Prostate symptoms and sex: what the treatments actually do

Urinary symptoms from an enlarging prostate are treated very effectively in the UK, and the treatments have specific sexual effects that men are frequently not warned about. Not vaguely — specifically. The two main classes of medicine affect completely different parts of sexual function, and knowing which does what changes how you interpret what is happening to you.

The two classes, and what each one does

Alpha blockers: an ejaculation effect, not an erection effect

Alpha blockers — tamsulosin is the usual UK first choice, with alfuzosin the common alternative — relax smooth muscle in the prostate and bladder neck. They work quickly, usually within days to a couple of weeks.

Their characteristic sexual effect is ejaculatory dysfunction: reduced volume of ejaculate, or none at all, with orgasm otherwise preserved. Mechanistically this is largely failure of seminal emission rather than true retrograde ejaculation, though UK guidelines and product information commonly use the “retrograde” label, which is why you will see it described both ways.

It is strongly dose- and drug-dependent. The more prostate-selective agents cause it far more often: reported rates for tamsulosin run roughly 4–18% across trials and for silodosin up to around 28%, against about 1% for alfuzosin ^{[2, 3]}. That difference is clinically useful, because switching within the class is a real option for a man to whom ejaculation matters.

Two things men are often not told:

• It reverses on stopping. This is not a permanent change.
• Alpha blockers do not cause erectile dysfunction, and may slightly improve it as urinary symptoms settle. If erections have deteriorated since starting one, look elsewhere for the cause rather than blaming the tablet.

5-alpha reductase inhibitors: a libido and erection effect

Finasteride and dutasteride shrink the prostate by blocking conversion of testosterone to dihydrotestosterone. They are used where the prostate is enlarged — UK guidance typically requires a prostate above 30 g or a PSA above 1.4 ng/ml with moderate to severe voiding symptoms — and they take three to six months to work ^{[1, 3]}.

This is the class associated with reduced libido, erectile difficulty and ejaculatory problems. Product information puts each broadly in the 3–8% range in the first year, generally declining with continued use, and placebo rates in the same trials are high ^[6]. Gynaecomastia and breast tenderness also occur, and any breast lump should be reported.

Two further points belong here. These medicines reduce measured PSA by about 50%, so the value must be doubled when interpreting it — a man being monitored who does not know this can be falsely reassured ^[1]. And the MHRA has required warnings about depression and suicidal ideation with finasteride ^[5].

On persistent sexual symptoms after stopping — often called post-finasteride syndrome — the honest position is that it is contested. Prescribers should counsel on the possibility. But causal evidence for a lasting post-treatment syndrome is weak, and heavily confounded by nocebo effects and by the fact that most case series are assembled from online communities. Men report it, it is distressing, and the evidence does not currently establish it as a drug effect. Our guide to finasteride side effects covers the same debate in the hair loss context, where the dose is much lower.

The UK pathway

Typical practice, following NICE CG97 and local prescribing guidance ^{[1, 3]}:

1. Assessment — IPSS symptom score, a frequency-volume chart, PSA with counselling, urinalysis, post-void residual and digital rectal examination.
2. Conservative measures for symptoms that are not bothersome.
3. An alpha blocker, reviewed at six weeks and then annually.
4. A 5-alpha reductase inhibitor where the prostate is enlarged, as above.
5. Both together for severe symptoms with significant enlargement.
6. Antimuscarinic or beta-3 agonist medicines where storage and urgency symptoms predominate.
7. A daily low-dose PDE5 inhibitor, one of which is licensed in the UK for benign prostatic enlargement as well as erectile dysfunction — useful where both problems coexist. Our guide to daily versus on-demand dosing explains that regimen.
8. Surgery — TURP, HoLEP, Rezum, UroLift or prostate artery embolisation — where symptoms are refractory or complicated.

The interaction to know about

Combining a daily PDE5 inhibitor with an alpha blocker risks a severe fall in blood pressure. UK guidance is to stop the alpha blocker if starting a daily PDE5 inhibitor for prostate symptoms ^[3]. Combination with a 5-alpha reductase inhibitor is fine.

This is a prescriber decision, and it is one reason a man who has both urinary symptoms and erectile dysfunction is better served by one clinician seeing the whole picture than by two prescriptions arranged separately.

Surgery and ejaculation

TURP — the long-standing standard — causes retrograde ejaculation in around 65–75% of men, and erectile dysfunction in roughly 5–10% ^[2]. The ejaculatory effect is the expected outcome rather than a complication, and it is permanent.

UroLift and Rezum are offered partly on the basis of preserving ejaculation, and UroLift has the better ejaculatory data of the two. The trade-off is that both give less durable symptom relief than TURP, so a younger man weighing them is choosing between preserved ejaculation now and a higher chance of needing something further later.

If fertility matters, say so before any of these decisions. Retrograde ejaculation does not end fertility — sperm can be retrieved — but it changes the route entirely, and our guide to male fertility and sperm health covers the assessment.

What to do if this is happening to you

Do not stop a prescribed medicine on your own. Urinary retention is a genuinely unpleasant emergency, and stopping treatment for prostate symptoms is not a decision to make from a web page.

What to do instead is raise it specifically. Useful things to say: which function has changed — desire, erection, or ejaculation; when it started relative to starting the medicine; and whether it matters enough to you to trade some symptom control for it. Those three pieces of information let a clinician switch within a class, change class, or reconsider the dose.

If erections rather than ejaculation are the problem, that is worth assessing in its own right — erectile dysfunction is an independent cardiovascular risk marker, as our guide to ED and heart disease explains, and attributing it to a prostate tablet can mean missing that.

When to seek help urgently

Inability to pass urine at all is acute urinary retention and needs same-day assessment. Visible blood in the urine needs an urgent GP appointment on the suspected cancer pathway. A breast lump while taking a 5-alpha reductase inhibitor needs prompt review. Our guide to when to see someone about a sexual problem covers the rest.

This article is for general information and isn’t a substitute for advice from your own clinician. If you feel unwell, contact your GP or NHS 111. In an emergency, call 999.