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Alpha Blocker: General Side Effects and Contraindications

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The adrenergic receptors transmit the effects of the sympathetic nervous system and, thus of adrenaline and noradrenaline. The different α1, α2, β1, β2 and β3 receptors mediate entirely different effects depending on the organ. Alpha blockers used in urology are antagonists at the α1 receptor. Review Literatur: (Chapple, 2004).

Alpha Blocker: Pharmacology and Side Effects

Postsynaptic α₁ blocking leads to:

• Smooth muscle relaxation of the prostate, bladder neck, and urethra. Alpha blockers are drugs of the first choice to improve micturition in patients with benign prostatic hyperplasia (BPH).
• Smooth muscle relaxation of the bladder trigonum and distal ureters. Off-label treatment with alpha blocker leads to a faster spontaneous passage of distal ureteral stones.
• The following sub-types of α₁-receptors are known: A, B, D, and L. Type α_1A appears most important in the prostate for inhibiting subvesical obstruction.
• Additional improvement of LUTS by the blockade of α₁-receptors on the spinal level, the urinary bladder, and afferent nerves.
• Arterial and venous vasodilation with reduction of arterial blood pressure. Alpha blockers are drugs of the second choice to treat arterial hypertension.

Indications of Alpha Blocker

• Treatment of benign prostatic hyperplasia: Alpha blockers improve urinary flow and bladder emptying, relieve irritative and obstructive urinary symptoms (LUTS), reduce the risk of urinary retention, improve the success of a trial without a catheter after urinary retention, and are approved for long-term use.
• Off-label treatment of female LUTS due to neurogenic bladder neck obstruction.
• Off-label treatment to improve spontaneous passage of distal ureteral stones.

Side Effects of Alpha Blocker

• The overall rate of side effects is 10–30%; selective alpha_1A-blocker have a reduced cardiovascular side effect rate.
• Initial hypotension, orthostatic collapse, reflex tachycardia, usually transient.
• Increased risk (HR 1,2) of cardiac failure in patients with cardial comorbidity (Lusty et al., 2021).
• Stuffy nose
• Retrograde ejaculation
• Dizziness, weakness.
• Rare side effects: priapism (alpha blocker inhibit sympathetic mechanisms for detumescence), intraoperative floppy iris syndrome during cataract surgery.

Contraindications of Alpha Blocker

Urological Contraindications:

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

Cardiac Contraindications:

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

Other contraindications:

Severe liver insufficiency. Pause alpha blockers before cataract surgery to prevent an intraoperative floppy iris syndrome.

Drug interactions

• Increased hypotensive effect with other antihypertensives or phosphodiesterase-5 inhibitors.
• CYP3A4 inhibitors such as ketoconazole increase the plasma level and side effects.
• Do not combine two alpha blockers for better treatment effect.

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

C. de Mey, “alpha(1)-blockers for BPH: are there differences?,” Eur Urol, vol. 36 Suppl 3, pp. 52–63, 1999.

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