Prostate Medications: What Each One Actually Does

We have written repeatedly on this site that prescription treatments for an enlarged prostate have evidence behind them that no supplement in the category comes close to matching. That is true, and until now we have never said what those treatments actually are.

This page fixes that. It is not a recommendation to take anything — that is a conversation with a clinician who knows your history. It is a description of what is on the table, so that the conversation starts from something better than a blank page.

It is part of our complete guide to an enlarged prostate after 40.

What are the two main prostate medications?

Almost everything prescribed for benign enlargement belongs to one of two families, and the difference between them is not a matter of strength. They do genuinely different things to genuinely different parts of the problem.

The prostate wraps around the urethra. Symptoms arise partly because the gland has grown and is pressing inward, and partly because the smooth muscle in the prostate and bladder neck is holding that passage tight. One drug family addresses the muscle; the other addresses the tissue.

Reading down that table explains most of what happens in practice. A man who wants relief this month is offered the first column. A man with a large prostate and a long horizon is offered the second, or both.

Alpha blockers: fast, but they change nothing underneath

These relax muscle. They do not touch the size of the gland, which means they treat the experience of the condition rather than the condition. That is not a criticism — the experience is what sent you to the doctor — but it does explain their pattern of use.

The speed is their strongest feature. Most men notice a difference within a week or two, which also makes them easy to evaluate honestly: if nothing has changed after a month, the answer is not to wait longer.

The side effects worth knowing before you start:

• Retrograde ejaculation. Semen passes backwards into the bladder rather than out. It is harmless, it is common with tamsulosin and silodosin, and it is startling if nobody warned you. It reverses when the drug is stopped.
• Dizziness on standing. More pronounced with the older, less selective drugs such as doxazosin and terazosin, which also lower blood pressure. This is why a first dose is often taken at bedtime.
• Nasal congestion and tiredness. Usually mild and often settles.

Finasteride and dutasteride: slow, and the only ones that change the course

These block the conversion of testosterone into dihydrotestosterone, the hormone that drives prostate growth. Deprived of it, the gland gradually shrinks — typically by around a fifth to a quarter over six to twelve months.

The consequence is the one thing an alpha blocker cannot offer. Because the prostate is genuinely smaller, these drugs reduce the risk of acute urinary retention and the likelihood of eventually needing surgery. They alter where the condition is heading rather than only how it feels today.

The price is patience. Nothing meaningful happens in the first month, and a man who judges the drug at six weeks will conclude, wrongly, that it does not work. They are also more useful in men with a genuinely large prostate; in a small gland there is less to shrink.

Which one would you be offered first?

For most men with moderate symptoms and an average-sized prostate, an alpha blocker. It works quickly, the effect is obvious, and if it does not help you have learned something within a fortnight rather than half a year.

A 5-alpha-reductase inhibitor becomes the more logical starting point when the prostate is clearly enlarged on examination or scanning, when the concern is the direction of travel rather than today's discomfort, or when a man has already had an episode of retention.

Neither is a first resort in the sense of being unavoidable. Symptoms that are genuinely mild are often managed without any drug at all, which is covered in my prostate symptoms are mild. The decision depends on your symptom score, your prostate size and what bothers you, which is why the assessment comes before the prescription.

The side effects men actually want to know about

It is worth being direct, because this is the question most men have and the one they are least likely to ask out loud.

With alpha blockers, the common sexual effect is ejaculatory rather than erectile: less semen, or none, because it is going into the bladder. Erections are generally unaffected. It sounds worse than most men find it, and it stops when the drug stops.

With finasteride and dutasteride the picture is different and deserves an honest account. In trials, reduced libido, erectile difficulty and ejaculatory problems each occurred in a single-digit percentage of men, modestly above the rate in the placebo groups. Most men taking these drugs do not experience them. A minority clearly do.

A side effect that affects a small percentage of men affects one hundred percent of the man it happens to. Both of those statements are true and neither cancels the other.

