Alpha Blocker

Products

Alpha blockers are available in many countries in the form of tablets, sustained-release tablets, capsules, and sustained-release capsules. The most commonly prescribed today is tamsulosin (Pradif T, generic). Alpha blocker is short for alpha1-adrenoreceptor antagonist.

Structure and properties

The first alpha blockers-alfuzosin, doxazosin, and terazosin-were developed as derivatives of quinazoline:

Effects

Alpha blockers (ATC G04CA) have sympatholytic, vasodilator, and antihypertensive properties. They dilate blood vessels and lead to a reduction in blood pressure by lowering vascular resistance. Their effects are based on competitive antagonism at alpha1-adrenoceptors. This cancels the effects of the natural ligands norepinephrine and adreanlin. Alpha blockers belong to the group of sympatholytics. Alpha blockers relax the smooth muscles of the prostate and urethra and improve the symptoms of benign prostate enlargement. The alpha1A receptor is mainly found in the prostate and urinary tract. Therefore, alpha blockers have been developed which are selective for this receptor. These include tamsulosin and silodosin. They are thought to cause fewer cardiovascular side effects.

Indications

Alpha blockers are administered for the treatment of symptoms of benign prostatic hyperplasia on the one hand and for the treatment of hypertension on the other. Usually, a drug is approved for only one indication.

Dosage

According to the SmPC. The dosage depends on the product. The medicines which are on the market today are usually taken once a day.

Active ingredients

Benign Prostate Enlargement:

Treatment of hypertension:

Some beta-blockers have an additional alpha-blocking effect carvedilol (Dilatrend) and labetalol (Trandate). In many countries, not or no longer on the market:

  • Bunazosin (D)
  • Phentolamine (Regitin, out of trade).
  • Prazosin (out of trade)
  • Tolazolin (out of trade)

Contraindications

Contraindications include (selection):

  • Hypersensitivity
  • Orthostatic hypotension
  • Concurrent use of other alpha blockers.
  • Hepatic / renal insufficiency (depending on the active substance).

Full precautions can be found in the drug label.

Interactions

Other antihypertensive agents or antihypertensive drugs such as the phosphodiesterase-5 inhibitors may result in increased lowering of blood pressure. These agents are substrates of CYP450 isozymes.

Adverse effects

The most common possible adverse effects include:

  • Orthostatic hypotension
  • Drowsiness, dizziness, headache, drowsiness.
  • Visual disturbances
  • Erectile dysfunction, ejaculatory disorders
  • Gastrointestinal disorders