ProXeed, a citrus-flavored drink powder made by Sigma-Tau Pharmaceuticals Inc. in Gaithersburg, Md., contains two types of carnitine, an amino acid naturally present in the body. It is being sold over the Internet ($570 for the standard six-month regimen) and heavily promoted to urologists and obstetrician-gynecologists.
Although Sigma-Tau cites eight European studies as proof that proXeed improves the number, concentration and swimming ability of sperm, leading American fertility specialists say the studies are too small and poorly designed to put much faith in.
"We really don't know if it works," said Larry Lipshultz, a urologist at Baylor College of Medicine and president of the American Society for Reproductive Medicine.
Nonetheless, after being deluged with patients' inquiries about proXeed, Lipshultz is advising some of them to try it, and monitoring the results. He reasons that proXeed has no side effects, and there isn't much else to offer men with unexplained infertility.
"The only thing that's even close is using clomiphene citrate to alter certain hormones," Lipshultz said. "We really don't have a drug that I could say, 'If you take this, it will help.' So the only thing you have to lose [with proXeed] is the $100 a month you're going to spend. We're offering it to patients with the caveat that we don't know whether it will have any good effects."
Kathryn Go, an embryologist at Pennsylvania Hospital's infertility clinic, agreed, saying "there's not much a man can do for idiopathic low sperm count. ProXeed is so seductive. You think, 'Wow. No injections. You just drink this stuff and you might get some bang for your buck.' "
Infertility, which affects one in 12 couples, has traditionally been thought of as the woman's problem. But studies show a male-related problem is behind 40 percent of infertility cases. An additional 10 percent of cases involve a combination of male and female problems.
Usually, the cause of male infertility can be diagnosed and treated. There may be obstructions, mechanical problems, hormone imbalances, varicose veins around the testicles, or even cancer.
Lifestyle factors also may affect a man's fertility. Drinking, smoking, hot tubs, bodybuilding steroids, certain infections, and even the antibiotics that cure those infections can take a toll on sperm.
Unfortunately, in up to a third of cases, the cause of male infertility simply can't be identified.
"There are so many men who have idiopathic infertility, and the research funding has been horrible," said Lipshultz. "To get a grant to study male infertility . . . is very difficult."
There are plenty of dietary supplements that promise virility and vigor. "Super Male," "Raw Male" and "Male Reproduct Factors" are among products sold over the Internet. There are also products that tout carnitine as a "fat burner."
But proXeed is the only product that flatly claims to be a sperm booster.
How does it work? Scientists know that proXeed's main ingredients, L-carnitine and acetylcarnitine, play a role in cell metabolism. Scientists also know that L-carnitine is highly concentrated in sperm-related tissues, particularly the epididymis, the tubes where sperm finish maturing.
The theory is that men with poor sperm quality lack L-carnitine and acetylcarnitine, so correcting the deficiency will improve the environment where sperm grow. The European studies suggest that taking proXeed for three to six months can improve sperm movement and count.
None of the studies compared men taking proXeed to a control group of men taking a placebo (dummy pills). Nor did the studies look at whether the men went on to father babies.
"That's not what we claim proXeed does," said Brad Stewart, Sigma-Tau's executive director of consumer products. "What it does is optimize sperm quality."
Although Sigma-Tau, headquartered in Italy, began pitching proXeed to consumers less than two months ago, it has marketed L-carnitine as a prescription drug called Carnitor for about a decade in the United States. The drug is approved to treat carnitine deficiency, a rare metabolic disorder.
Stewart defended the quality of the European studies of proXeed, but said a large, randomized, placebo-controlled study - the gold standard of clinical trials - was underway at the University of Minnesota and Brown University.