Viagra and other oral erectile dysfunction medications may help to improve male fertility. A Chinese study found that the drugs improved both the quality and motility of sperm.
Oral erectile dysfunction drugs, known collectively as PDE5 inhibitors, appear to be emerging as yet another weapon in the fight against male infertility. A recent Chinese review of published research studies offers evidence that these medications improve the quality of sperm in men who have been diagnosed as infertile because of low sperm count.
Having a low sperm count — less than 15 million sperm per milliliter of semen — decreases a man’s odds of successfully fertilizing the egg of his female partner, thus creating a pregnancy. Further decreasing the odds of achieving pregnancy, many of these men with low sperm count also produced sperm that failed to move as spontaneously and purposefully as it should and that was abnormally shaped.
Evaluating Sperm Quality
Together with sperm count, the motility and morphology of sperm are the three most critical parameters in determining a man’s fertility. Motility covers not only the ability of the sperm to move but also encompasses the patterns of its movement, while morphology refers to the sperm’s size and shape.
The Chinese research review was conducted by urology researchers at China’s Sichuan University, which is located in Chengdu, capital of Sichuan province. Findings from the review were published in the July 2017 issue of “Urology.”
As part of their review, Sichuan University urologists searched for relevant studies that offered sufficient data for quantitative analysis. They identified a total of 11 such studies, which covered just over 1,300 male participants, many of whom were diagnosed as infertile on the basis of low sperm count.
Sperm Analyzed
In all of the studies analyzed, male participants were given an oral ED drug, after which the sperm they produced was analyzed in terms of semen volume, sperm concentration, motility, and morphology. The studies showed that taking an ED drug had no apparent effect on either semen volume or sperm concentration. However, both the motility and morphology of participants’ sperm improved after taking one of the ED drugs.
As previously noted, motility is the ability of the sperm to move. However, it is further broken down to indicate whether the movement of analyzed sperm is purposeful or not. Progressive motility indicates that the sperm is moving generally forward in a line or in a broad circular pattern, and rapid progressive motility indicates that the sperm is moving rapidly in a purposeful direction.
More Motile Sperm Produced
In the wake of dosing with PDE5 inhibitors, infertile men produced a greater percentage of motile sperm. More significantly, the percentages of total progressive motility and rapid progressive motility increased significantly. Infertile men who were given oral ED drugs also produced a higher percentage of sperm that was normal in both size and shape.
While the PDE5 inhibitors improved the quality of sperm in men considered infertile, they produced no significant changes in the sperm of men considered normal in terms of fertility. This finding that PDE5 inhibitors have no effect on the sperm of normal men is consistent with the conclusion of a 2002 study showing that taking 100 milligrams of sildenafil, the active ingredient in Viagra, had no effect on sperm function or ejaculate quality in fertile men.
Contradictory Findings
However, the conclusions drawn in the Chinese research review are at odds with the findings of a laboratory study conducted at Queen’s University in Northern Ireland. For the Irish study study, researchers collected sperm samples from 45 men attending a fertility clinic in Belfast. Roughly half of the samples were treated with sildenafil in vitro, while the other half were set aside as control samples.
David Glenn, a member of the Queen’s University research team, told NewScientist.com that sildenafil increased the motility of sperm but also appeared to trigger a premature activation of the sperm’s acrosome reaction. This reaction, key to successfully impregnating a female egg, occurs when digestive enzymes at the head of the sperm break away to penetrate the outer wall of the egg, thus allowing the sperm to enter.
How ED Drugs Work
Introduced in 1998, Viagra was the first of the PDE5 inhibitors, so called for their ability to temporarily sideline the phosphodiesterase-5 enzyme, which can interfere with optimal blood flow to the penis. By holding the PDE5 enzyme at bay, these drugs, which also include Levitra, Cialis, Staxyn, and Stendra, allow a key player in erectile function to optimize blood flow to the penis. That key player is cyclic guanosine monophosphate, or cGMP, which also appears to play a determinative role in sperm motility.
Effects of Nitric Oxide on Motility
A study published in the January 2011 issue of “Reproduction,” found that nitric oxide stimulates sperm motility by activating soluble guanylate cyclase, which in turn triggers the synthesis of cGMP and activates cGMP-dependent protein kinases.
Because findings about the effects of PDE5 inhibitors on male fertility are somewhat contradictory, further studies, preferably broader in scope, will be needed to produce definitive proof one way or the other.
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