hydromorphone
Meaning of hydromorphone: Potency is both the point and the hazard, since a quantity that would suit morphine is far too much of this drug.
Definition of hydromorphone
Hydromorphone is a strong opioid painkiller used for moderate to severe pain that milder analgesics have not controlled. It is produced by chemically modifying morphine, and it acts on the same opioid receptors in the brain and spinal cord that dull the perception of pain. Weight for weight it is several times more potent than morphine itself.
How does it relieve pain?
Pain signals travel from the site of injury up the spinal cord to the brain. Hydromorphone attaches to receptors along that route, mainly in the spinal cord and in the brain regions that register and interpret pain. Binding there reduces the transmission of the signal and, just as importantly, changes how the brain responds to what does arrive, so pain becomes less distressing as well as less intense. The same receptors sit in the brainstem centers that control breathing and in the wall of the intestine, which is why slowed breathing and constipation follow from the identical mechanism rather than being unrelated side effects.
Why does potency matter so much?
| Hydromorphone | Morphine | |
|---|---|---|
| Relative strength by weight | Several times greater | The reference point |
| Usual quantity | Small | Larger for the same effect |
| Consequence of an error | A given error in quantity carries more effect | Comparatively less |
Because the numbers are small, an error of a single decimal place has a much larger consequence than the same slip with a weaker opioid. Conversion between opioids relies on published equivalence tables, and those figures are approximations that vary with the route and with how long a person has been taking the previous drug, so a converted dose is a starting estimate rather than an equivalent.
What comes with it?
Drowsiness, nausea, itching and difficulty passing urine are common early on, and most of these ease as tolerance develops. Constipation does not ease, because the gut does not adapt in the way the brain does. Slowed breathing is the effect that defines the ceiling of any opioid, and it is deepened by alcohol and by sedatives taken at the same time. With continued use the body becomes physically dependent, so stopping abruptly brings withdrawal, which is a separate matter from addiction. Hydromorphone is regulated as a controlled substance, and it is used both for pain after surgery and for pain associated with serious illness.
Also known as
Used in a sentence
Hydromorphone was ordered for breakthrough pain that persisted despite the patient's scheduled opioid regimen.
Good to know
Hydromorphone is considerably more potent by weight than morphine, so equivalence tables used when converting between the two give approximate starting figures rather than equal quantities.