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BPH Medications and Side Effects: Tamsulosin, Finasteride and More

Written by David Shusterman, MD, board-certified urologist, adapted from his book Shrink the Prostate. General information, not medical advice for your situation. Who publishes this site.

The two main types of medication for an enlarged prostate (BPH) are alpha-blockers, such as tamsulosin (Flomax), which relax muscle to ease urine flow within days, and 5-alpha-reductase inhibitors, such as finasteride (Proscar), which slowly shrink the prostate over months. Both can help, but neither removes the blockage, and both have side effects, including effects on ejaculation, erections and libido. They work best as a measured, time-limited trial with a clear plan for what comes next.

Alpha-blockers: tamsulosin, alfuzosin and silodosin

Alpha-blockers include tamsulosin (Flomax), alfuzosin (Uroxatral) and silodosin (Rapaflo). They relax the smooth muscle in the prostate and at the bladder neck, which lowers resistance so urine flows more easily. Many men feel a difference within days.

What they do not do is shrink the prostate or slow the disease. They treat symptoms, not the structure. When you stop taking them, symptoms tend to come back quickly.

Common side effects include:

• Dizziness or lightheadedness when standing up (orthostatic hypotension), which raises the risk of falls in older men.
• Ejaculation changes, including retrograde ejaculation, where semen goes backward into the bladder instead of out.
• Nasal congestion, tiredness, headaches and a hard-to-describe mental fog.

Many men stop alpha-blockers not because they did nothing, but because the side effects made them feel worse than the condition.

5-alpha-reductase inhibitors: finasteride and dutasteride

Finasteride (Proscar) and dutasteride (Avodart) block the conversion of testosterone into DHT, the hormone that drives prostate growth. Over six to twelve months, they can shrink the prostate by up to about 25%.

The trade-off is mostly sexual and hormonal. Reported side effects include:

• Lower sex drive (libido)
• Erectile dysfunction
• Less semen, and delayed or absent orgasm
• Depression, a link reported in several studies, especially in younger men

For most men these effects ease after stopping, but some report problems that persist, sometimes called post-finasteride syndrome. It is still debated in medicine, but men deserve to know about it before starting long-term use.

One more important point: these drugs can lower PSA levels by up to about 50%. That can hide or delay the diagnosis of prostate cancer if no one adjusts for it. Always tell any doctor checking your PSA that you take finasteride or dutasteride.

Combination therapy, tadalafil and supplements

Combination therapy uses an alpha-blocker and a 5-alpha-reductase inhibitor together. It can work better than either drug alone, but the side effects add up, and many men find it hard to stay on.

Tadalafil (Cialis), an erectile dysfunction drug, also has an FDA indication for BPH. For a man with both mild urinary symptoms and mild erection problems, one daily pill for both can be a reasonable choice. Its effect on flow is modest, usually weaker than tamsulosin, and it does not shrink the prostate.

Saw palmetto and other prostate supplements are popular, but the best large, placebo-controlled trials found saw palmetto worked no better than a sugar pill for symptoms, flow or prostate size. The real cost of supplements is often time: years that feel like action while the prostate keeps growing and the bladder keeps straining.

How well BPH pills actually work

In clinical trials, these medications lower the IPSS symptom score by about 3 to 6 points on a 35-point scale. That might move a man from “moderate” to “mild,” but it rarely brings him back to normal, and the improvement tends to level off rather than keep growing. For comparison, procedures such as prostate artery embolization (PAE) lower the score by about 12 to 20 points.

Staying on the pills is also hard. Research shows that most men prescribed BPH medication stop within one to two years, often because of side effects, too little benefit or cost. Even on combination therapy, studies show up to 30 to 40% of men progress within five years to the point where medication is no longer enough.

Missing doses matters too. Some men go into acute urinary retention, being suddenly unable to urinate, after skipping their medication for a few days while traveling. Do not stop or change a BPH medication without talking to your doctor.

Use medication as a bridge with a plan

Medication is not wrong. Used well, it is a valuable tool. The problem is a prescription with no plan. A better approach:

• Before starting, record your IPSS score, flow rate, post-void residual and prostate size.
• Re-measure after six to twelve weeks.
• Agree in advance on what happens if the numbers have not improved or the side effects are not worth it.

A useful rule of thumb: a medication that is not measurably working by about three months is not working. Staying the course at that point is not caution; it is delay.

Signs your medication is no longer enough

• Your stream keeps getting weaker even though you take the pills every day.
• Bladder scans show more urine left behind after you go.
• Urgency gets worse or leaks begin.
• Urinary infections keep coming back.
• Bladder stones or blood in the urine appear.
• You have an episode of being unable to urinate.

If any of these happen, talk to a urologist about the next step. Waiting too long lets the bladder muscle weaken in ways that may not fully recover. Options from least invasive to most are covered in enlarged prostate (BPH) treatment options, including PAE as a first-line procedure.

This article is general information, not advice about your own prescriptions. Your doctor can help you weigh the benefits and side effects for your situation.

Frequently asked questions

What are the side effects of tamsulosin?

Common side effects include dizziness when standing, ejaculation changes such as retrograde ejaculation, nasal congestion, tiredness and headaches.

Does finasteride shrink the prostate?

Yes, slowly. Finasteride and dutasteride can shrink the prostate by up to about 25% over six to twelve months. They can also lower sex drive, cause erectile problems and reduce semen.

Does finasteride affect PSA tests?

Yes. Finasteride and dutasteride can lower PSA by up to about 50%, which can hide prostate cancer if it is not taken into account. Tell any doctor checking your PSA that you take them.

Does saw palmetto work for an enlarged prostate?

The best large, placebo-controlled trials found saw palmetto worked no better than a sugar pill for urinary symptoms, flow or prostate size.

How long should I try BPH medication?

Re-measure your symptom score and flow after six to twelve weeks. If the medication is not measurably working by about three months, talk to a urologist about the next step.