| Indication |
For use alone or in combination with other classes of
antihypertensive agents in the management of hypertension. Has also been
used for the treatment of attention deficit hyperactivity disorder
(ADHD) in pediatric patients. |
| Pharmacodynamics |
Guanfacine is a phenylacetyl-guanidine derivative hypotensive
and a centrally-acting, alpha(2)-adrenergic receptor agonist used alone
or in combination with other drugs for the treatment of hypertension. |
| Mechanism of action |
Guanfacine selectively stimulates central alpha(2)-adrenergic
receptors, resulting in inhibition of sympathetic vasomotor centers,
which contributes predominantly to the hypotensive effects of the drug.
Central effects of guanfacine lead to reduced peripheral sympathetic
nerve impulses from the vasomotor center to the heart and blood vessels.
This results in a decrease in peripheral vascular resistance and a
reduction in heart rate. The stimulation of peripheral
alpha(2)-adrenergic receptors may also contribute to hypotensive
effects. |
| Absorption |
Rapid and complete, with an oral bioavailability of approximately 80%. |
| Volume of distribution |
|
| Protein binding |
Approximately 70% bound to plasma proteins, independent of drug concentration. |
| Metabolism |
Hepatic |
| Route of elimination |
In individuals with normal renal function, guanfacine and its metabolites are excreted primarily in the urine. |
| Half life |
17 hours (range 10-30 hours) |
| Clearance |
Not Available |
| Toxicity |
Symptoms of overdose include drowsiness, lethargy, bradycardia and hypotension. LD50=165mg/kg (orally in mice) |
