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Prostate enlargement and erectile dysfunction (ED) are separate problems. Both increase with age, but one causes problems in the bathroom and the other in the bedroom. However, the two are somewhat linked.

Certain treatments that relieve enlarged prostate can cause ED and other sexual side effects. On the other hand, treating ED can improve enlarged prostate symptoms.

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1. Postsurgical problems
Prostate enlargement can interfere with urination. It can cause sudden urges to urinate, urinary frequency, inability to empty the bladder, or a weak urine stream. A surgery called transurethral resection of the prostate (TURP) can help relieve these symptoms. But, men who have this procedure often experience sexual side effects after surgery.

Between 50 and 75 percent of men experience retrograde ejaculation after TURP. This means that semen released during orgasm enters the bladder rather than exiting the penis. Retrograde ejaculation, sometimes called dry orgasm, is not harmful but can impair male fertility.

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2. BPH Treatment and Erectile Dysfunction
Some men who have the TURP procedure also experience erectile dysfunction, the inability to achieve or maintain an erection. This is not a common side effect of the surgery, but it is possible in 5 to 10 percent of men who have TURP.

Some drugs used to treat BPH can cause difficulty in maintaining an erection. Men who take alpha blockers, which relax bladder and prostate muscle cells, may experience decreased ejaculation. Alpha reductase inhibitors can also cause erectile dysfunction.

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3. Not Now, I Took my BPH Pills
Diminished sex drive is a potential side effect of the BPH medications dutasteride and finasteride, which are both alpha reductase inhibitors. Approximately 3 percent of men who took dutasteride experienced a drop in libido. With finasteride, the incidence of low libido was 6.4 percent.

Men who take these medications may also experience lower sperm count, decreased sperm volume, and lower sperm movement. The drug combination of dutasteride and tamsulosin is associated with low libido in 4.5 percent of men who take it.

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4. Treating ED May Help BPH
Medications that treat erectile dysfunction may help alleviate BPH. The ED drugs sildenafil (Viagra), vardenafil (Levitra), and tadalafil (Cialis) have all been shown to reduce BPH symptoms. However, they aren’t currently approved to treat BPH.

One 12-week study comparing tadalafil and placebo showed that men who took 5 mg of tadalafil daily had significant improvement in both BPH and ED symptom measures.

In an eight-week trial, 108 men who took 10 mg of vardenafil twice daily showed significant improvement in prostate symptoms compared with 113 men who took a placebo. The men were 45 to 64 years old and had a history of BPH.

The study also included men who had ED. The results showed improvement in both BPH and ED symptoms in men who had both conditions.

4. How ED Drugs May Work for BPH
Medications for ED inhibit the enzyme phosphodiesterase-5 (PDE-5). PDE-5 breaks down the chemical cyclic guanosine monophosphate (cGMP). But, cGMP increases blood flow to the penis. So, inhibiting PDE-5 can prevent the breakdown of cGMP. This helps to increase blood flow to the penis.

In theory, ED drugs can boost cGMP levels in the bladder and prostate, as well. The increased cGMP and blood flow may allow bladder and prostate cells to relax, leading to greater urinary flow.  

The studies on ED medication to relieve enlarged prostate symptoms have only looked at short periods of time. And, they only looked at the differences between the ED medications and placebo. The results show promise, but the data is not long-term. The studies have not fully shown that ED drugs are safe and effective to treat urinary symptoms of enlarged prostate.

More evidence is needed from studies that directly compare erectile dysfunction drugs with medications for BPH.

5. Take the Pressure Off
Erectile dysfunction medications lower your blood pressure. If you also take doxazosin or terazosin to manage symptoms of enlarged prostate, talk with your doctor about timing the dosages of your medications.

Doxazosin and terazosin are alpha-1 blockers, which also lower blood pressure. Your doctor may recommend taking the ED and BPH medications at different times of day to avoid dizziness or a steep drop in blood pressure.