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Alpha Blocker: General Side Effects and Contraindications

• Alpha blockers: General pharmacology
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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.
• Following sub-types of α₁-receptors are known: A, B, D, and L. Type α_1A appears to be most important in the prostate for the inhibition of subvesical obstruction.
• Additional improvement of LUTS by the blockade of α₁-receptors on the spinal level, in the urinary bladder, and on 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 lower urinary tract symptoms due to benign prostatic hyperplasia.
• 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

• Overall rate of side effects is between 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.

Contraindications of Alpha Blocker

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 urinary tract infections or bladder stones.

Cardiac Contraindications:

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

Other contraindications:

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

Drug interactions

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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