"Ejaculatory disorders and alpha1-adrenoceptor antagonists therapy: clinical and experimental researches"

Abstract

Background: It is well known that the use of the alpha-adrenergic receptor antagonists in the BPH therapy may induce ejaculatory disorder. A review of clinical literature shows a greater incidence of ejaculatory disorder during the use of tamsulosin compared with alfuzosin. Anejaculation has been until now referred to retrograde ejaculation due to relaxation of prostatic and bladder neck smooth muscle tone. In a recent researches was evaluated the effect of tamsulosin and alfuzosin on rat vas deferent "in vitro", concluding that tamsulosin may "cause ejaculatory dysfunction by altering the progression and emission of sperm". An abnormal increase of contraction would be the cause of ejaculatory disorder. The aim of our paper is to compare human and rat vas deferens contractile activity and to evaluate with a clinical study if tamsulosin causes retrograde ejaculation disorder.

Methods: We have revaluated the human and rat vas deferens contractile activity in vitro according to our experience and literature. We have also performed a clinical study on 10 patients (48-72 y) affected by anejaculation. Post-coital urine was examined to search spermatozoa.

Results: Human and rat vas deferens activity is not comparable. Contractile activity induced by norepinephrin after tamsulosin incubation in rat prostatic vas deferens strips is similar to the contractile activity evoked by norepinephrin in human strips. Spermatozoa were found in post coital urine of 6 patients.

Conclusion: In our opinion the treatment with tamsulosin may induce retrograde ejaculation but not other ejaculatory disorder due to abnormal sperm progression.

Figure 1

Response of an "epididymal" portion of the human vas deferens to a stimulation with noradrenaline (at the dose of 1.10–6 gm/ml). The tonic component prevails over the phasic one.

Figure 2

The typical response of the "prostatic" deferent duct has been characterized by an initial tonic-phasic "mixed" activity, immediately followed by a phasic activity marked by rapid strong "twitch-like" contractions. These latter may suggest the presence of a mechanism recruiting muscle cells, as if the vas deferens has a pace-maker action which is morphologically quite similar to the "twitch" that can be highlighted by electric stimulation.

Figure 3

Following a dose-response stimulation with cumulative logarithmic doses of noradrenaline, it has been possible to observe that high doses of mediator markedly increase the basic tone without altering the maximum contraction (which is manifest in rapid phasic contractions), as if the "twitch" represents a contraction caused by the simultaneous excitation of all muscle cells and cannot be consequently exceeded.