Tamsulosin

Author: Prof. Dr. med. Peter Altmeyer

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Last updated on: 29.10.2020

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Synonym(s)

CAS-Nummer:106133-20-4; (R)-(-)-5-{2-[2-(2-ethoxyphenoxy)-ethylamino]propyl}-2-methoxy-benzenesulfonamide

Definition
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Tamsulosin belongs to the group of alpha1 receptor antagonists. It is a methoxy-benzenesulfonamide with the molecular formula: C20H28N2O5S, a molar mass of 408.56 g-mol-1 and an average half-life of about 12.0 H.

Spectrum of action
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Alpha1 receptor antagonists are effective when the corresponding receptor is tonic activated. However, this is the case for the alpha1 receptors of the resistance vessels. This is why they act as antihypertensives. Tamsulosin binds specifically to postsynaptic alpha1 receptors, especially to the subtypes alpha1A and alpha1D. This leads to a blockage of these receptors, to a relaxation of the muscle tone in the bladder neck, the smooth muscles of the prostate and thus to an improvement of the urine flow. Obstructive symptoms are relieved.

When taken orally, tamsulosin is rapidly absorbed from the bowel at about 57% of the applied dose. Tamsulosin is bound to plasma proteins to about 99% and the distribution volume is low at 0.2 l/kg. Thus, tamsulosin has only a low first-pass effect. It is slowly metabolised via the liver. Most of it is present in plasma in the form of the unchanged active substance. CYP3A4 and also CPY2D6 are involved in the metabolism of tamsulosin. Their inhibition can lead to an increased exposure of tamsulosin. Tamsulosin and its metabolites are mainly excreted in the urine.

Indication
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Treatment of symptoms of the lower urinary tract (LUTS) in benign prostatic hyperplasia. The application in women who suffer from urinary retention associated with narrowing of the bladder and urethra (lower urinary tract symptoms LUTS), the use is an off-label use (Zhang HL et al 2017). Note: The drug has only a minor effect on blood pressure. Tamsulosin is not suitable for children with neurogenic voiding disorders.

Nephrolithiasis: Drug expulsive therapy (MET) with alpha blockers and calcium channel blockers can increase the rate of excretion and speed up the rate of stone loss. Dosage recommendation: e.g. Tamsulosin 1 x 0,4 mg / d (Truß 2005) or Nifedipin 40 mg - 60 mg / d.

Dosage and method of use
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The dosage is 0.4 mg tamsulosin-HCl once daily. Tamsulosin is taken orally. It can be taken independently of meals.

Undesirable effects
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Frequent are dizziness, ejaculation disorders including retrograde ejaculation, and reduced or no ejaculation. Occasionally, headaches, orthostatic hypotension, rhinitis (swelling of the nasal mucosa), constipation, diarrhea, nausea, vomiting, exanthema, pruritus, urticaria and angioedema are reported. Very rare: 'Stevens-Johnson syndrome, priapism, visual disturbances, epistaxis, dry mouth, erythema multiforme, exfoliative dermatitis.

In connection with tamsulosin therapy, the occurrence of intraoperative floppy iris syndrome (IFIS) during cataract and glaucoma surgery has been reported.

Interactions
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Simultaneous use of cimetidine leads to an increase in plasma levels of tamsulosin, whereas furosemide leads to a decrease in plasma levels. A dose adjustment is not necessary as the levels remain in the normal range. Simultaneous use with strong (e.g. ketoconazole) and moderate (e.g. erythromycin) CYP3A4 inhibitors may lead to increased exposure to tamsulosin and should be used with caution. Diclofenac and warfarin may increase the elimination rate of tamsulosin. Simultaneous administration of other alpha-1 receptor blockers could lead to strong antihypertensive effects.

Contraindication
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Tamsulosin must not be used for:

hypersensitivity to the active substance, including drug-induced angioedema, known orthostatic hypotension, severe liver failure.

Literature
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  1. Kuhlmann U et al (2015) Nephrology: Pathophysiology - Clinic - Kidney replacement procedure. Thieme Publishing House 566 - 600

  2. Meltzer AC et al (2018) Effect of Tamsulosin on Passage of Symptomatic Ureteral Stones: A Randomized Clinical Trial. JAMA Internal Med 178:1051-1057.

  3. Wang RC et al (2017) Effect of Tamsulosin on Stone Passage for 11Ureteral Stones: A Systematic Review and Meta-analysis. Annals of Emergency Medicine 69:353-361.

  4. Zhang HL et al (2017) Tamsulosin for treatment of lower urinary tract symptoms in women: a systematic review and meta-analysis. Int J Impot Res 29:148-156.

Outgoing links (1)

Nephrolithiasis;

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Last updated on: 29.10.2020