Ask the Doctors by Eve Glazier, M.D. and Elizabeth Ko, M.D

Studies Show PDE5 Inhibitors to Be Effective in Treating BPH

Dear Doctor: What is your opinion of using Cialis to treat benign prostatic hyperplasia? And what should the dosage be?

Dear Reader: Cialis (tadalafil) may be most familiar as an effective drug for erectile dysfunction, similar to other drugs in its class, such as Viagra and Levitra. Because its chemical structure is different, however, it lasts longer in the bloodstream. In simple terms, tadalafil works by inhibiting a specific enzyme, PDE5, and in doing so increases blood flow.

Epidemiologic studies have noted an association between erectile dysfunction and the lower urinary tract symptoms of benign prostatic hyperplasia (BPH), also known as an enlarged prostate. Those symptoms include urinary frequency, urgency, hesitancy and poor stream. Accordingly, PDE5 inhibitors have the potential to help treat not only erectile dysfunction but also BPH.

As for studies assessing the use of Cialis, Viagra and Levitra for BPH, the results have been fairly promising. A 2011 analysis of 11 studies looked at the benefits of PDE5 inhibitors compared with a placebo. Six of the studies used Cialis, four used Viagra and one used Levitra. Participants filled out a questionnaire prior to starting the studies, which lasted eight to 12 weeks, and again at the end. The trials found that the reported symptoms of BPH improved with each of the medications compared to placebo. However, none of the five studies actually assessing urine flow found an improvement with the PDE5 inhibitors, and four failed to show an improvement in the emptying of the bladder.

Later studies, with the use of Cialis specifically, also verified a reduction in urinary symptoms. The greatest benefit came from the use of 5 milligrams of Cialis on a daily basis, with 60 to 79 percent of participants reporting an improvement of symptoms, and more than 50 percent noting an improvement after one week.

A 2012 study in the journal European Urology compared Cialis with the most commonly used drug for BPH, Flomax: 171 patients took Cialis and 167 patients took Flomax. Researchers found significant and near equal improvement of most urinary symptoms. But Cialis didn't improve urine flow, as did Flomax and other alpha-1 blockers. That said, Flomax does not benefit erections.

It might be tempting to combine an alpha-1 blocker like Flomax with Cialis, but the two medications together have the potential to severely lower blood pressure. That's not to say they will, however. A recent 2017 study, which assessed that specific combination, did not show any significant adverse effects. Clearly, more studies are needed to know if the combination is safe and any better than Flomax alone.

If you have erectile dysfunction and symptoms of enlarged prostate, Cialis can benefit both of those problems. A daily dose of 5 milligrams should be effective, with about 70 percent of people seeing improvement of urinary symptoms at four weeks.

Please note that a recent column on the potential link between peripheral neuropathy and MRI with gadolinium contrast was unclear on the use of an iodine contrast agent. The latter is administered with a CT scan, not MRI, and should be used with caution in those with kidney dysfunction.

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