Amso Mechanism of Action

Pharmacotherapeutic Group: α1-adrenoceptor antagonists.
Pharmacology: General: The symptoms associated with benign prostatic hyperplasia (BPH) are related to bladder outlet obstruction, which is comprised of two underlying components: static and dynamic. The static component is related to an increase in prostate size caused, in part, by a proliferation of smooth muscle cells in the prostatic stroma. However, the severity of BPH symptoms and the degree of urethral obstruction do not correlate well with the size of the prostate. Tamsulosin Hydrochloride (Amso), an alpha1 adrenoreceptor blocking agent, exhibits selectivity for alpha1 receptors in the human prostate.
Pharmacodynamics: Mechanism of Action: Tamsulosin (Amso) binds selectively and competitively to the post-synaptic-α1-adrenoceptors, in particular to subtypes α_1A and α_1D. It brings about relaxation of prostatic and urethral smooth muscle.
Pharmacodynamic Effects: Tamsulosin Hydrochloride (Amso) increases the maximum urinary flow rate. It relieves obstruction by relaxing smooth muscle in prostate and urethra thereby improving voiding symptoms.
It also improves the storage symptoms in which bladder instability plays an important role.
These effects on storage and voiding symptoms are maintained during long-term therapy. The need for surgery or catheterization is significantly delayed.
Pharmacokinetics: Absorption: Tamsulosin Hydrochloride (Amso) is a prolonged release capsule of the non-ionic gel matrix type. The OCAS (Oral Controlled Absorption System) formulation provides consistent slow release of Tamsulosin (Amso), resulting in an adequate exposure, with little fluctuation, over 24 hours.
Tamsulosin (Amso) administered is absorbed from the intestine. Under fasting conditions of the administered dose, approximately 57% is estimated to be absorbed.
Tamsulosin (Amso) shows linear pharmacokinetics.
After single dose of Tamsulosin Hydrochloride (Amso) capsule in the fasted state, plasma concentrations of Tamsulosin peak at a median time of 6 hours. In steady state, which is reached by day 4 of multiple dosing, plasma concentrations of Tamsulosin (Amso) peak at 4 to 6 hours, in the fasted and fed state. Peak plasma concentrations increase from approximately 6 mg/mL after the first dose to 11 mg/mL in steady state.
As a result of the prolonged release characteristics of Tamsulosin Hydrochloride (Amso) capsule the trough concentration of Tamsulosin in plasma amounts to 40% of the peak plasma concentration under fasted and fed condition.
There is a considerable inter-patient variation in plasma levels both after single and multiple dosing.
Distribution: In man, Tamsulosin (Amso) is about 99% bound to plasma proteins. The volume of distribution is small (about 0.2 L/Kg).
Metabolism: Tamsulosin (Amso) has a low first pass effect, being metabolized slowly. Most Tamsulosin (Amso) is present in plasma in the form of unchanged active substance. It is metabolized in the liver.
Excretion: Tamsulosin (Amso) and its metabolites are mainly excreted in the urine.