How clonidine works
Clonidine lowers the release of the messenger substances of the sympathetic nervous system, adrenaline and noradrenaline, by activating alpha-2 receptors (docking sites). The end result is a reduction in blood pressure and heart rate, minor sedation, and pain relief.
Clonidine is a so-called antisympathotonic (inhibits the action of the sympathetic nervous system). The sympathetic nervous system is that part of the autonomic nervous system which, with the help of the “stress hormones” adrenaline and noradrenaline, puts the body into an increased state of readiness to perform – i.e. triggers bodily reactions such as a rapid heartbeat, a widening of the bronchial tubes (better oxygen intake) and an increase in blood pressure.
This state is also called “fight or flight” mode. The counterpart to the sympathetic nervous system is the parasympathetic nervous system. It ensures the regeneration of the body and promotes digestion, which is why it is also called “rest and digest” mode.
Other effects of the drug, such as lowering vascular resistance, are mediated via stimulation of imidazole receptors. Clonidine is also used to treat attention deficit hyperactivity disorder (ADHD). However, the exact mechanism of action is not known.
Absorption, degradation and excretion
After ingestion as a tablet, clonidine is well absorbed into the blood through the intestinal wall and reaches its maximum blood level after one to three hours. In the liver, a small portion of the ingested drug is broken down by enzymes.
After about eight to eleven hours, three-quarters of the administered amount of clonidine is excreted in the urine and one-quarter in the stool.
When is clonidine used?
The indications for use (indications) of clonidine are:
- High blood pressure (hypertension)
- Hypertensive crises in intensive care (intravenous administration).
- Adjunctive in analgesia (combined administration of sedatives and analgesics).
- Withdrawal symptoms in the treatment of drug or alcohol addiction
- Glaucoma (in the form of eye drops)
- ADHD
Typically, use is for longer periods of time.
How clonidine is used
Generally, clonidine is taken in the form of tablets or capsules, especially for the treatment of hypertension. At the beginning of treatment, the dosage is slowly increased until the individually required dose is found.
This procedure is also called “creeping dosage”. Another advantage of this slow increase in dosage is that it prevents sharp drops in blood pressure, which can be felt as dizziness or weakness.
