Clonidine is an alpha 2 adrenergic agonist that is used to treat a variety of conditions and diseases like hypertension, ADHD, Tourette's syndrome or human growth hormone deficiency. Alpha 2 adrenergic receptors exist on the presynaptic neuron membrane and act as a negative feedback mechanism to stop the release of neurotransmitters like norepinephrine from being released. Norepinephrine released binds to alpha 1 and beta 1 adrenergic receptors on muscle tissues or post synaptic neurons to elicit different g-protein signalling cascades with can lead to increased calcium release from cell storage. Increased calcium release promotes muscle contraction. By clonidine inhibiting the release of norepinephrine through negative feedback, less is release and therefore less muscle contraction is elicited. In cardiac muscle, less norepinephrine allows arteries to relax lowering blood pressure. Clonidine is taken orally or transdermally and is absorbed in the bloodstream where is can travel to the brain to affect the presynaptic neurons there. Clonidine reachs it's max concentration after 60-90 minutes after oral ingestion and has varying bioavailability from 55-87%. Less than 50% of clonidine is metabolized to 4-hydroxyclonidine and excreted in urine, with 50% of the dose being excreted unchanged typically. Alcohol consumption with clonidine should be avoided but food consumption is fine as it does not alter absorption. Overdose of clonidine can lead to hypotension, bradycardia, hypothermia and/or weakness.

Clonidine Mechanism of Pathway References