Description

Tamsulosin hydrochloride is a medication belonging to the class of drugs known as alpha-1 adrenergic receptor antagonists. The Sustained-Release (SR) pellets formulation is designed to release the active drug slowly and consistently over a 24-hour period, allowing for convenient once-daily dosing. Tamsulosin is distinguished from older alpha-blockers by its high selectivity for the alpha-1A and alpha-1D subtypes of the receptor, which are predominantly found in the lower urinary tract.

Indication

Tamsulosin HCl SR pellets are indicated for the treatment of the signs and symptoms of benign prostatic hyperplasia (BPH). BPH is a non-cancerous enlargement of the prostate gland that can cause bothersome urinary symptoms. Tamsulosin helps to improve these symptoms, which include:

• Weak urinary stream
• Urinary urgency
• Hesitancy
• Incomplete bladder emptying

• Nocturia (frequent nighttime urination)

Tamsulosin treats the dynamic component of BPH symptoms by relaxing the smooth muscles of the urinary tract and does not reduce the size of the enlarged prostate itself.

Mechanism of Action

The mechanism of action of Tamsulosin is based on its selective antagonism of alpha-1 adrenergic receptors, which are responsible for smooth muscle contraction in the prostate and bladder neck.

1. Selective Alpha-1A and Alpha-1D Receptor Antagonism: Tamsulosin has a high affinity for alpha-1A and alpha-1D adrenergic receptors. These receptors are the primary subtype found in the smooth muscles of the prostate, bladder neck, and prostatic urethra. By selectively blocking these receptors, tamsulosin minimizes its effect on other alpha-1 receptors, such as the alpha-1B subtype found in blood vessels, which helps to reduce the risk of orthostatic hypotension (a drop in blood pressure upon standing).
2. Smooth Muscle Relaxation: The activation of alpha-1 adrenergic receptors normally leads to the contraction of the smooth muscles of the prostate and bladder neck. This contraction increases the resistance to urine flow, leading to the obstructive and irritative symptoms of BPH. By acting as an antagonist, tamsulosin binds to these receptors and prevents the naturally occurring neurotransmitter, norepinephrine, from binding to them.

3. Improved Urine Flow: The blockade of these receptors results in the relaxation of the smooth muscles in the prostate and bladder neck. This relaxation reduces the dynamic obstruction to urine outflow, leading to an increase in urinary flow rate, a decrease in the feeling of incomplete bladder emptying, and an improvement in the overall symptoms of BPH.