What are the short and longterm side effects of taking Tamsulosin?

I was on Tamsulosin for 10 years (2014-2023); the thought came to me that if Tamsulosin (0.4 mg capsule) relaxed muscles in my prostate and bladder, then it might also result in other “non-urinary-related” effects elsewhere in my body. So, I did some digging……

One side-effect that never occurred to me was that Tamsulosin (an alpha-blocker, used to treat urinary issues such as BPH), can result in deterioration of sleep quality (obstructive events, apneic episodes, and sleep-disordered breathing) due to the relaxing of muscles in the throat and airway.
> Moran 2016: “Reversible Exacerbation of Obstructive Sleep Apnea by Tamsulosin,” Respir Med Case Rep. 2016 Oct 14;19:181–186.

If you search further, you’ll find other possible side-effects of alpha‑blockers, due to their action on alpha‑1 adrenergic receptors, leading to vasodilation and smooth muscle relaxation: low blood pressure, dizziness, headaches, fatigue, and abnormal or retrograde ejaculation, and more.

@brianjarvis Funny that this has come up, Brian. I need cataract surgery and my oldest friend is a retired eye surgeon; so I called him yesterday and peppered him with questions.
He then asked me some, including ‘do you take anything for urination’? It seems that not only do all these muscles you mentioned react to these drugs, the IRIS in the eye is very affected by them as well.
He said that sometimes the cataract surgeries become impossible because the iris just flops around and makes lens implantation extremely difficult.
Luckily, I am not using any of these.
Phil

If you were going to experience side effects most should have been seen in the last 5 years except for the floppy Iris (usually need to discontinue 30 days before cataract surgery). It increased my heart rate enough that I stopped taking it. It also made me dizzy. Can affect any smooth muscle.

@heavyphil (A lengthy response……) Shortly after starting Tamsulosin (Flomax) in 2014, I became aware that my sleep quality had worsened. Having no knowledge of the adverse side-effects of these prescribed medications (other than what we all knew were genitourinary-related), I only knew that I was not sleeping normally (nor sleeping well). So, I began to look into the effects on sleep of these pharmaceuticals that I was taking as part of my prostate cancer therapies.

In addition to the side-effects of Tamsulosin that I mentioned earlier, I was on Finasteride (started in 2016), and much later Casodex (Bicalutamide), and Eligard (Leuprolide Acetate).

What I found —>
Finasteride (a 5-alpha-reductase inhibitor), is associated with sleep disturbances, including insomnia and fatigue. Sleep disturbances are among the widely reported symptoms of Post-Finasteride Syndrome in patients who struggle with persistent side effects even after stopping the medication.
> Clio 2025: Post-finasteride syndrome - a true clinical entity,” Your Sexual Medicine Journal; Springer Nature Limited; 14 February 2025.
> Gupta 2018: “Finasteride is Associated with a Higher Odds of Obstructive Sleep Apnea (OSA),” Sleep, Volume 41, Issue suppl_1, 27 April 2018, Pages A340–A341.

Casodex (a non-steroidal androgen receptor antagonist that exerts anti-androgenic effects on peripheral tissues), impacts metabolism by blocking testosterone from binding to androgen receptors. Testosterone naturally modulates sleep architecture and energy, operating in a powerful bidirectional cycle with sleep. Blocking testosterone causes central nervous system side effects, including drowsiness, lethargy, and a lack of baseline physical strength.
> Aulakh 2025: “Bicalutamide: A review.” Journal of Cutaneous and Aesthetic Surgery; Volume 18; Issue 2; April-June 2025; pages 78-85.
> Anderson 2026: “Sleep apnea, heart health and testosterone: unravelling the triad of well-being.” The Lancet. Vol 125 March, 2026; 2026;125: 106157.

Eligard (a gonadotropin-releasing hormone agonist), suppresses systemic testosterone to below castrate levels. Testosterone suppression often triggers or contributes to the progression of apneic events, due to related metabolic changes which further worsens airway obstruction. When combined with Casodex, the profound daytime exhaustion reinforces a cycle of metabolic slowdown, causing further relaxation of the neck muscles, narrowing the airway, and worsening nighttime breathing obstructions.
> Mateika 2004: “Treatment with leuprolide acetate decreases the threshold of the ventilatory response to carbon dioxide in healthy males,” J Physiol. 2004 Sep 16; 561(Pt 2): 637–646.
> Saylor 2010: “Adverse Effects of Androgen Deprivation Therapy: Defining the Problem and Promoting Health Among Men with Prostate Cancer,” J Natl Compr Canc Netw.

These are all very toxic pharmaceuticals; they change the way the body naturally functions. So, what seemed to me to be lack of sleep due to my concern regarding my prostate cancer diagnosis and therapies, was instead quite possibly biologic (metabolic, endocrine, and physiologic) impairment due to the pharmaceuticals being used to treat my prostate cancer and residuals.

Again, my focus was only on my sleep quality, not anything else – since sleep can have far-reaching adverse effects on quality of life (due to the physiologic response and disrupted circadian rhythm).

@borshch, I hope you saw the helpful responses to your question about tamsulosin from the guys. Here are a few related discussions that may also interest you:

- Tips for getting off Flomax (tamsulosin)? https://connect.mayoclinic.org/discussion/tips-for-getting-off-flomax-tamsulosin/

See all in groups search results: https://connect.mayoclinic.org/group/prostate-cancer/

Have you noticed any side effects? Are you considering whether you should continue with tamsulosin or not?

@brianjarvis I have been on tamsulosin since Feb this year. The tiredness and dizzy feeling were quite apparent earlier on, with some lessening after 3 months. However the effects have not totally abated. There are other side effects but it does what it is supposed to do. I was getting up 5 or more times a night that has lessened to 1 or 2 times a night. Have to stay away from coffee.

@grandmira It’s known that Tamsulosin also lowers blood pressure - which may help explain your “… tiredness and dizzy feeling.” Excess Tamsulosin can even cause vertigo,

Years ago it was noticed that guys who were given blood pressure medication also peed better.