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Alpha-Blocker (2/5): Doxazosin

• Alpha-blocker (1/6): General pharmacology
• Alpha-blocker (2/6): Terazosin
• Alpha-blocker (3/6): Doxazosin
• Alpha-blocker (4/6): Tamsulosin
• Alpha-blocker (5/6): Alfuzosin
• Alpha-blocker (6/6): Silodosin

Review Literatur: (Chapple, 2004).

General Pharmacology of Doxazosin

Please see section general pharmacology of alpha-blocker.

Mechanism of Action of Doxazosin

Doxazosin is a non-selective alpha₁-blocker with a long elimination half-life.

Indications for Doxazosin

• Treatment of lower urinary tract symptoms due to benign prostatic hyperplasia
• Treatment of arterial hypertension

Pharmacokinetics of Doxazosin

• Elimination half-life 22 h

Doxazosin: Mechanism of Action

Postsynaptic alpha₁-blockade leads to:

• Arterial and venous vasodilation, hypotension
• Smooth muscle relaxation of the prostate, bladder neck and the urethra. Alpha-blocker improve the dynamic component of subvesical obstruction due to benign prostatic hyperplasia (BPH).
• Positive effect on the lipid metabolism by lowering cholesterol and triglycerides

Side Effects of Doxazosin

• Hypotension, orthostatic syncope, reflex tachycardia
• Stuffy nose
• Retrograde ejaculation
• Tachyphylaxis in the treatment of hypertension due to volume retention and peripheral edema.
• Dizziness, weakness
• Overall rate of side effects is between 10–30%

Contraindications of Doxazosin

Urological Contraindications:

Conservative treatment of BPH is not indicated, if surgical treatment is imperative: chronic urinary retention with renal failure, recurrent hematuria due to prostatic enlargement, recurrent infections and bladder stones.

Cardiac Contraindications:

Hypotension, mechanical heart failure (valvular, pulmonary embolism, pericarditis), congestive heart failure.

Other contraindications:

Doxazosin should be paused perioperatively for cataract surgery to prevent an intraoperative floppy iris syndrome.

Dosage of Doxazosin

The treatment of doxazosin should be started with a low dosage, such as 1 mg 1-0-0. The dosage can be increased each week to 2–4–8 mg 1-0-0, depending on treatment effect, side effects and blood pressure.

References

Chapple 2004 CHAPPLE, C. R.:

Pharmacological therapy of benign prostatic hyperplasia/lower urinary tract symptoms: an overview for the practising clinician.
In: BJU Int
94 (2004), Nr. 5, S. 738–44

  Deutsche Version: Doxazosin