There is also a continuing debate about symptoms that some men report persisting after stopping the drug. It is contested, the evidence is unsettled, and we are not going to tell you it is definitely real or definitely not. What we will say is that it is a reasonable thing to raise with a prescriber, and that a doctor who dismisses the question rather than discussing it is not giving you what you came for.

Breast tenderness or enlargement is an uncommon but recognised effect of the second class, and any new breast lump should be examined rather than watched.

What these drugs do to your PSA

This is the single most practically important interaction on the page, and it is missed constantly.

Finasteride and dutasteride roughly halve PSA after six to twelve months of treatment. A clinician who knows you take one will typically double the measured figure before interpreting it. A clinician who does not know may read a genuinely raised result as a comfortably normal one.

The trap that catches most men is dose. Finasteride is prescribed at 5 mg for the prostate and at 1 mg for hair loss, and the 1 mg version lowers PSA as well. A man who has taken it for years for his hairline may not think of it as a prostate drug at all, and will not mention it. What the number means, and what else moves it, is covered in PSA levels by age.

Taking both together

Combination therapy is common and well studied. The logic is straightforward: the alpha blocker handles the next fortnight while the second drug works on the next year.

In men with larger prostates, the combination outperforms either drug used alone at reducing symptoms and at lowering the risk of the condition progressing. The trade-off is equally straightforward: you accumulate the side effects of both.

Some men on combination treatment eventually stop the alpha blocker once the second drug has had time to shrink the gland. That is a planned step rather than something to try unilaterally.

What else gets prescribed

Two other options come up often enough to be worth recognising.

1. Daily low-dose tadalafil. The drug better known for erectile dysfunction is also licensed for the urinary symptoms of an enlarged prostate. It is a sensible option for a man dealing with both, which is a large overlap.
2. Bladder-directed drugs. Where the dominant complaint is urgency and frequency rather than a weak stream, medication aimed at the bladder rather than the prostate may be more appropriate. This is the storage-versus-voiding distinction set out in waking up to pee at night.

Beyond medication there are procedures, from established surgery to newer minimally invasive options. They are outside the scope of this page, and they are a specialist conversation rather than a first step.

How to tell whether it is actually working

This is where most drug trials at home go wrong, and it is the same failure this site has described about supplements: judging by impression rather than by measurement.

The fix costs five minutes. Complete the standard seven-question symptom score on the day you start, write the total down with the date, and keep a count of night-time trips for a week. You now have a baseline, and every later judgement has something to be compared against.

Then use the checkpoint that matches the drug rather than the calendar:

1. Alpha blocker: four weeks. By then the drug has done whatever it is going to do. Score again. If the number has not moved, it has not worked, and continuing on hope is exactly the mistake the supplement industry relies on.
2. Finasteride or dutasteride: three months at the earliest, six for a fair verdict. Anything before three months measures your patience, not the drug.
3. Either drug, at any point: a new side effect. That is a reason to go back and discuss, not a reason to stop silently.

There is a second reason to keep the numbers, and it outlasts the prescription. If you eventually see a specialist, two symptom scores taken six months apart tell them something that no amount of describing can. The method is the same one set out in how long prostate supplements take to work — and it is worth more here, because this time there is a real effect to detect.

What happens if you stop

Neither drug cures anything, so symptoms generally return. How fast depends on which one you stopped.

An alpha blocker wears off within days, because the muscle it was relaxing simply stops being relaxed. A 5-alpha-reductase inhibitor unwinds slowly: the prostate regrows over months, and PSA drifts back up as it does, which can look alarming on a result sheet if nobody has explained why.

One thing worth carrying away from all of this: unlike the supplements this site has written about at length, these drugs have effects large enough and consistent enough to show up against placebo in large trials. That is the entire difference, and it cuts both ways — it is also why they have side effects worth discussing. Something with no measurable benefit rarely has much of a downside either, which is covered in what the Cochrane review found on saw palmetto.