevier; 2007.
4. PA PSRS Patient Saf Advis 2007 Sep;4(3):89.