Pharmacodynamics
Blocker of α1-adrenergic receptors; agent for the symptomatic treatment of benign prostatic hyperplasia.
Selectively blocks postsynaptic α1A-adrenergic receptors of smooth muscles of the prostate gland, bladder neck, prostatic urethra. As a result, the tone of the smooth muscles of these formations decreases, the outflow of urine is facilitated. At the same time, the symptoms of obstruction and irritation associated with benign prostatic hyperplasia are reduced. The therapeutic effect appears after about 2 weeks from the start of treatment.
In tamsulosin, the ability to block α1B-adrenergic receptors of vascular smooth muscle is significantly less pronounced, therefore, the effect on systemic blood pressure is negligible.
Pharmacokinetics
After oral administration, tamsulosin is rapidly and almost completely absorbed from the digestive tract. After a single oral administration of 400 μg Cmax of active substance in plasma is achieved after 6 hours.
Binding to plasma proteins - 99%. Vd is negligible and amounts to 0.2 l / kg.
Tamsulosin is slowly metabolized in the liver with the formation of pharmacologically active metabolites that maintain high selectivity for α1A-adrenergic receptors. Most of the active substance is present in the blood unchanged.
T1 / 2 of tamsulosin with a single dose is 10 hours, the terminal T1 / 2 is 22 hours. It is excreted by the kidneys, 9% - unchanged.
Contraindications
Hypersensitivity to tamsulosin.
Side effects
From the cardiovascular system: rarely - dizziness, orthostatic hypotension, palpitations.
From the side of the central nervous system: headache, asthenia are possible.
From the reproductive system: rarely - retrograde ejaculation.
Interaction
With the simultaneous use of tamsulosin with cimetidine, there was a slight increase in the concentration of tamsulosin in the blood plasma, and with furosemide, a decrease in the concentration; with other α1-blockers - a pronounced increase in the hypotensive effect is possible.
Diclofenac and indirect anticoagulants slightly increase the rate of elimination of tamsulosin.
Diazepam, propranolol, trichloromethiazide, chlormadinone, amitriptyline, diclofenac, glibenclamide, simvastatin and warfarin do not change the free tamsulosin fraction in human plasma in vitro. In turn, tamsulosin also does not alter the free fractions of diazepam, propranolol, trichloromethiazide and chlormadinone.
In in vitro studies, no interaction was found at the level of hepatic metabolism with amitriptyline, salbutamol, glibenclamide and finasteride.
Other α1-blockers, acetylcholinesterase inhibitors, alprostadil, anesthetics, diuretics, levodopa, antidepressants, beta-blockers, slow calcium channel blockers, muscle relaxants, nitrates and ethanol can increase the severity of the hypotensive effect.
Dosage and administration
Inside - 400 mcg 1 time / day (after breakfast).
Special instructions
It is used with caution in patients prone to arterial hypotension, with severe impaired liver function.
Before starting tamsulosin therapy, the patient should be examined for other diseases that can cause the same symptoms as benign prostatic hyperplasia. Before starting treatment and regularly during therapy, a digital rectal examination should be performed and, if required, the determination of a specific antigen of the prostate. In patients with impaired renal function, a change in the dosage regimen is not required.
Influence on the ability to drive vehicles and control mechanisms
During the treatment period, it is necessary to refrain from engaging in potentially hazardous activities that require an increased concentration of attention and speed of psychomotor reactions.
