Doxazosin

Q: What systemic side effects, besides orthostatic hypotension, does doxazosin cause?

Reflex tachycardia — a moderate increase in heart rate in response to vasodilation.Peripheral edema — can occur during therapy.Frequency of urination — associated with decreased smooth muscle tone of the bladder neck and urethra sphincters.Nasal congestion — caused by vasodilation of the nasal mucosa blood vessels.

Q: Through what pathways and in what form is doxazosin eliminated from the body?

Metabolite excretion — the drug is extensively metabolized in the liver, after which its metabolites are excreted primarily via the gastrointestinal tract.

*Doxazosinum*

For medical students2 min readUpdated 2026-10-10

Doxazosin is a selective competitive postsynaptic $\alpha_1$-adrenergic receptor blocker used in cardiology and urology. The drug provides a smooth reduction in blood pressure and eases urination in benign prostatic hyperplasia.

Trade namesCardura, Artezin, Kamiren, Tonocardin

SelectivityAffinity for $\alpha_1$ is 600 times higher than for $\alpha_2$

Half-life19–22 hours (administered once daily)

Bioavailability60–70% upon oral administration

Pharmacodynamics and Mechanism of Action

The drug selectively and competitively blocks postsynaptic $\alpha_1$-adrenergic receptors. Its affinity for this receptor subtype exceeds that of the $\alpha_2$-subtype by 600-fold. In urological practice, the therapeutic effect is achieved by blocking $\alpha_{1A}$-adrenergic receptors, which are localized in the muscular stroma, prostate capsule, and bladder neck, leading to tissue relaxation and improved urine outflow.

Pharmacokinetics and Dosing Regimen

The substance exhibits good systemic absorption in the gastrointestinal tract (80–90%). Due to intensive first-pass hepatic metabolism, the resulting bioavailability is 60–70%.

Peak concentration ($C_{max}$): peaks at 3 hours with morning administration, and 5 hours with evening administration. Food intake delays absorption by 1 hour.
Elimination: metabolites leave the body primarily via the intestines.
Half-life ($T_{1/2}$): ranges from 19 to 22 hours, allowing once-daily dosing.

Clinical Effects and Combination Therapy

The antihypertensive effect develops gradually, avoiding sharp blood pressure spikes. The maximum effect is observed 2–6 hours after administration, and the overall duration persists throughout the 24-hour period.

Application options:

Monotherapy for arterial hypertension.
Combination regimens with thiazide diuretics, $\beta$-blockers, calcium channel blockers, and ACE inhibitors.
Treatment of benign prostatic hyperplasia (BPH).

Pleiotropic Properties and Safety Profile

In addition to its primary action, the drug has a positive impact on metabolism and the hemostatic system:

Reduces platelet aggregation and increases active tissue plasminogen activator levels.
Exhibits metabolic benefits regarding the lipid profile: decreases total cholesterol and triglycerides while increasing high-density lipoproteins (HDL).

Safety: the drug is generally well tolerated. The main specific adverse effect is postural (orthostatic) hypotension, which is most pronounced at the very beginning of pharmacotherapy.

Mnemonic

Dox-AZO-sin — Alpha-1 zonal blocker: relaxes blood vessels and bladder neck for a full day ($T_{1/2}$ up to 22 hours), taken once a day.

Frequently asked questions

What systemic side effects, besides orthostatic hypotension, does doxazosin cause?

Reflex tachycardia — a moderate increase in heart rate in response to vasodilation.
Peripheral edema — can occur during therapy.
Frequency of urination — associated with decreased smooth muscle tone of the bladder neck and urethra sphincters.
Nasal congestion — caused by vasodilation of the nasal mucosa blood vessels.

Through what pathways and in what form is doxazosin eliminated from the body?

Metabolite excretion — the drug is extensively metabolized in the liver, after which its metabolites are excreted primarily via the gastrointestinal tract.

What is the dosing frequency and what determines it?

The drug is taken once daily. This is due to its pharmacokinetic properties, specifically the long half-life ($T_{1/2}$), which is 19–22 hours.

What is the primary side effect characteristic of treatment initiation?

The main adverse effect is postural (orthostatic) hypotension, which is most commonly observed during the first days of starting the course.

How does doxazosin affect a patient's lipid profile?

The drug demonstrates metabolic neutrality and benefit: it lowers total cholesterol and triglycerides, and increases the concentration of high-density lipoproteins (HDL).

Go deeper

Comparative characteristics of selective and non-selective $\alpha$-adrenergic blockers
First-pass hepatic metabolism features for quinazoline derivatives
Pathogenetic mechanisms of orthostatic hypotension during $\alpha_1$-receptor blockade
The role of $\alpha_{1A}$-receptor blockade in lower urinary tract urodynamics
Metabolic aspects of combination antihypertensive therapy