Alpha-adrenergic competitors
Sympathetic nervous system plays an important role in the function of the lower urinary tract by noradrenaline, adrenergic receptors and adrenaline.
Adrenergic receptors (AR) are classified into a-a and b-AR are classified in a1-and a2-adrenergic receptors. The alpha1-adrenergic receptors (a1-AR) are classified into 3 categories and classified according to A1a-AR, a1b a1d-AR and-AR.
Prostate, excel-A1a and a1b-ARs. The A1a-AR constitute 60-85% of a1-Ars in the gland and shown that the percentage increase in hyperplastic tissue. a1-AR are found in abundance than the prostate, bladder and bladder triangle but also in other organs such as the spinal cord, blood vessels, liver and central nervous system.
This distribution justifies the adverse reactions may occur after administration of alpha-adrenergic blockers.
Due to the high concentration of a1-AR in the prostate and bladder neck, use of alpha-adrenergic blockers (a-blockers) seems logical addition and promising for the treatment of LUTS through relaxation of smooth muscle which can to bring.
Phenoxybenzamine, a nonselective alpha-antagonist, was the first a-blocker described and who seemed to have a selective action on the lower urinary tract. Despite the initial enthusiasm was soon abandoned because of the many serious side effects caused.
Prazosin consists early a1-blockers and with other alpha1-adrenergic blockers used for the treatment of BPH. The drawbacks of these substances was that because of the short half-life that had had to be given twice daily.
Terazosin (Hytrin) has been studied more than most, in large multicenter double-blind randomized studies which investigated both the action and the safety of doses 2, 5 and 10mg, with very good results.
Another inhibitor that has been widely studied is doxazosin. Doxazosis unlike terazosin has a longer half-life which allows us to be administered once a day.
The most potent inhibitor alpha1-adrenoceptor is tamsulosin, which exhibits selectivity in A1a-AR. The drug offers improvement in symptoms of men with BPH and can be administered at doses 0,4 mg/24h without showing any serious side effects.
Another alpha adrenergic blocker used to treat BPH is alfuzosin.
When administered formulations of this category should always keep in mind the fact that patients with BPH are usually older with attendant problems, such as hypertension, diabetes and coronary artery disease, for which it is likely to take medication . Thus, administration of alpha-blockers should in most cases be done in conjunction with other drugs the patient is taking and for this reason it is appropriate to calculate the possible side effects of the synergistic action of these.
In conclusion, alpha-blockers are drugs that can lead to remission of symptoms by 20-50% and increase urine flow by 20-30%. The effect is immediate, an improvement from the first 48 hours and the objective improvement requires at least one month treatment, and if after receiving eight weeks have brought about improvement, recommended discontinuation.
