Drug Groups

approved

Description

Doxazosin is a quinazoline-derivative that selectively antagonizes postsynaptic α₁-adrenergic receptors. It may be used to mild to moderate hypertension and in the management of symptomatic benign prostatic hyperplasia (BPH). α₁-Receptors mediate contraction and hypertrophic growth of smooth muscle cells. Antagonism of these receptors leads to smooth muscle relaxation in the peripheral vasculature and prostate gland.

Indication

For treatment and management of mild to moderate hypertension and urinary obstruction symptoms caused by BPH.

Pharmacology

Doxazosin is an alpha-adrenergic blocking agent used to treat hypertension and benign prostatic hyperplasia. Accordingly, Doxazosin is a selective inhibitor of the alpha1 subtype of alpha adrenergic receptors. In the human prostate, Doxazosin antagonizes phenylephrine (alpha1 agonist)-induced contractions, in vitro, and binds with high affinity to the alpha1c adrenoceptor, which is thought to be the predominant functional type in the prostate. Studies in normal human subjects have shown that Doxazosin competitively antagonized the pressor effects of phenylephrine (an alpha1 agonist) and the systolic pressor effect of norepinephrine. The antihypertensive effect of Doxazosin results from a decrease in systemic vascular resistance and the parent compound Doxazosin is primarily responsible for the antihypertensive activity.

Toxicity

Symptoms of overdose include hypotension. Oral LD₅₀ is greater than 1000 mg/kg in mice and rats.

Affected Organisms

Biotransformation

Hepatic.

Absorption

65%

Half Life

22 hours

Protein Binding

98%

Elimination

On average only 4.8% of the dose was excreted as unchanged drug in the feces and only a trace of the total radioactivity in the urine was attributed to unchanged drug.

References

External Links