Tamsulosin

Tamsulosin belongs to the group of alpha1-receptor antagonists. It is a methoxy-benzenesulfonamide with the molecular formula _C20H28N2O5S, a molar mass of 408.51 ^g-mol-1 (for tamsulosin; tamsulosin hydrochloride: 444.97 ^g-mol-1) and an average half-life of approx. 12 hours.

Alpha1 receptor antagonists are effective when the corresponding receptor is tonically activated. This is actually the case for the alpha1 receptors of the resistance vessels. This is why they act as antihypertensives. Tamsulosin binds specifically to postsynaptic alpha1 receptors, in particular to the _α1A and _α1D subtypes. This leads to the blockade of these receptors, resulting in a relaxation of the smooth muscles of the bladder neck and the periurethral muscles of the prostate and thus to an improvement in urine flow. Obstructive symptoms are alleviated.

When taken orally, about 57% of tamsulosin is rapidly absorbed from the intestine. Its plasma protein binding is around 99 % and the volume of distribution is low at 0.2 l/kg; tamsulosin therefore only has a low first-pass effect. It is metabolized slowly via the liver. Most of it is present in the plasma in the form of the unchanged active substance. CYP3A4 and also CPY2D6 are involved in the metabolization of tamsulosin. Their inhibition can lead to an increased exposure of tamsulosin. Tamsulosin and its metabolites are mainly excreted in the urine.

Treatment of lower urinary tract symptoms (LUTS) in benign prostatic hyperplasia. The use in women suffering from urinary retention - associated with constriction of the bladder and urethra - (lower urinary tract symptoms, LUTS) is off-label (Zhang HL et al. 2017). Comment: The active substance has only a minor effect on blood pressure. Tamsulosin is not suitable for children with neurogenic voiding dysfunction.

Nephrolithiasis: Drug expulsive therapy (MET) with alpha blockers and calcium channel blockers can increase the rate of excretion and accelerate the elimination of stones. Dosage recommendation: e.g. tamsulosin 1 x 0.4 mg / d (Truß 2005) or nifedipine 40 mg - 60 mg / d.

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

Dizziness, ejaculation disorders including retrograde ejaculation and reduced or absent ejaculation are common. Occasionally headache, orthostatic hypotension, rhinitis (swelling of the nasal mucosa), constipation, diarrhea, nausea, vomiting, exanthema, pruritus, urticaria and angioedema occur. Very rarely, Stevens-Johnson syndrome, priapism, visual disturbances, epistaxis, dry mouth, erythema multiforme and exfoliative dermatitis occur.

The occurrence of so-called "intraoperative floppy iris syndrome" (IFIS) during cataract and glaucoma surgery has been reported in connection with tamsulosin therapy.

In a bivariate analysis of patients with benign prostatic hyperplasia, a correlation between the eruptive occurrence of cherry angiomas(senile angiomas) and the application of tamsulosin was demonstrated. Tamsulosin can therefore be regarded as a possible risk factor for the development of cherry angiomas. Clopidogrel , on the other hand, appears to play a protective role (Nazer RI et al. 2020).Versch. Investigators found a significant correlation between the occurrence of melanoma and eruptive cherry angiomas in younger patients (≤50 years). This correlation could no longer be determined in older patients (Corazza M et al. 2019).

The concomitant use of cimetidine leads to an increase in the plasma level of tamsulosin, whereas furosemide leads to a decrease in the plasma level. A dose adjustment is not necessary as the levels remain within the normal range. Concomitant 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. The concomitant administration of other alpha-1 receptor blockers may result in a marked decrease in blood pressure.

Tamsulosin must not be used for:

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

1. Nazer RI et al (2020) Cherry angioma: A case-control study. J Family Community Med 27:109-113.

2. Kuhlmann U et al. (2015) Nephrology: pathophysiology - clinic - renal replacement procedures. Thieme Verlag 566 - 600

3. Meltzer AC et al (2018) Effect of tamsulosin on passage of symptomatic ureteral stones: A Randomized Clinical Trial. Version 2. JAMA Intern Med 178:1051-1057.

4. 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.

5. 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.