papaverine
Meaning of papaverine: An opium poppy compound that relaxes blood vessels and hollow organs without relieving pain or causing addiction.
Definition of papaverine
Papaverine is a compound obtained from the opium poppy and also made synthetically, used to relax smooth muscle and widen blood vessels. Although it comes from the same plant as morphine, it does not relieve pain, does not cause sedation and does not act on opioid receptors. It works instead by blocking enzymes inside the muscle cell, which allows the vessel wall to slacken.
How does it relax muscle?
Smooth muscle lines blood vessels, airways, the gut and the urinary tract, and it contracts without conscious control. Papaverine blocks phosphodiesterase, the enzyme that destroys the internal signaling molecules telling a muscle cell to relax. With that signal preserved, the cell stays relaxed. It also interferes with the movement of calcium into the cell, and calcium is what triggers contraction. Both effects push in the same direction, and the muscle slackens, widening whatever tube it surrounds.
Where is it used?
| Use | What it achieves |
|---|---|
| Injection into the penis | Widens the vessels to produce an erection |
| Applied during vascular surgery | Relieves spasm in a vessel being handled |
| Given into an artery | Counters spasm of arteries around the brain |
| Cramping of the gut or bile ducts | An older use, largely superseded |
How does it differ from other opium alkaloids?
The poppy yields several distinct compounds, and structure sorts them into groups that behave nothing alike. Morphine and codeine are phenanthrene alkaloids and act on opioid receptors, giving pain relief along with drowsiness, constipation and the potential for dependence. Papaverine belongs to a different chemical family entirely and reaches none of those receptors. It is therefore not an opiate in the pharmacological sense, only in the botanical one. Because of that shared origin it is still listed in some regulations alongside controlled substances, which is a matter of source rather than of effect.
What are its drawbacks?
Given into a vein too quickly it can disturb heart rhythm and drop blood pressure sharply. Liver inflammation has been reported with prolonged use, showing as raised liver enzymes. Where it is injected locally for erectile problems, a prolonged and painful erection is the recognized hazard, and scarring of the tissue can develop with repeated use. Newer drugs that block a single specific form of the same enzyme family have replaced it for most everyday purposes.
Used in a sentence
Papaverine was applied topically to relieve arterial spasm during the graft anastomosis.
Good to know
Papaverine shares a botanical source with morphine but not its pharmacology, having no opioid receptor activity, no analgesic effect and no dependence liability.
Word origin
Where “papaverine” comes from
From the Latin papaver, meaning poppy, the plant from which the compound was first isolated.