Catapres
Meaning of Catapres: A blood pressure tablet that works from inside the brain, quieting the nerve traffic that keeps vessels tight.
Definition of Catapres
Catapres is a brand name for clonidine, a medicine that lowers blood pressure by acting on receptors in the brainstem. Stimulating those receptors reduces the outgoing nerve signals that keep blood vessels narrowed and the heart driven, so vessels relax and the heart slows. The same effect on nerve traffic explains its other uses, which range from hot flashes to withdrawal symptoms.
How does it lower blood pressure?
Most blood pressure drugs act on the vessels, the kidney or the heart. This one acts on the control center. Nerves running out from the brainstem set the background tension in artery walls by releasing noradrenaline at their endings. Clonidine stimulates a receptor on those nerves that functions as a brake, and less noradrenaline is released. Vessels widen, the heart rate falls, and blood pressure follows. The mechanism is the reverse of a stimulant, which explains why drowsiness and a dry mouth are its most familiar unwanted effects.
What else is it used for?
| Use | What it addresses |
|---|---|
| Attention deficit hyperactivity disorder | Impulsivity and difficulty settling, often with sleep problems |
| Tic disorders | Frequency and intensity of tics |
| Opioid and alcohol withdrawal | Sweating, agitation, racing pulse and cramping |
| Menopausal flushing | Hot flashes, including where hormone treatment is unsuitable |
| Severe pain | Given into the space around the spinal cord alongside opioids |
Why does stopping it suddenly matter?
The body adapts to the suppressed nerve traffic by becoming more sensitive to noradrenaline. If the drug is withdrawn abruptly, that suppression lifts while the heightened sensitivity remains, and pressure can rebound higher than it was to begin with, accompanied by agitation, sweating and a racing pulse. The reaction is well documented and is the reason the drug is tapered rather than stopped outright. Missed doses can produce a milder version of the same thing.
What does it feel like to take?
Drowsiness and a dry mouth are common at the start and often ease over weeks. Constipation, low mood and dizziness on standing occur, the last because the usual reflex tightening of vessels on rising is blunted. Because sedation is part of the effect rather than an accident of it, the sleepiness tends to be dose related. Patch and tablet forms exist, and the patch delivers a steadier level over several days.
Also known as
Used in a sentence
Catapres was tapered over two weeks rather than discontinued outright.
Good to know
Abrupt withdrawal of clonidine can produce rebound hypertension with agitation and a racing pulse, which is why the dose is reduced gradually rather than stopped at once.