Why does tamsulosin (alpha-1 adrenergic receptor blocker) interfere with ejaculation?

From the Guidelines

Tamsulosin interferes with ejaculation because it blocks alpha-1 adrenergic receptors in the smooth muscles of the prostate, bladder neck, and vas deferens, leading to retrograde ejaculation or reduced ejaculate volume in approximately 8-18% of men taking the standard dose of 0.4 mg daily. This blockade relaxes these muscles, which normally contract during ejaculation to propel semen forward. When these muscles are relaxed due to tamsulosin, the semen cannot be properly expelled through the urethra, resulting in ejaculatory dysfunction. The effect is dose-dependent and usually reversible when the medication is discontinued 1. Tamsulosin has higher selectivity for alpha-1A receptors, which are predominant in the prostate and male reproductive tract, explaining why it affects ejaculation more frequently than some other medications in the same class.

Key Points to Consider

• The choice of alpha blocker, such as tamsulosin, should be based on patient age and comorbidities, and different adverse event profiles, including ejaculatory dysfunction (EjD) and changes in blood pressure 1.
• Patients should be informed about the potential side effect of ejaculatory dysfunction before starting tamsulosin therapy, especially if fertility is a concern, though the medication does not typically affect sexual desire or erectile function.
• The American Urological Association recommends offering one of the following alpha blockers as a treatment option for patients with bothersome, moderate to severe LUTS/BPH: alfuzosin, doxazosin, silodosin, tamsulosin, or terazosin, with the choice based on individual patient factors 1.

Clinical Implications

• Clinicians should discuss the potential risks and benefits of tamsulosin with patients, particularly those with concerns about fertility or sexual function.
• The medication's efficacy in relieving symptoms of benign prostatic hyperplasia (BPH) should be weighed against the potential for ejaculatory dysfunction and other adverse effects.
• Regular monitoring and follow-up are essential to assess the patient's response to treatment and adjust the medication regimen as needed to minimize adverse effects while maximizing therapeutic benefits 1.

From the FDA Drug Label

Abnormal Ejaculation Abnormal ejaculation includes ejaculation failure, ejaculation disorder, retrograde ejaculation, and ejaculation decrease. As shown in Table 1, abnormal ejaculation was associated with Tamsulosin Hydrochloride Capsules administration and was dose-related in the U. S. studies.

Tamsulosin interferes with ejaculation because abnormal ejaculation is a known side effect associated with its administration, and it is dose-related. The exact mechanism of how tamsulosin affects ejaculation is not explicitly stated in the label, but it is acknowledged as a potential issue, with abnormal ejaculation including conditions such as ejaculation failure, ejaculation disorder, retrograde ejaculation, and ejaculation decrease 2.

From the Research

Tamsulosin and Ejaculation Interference

• Tamsulosin, an alpha-1 adrenergic receptor blocker, has been found to interfere with ejaculation in several studies 3, 4, 5, 6, 7.
• The exact mechanism of this interference is not fully understood, but it is thought to be related to the relaxation of prostatic and bladder neck smooth muscle tone, as well as an abnormal increase in contraction of the vas deferens 3.
• Studies have shown that tamsulosin can cause a decrease in ejaculate volume and an increase in the incidence of anejaculation (complete lack of ejaculation) compared to other alpha-1 adrenergic receptor blockers such as alfuzosin 5, 7.
• The incidence of ejaculatory dysfunction with tamsulosin has been reported to be around 10% in some studies, which is higher than with other alpha-1 adrenergic receptor blockers 5.
• Tamsulosin has also been found to have a negative effect on sperm parameters in healthy men, including a decrease in sperm concentration and motility 6.

Possible Mechanisms

• The mechanism of tamsulosin's effect on ejaculation is thought to be related to its action on the alpha-1 adrenergic receptors in the smooth muscle of the prostate and bladder neck 3.
• Tamsulosin may also have a peripheral effect on the seminal vesicles and/or the vas deferens, which could contribute to its effect on ejaculation 5.
• A central effect of tamsulosin on the brain's control of ejaculation is also possible, as it has been shown to have a strong affinity for 5HT1A- and D2-like receptors, which are involved in the central command of ejaculation 5.

Clinical Implications

• The interference of tamsulosin with ejaculation is a significant side effect that should be considered when prescribing this medication for the treatment of benign prostatic hyperplasia (BPH) 4, 5.
• Patients should be informed of the potential risk of ejaculatory dysfunction with tamsulosin and monitored for any changes in their sexual function during treatment 4.
• Alternative treatments for BPH may be considered for patients who experience significant ejaculatory dysfunction with tamsulosin 5.