Sept. 23, 2002 -- The long-awaited competitor to Viagra -- christened Levitra today -- inches its way to final FDA approval. Two early studies suggest it's longer lasting, has fewer side effects, and is safe for virtually everyone, including those with heart problems. Similar drugs approved in this class of medication carry warnings for men with heart disease.
However, one urologist advises men not to get their hopes up. "That's not to say new drugs won't be exciting and wonderfully worthwhile," Larry Lipshultz, MD, professor of urology at Baylor College of Medicine in Houston. "The data is interesting. Let's see if the drug holds up to the claims."
Levitra was developed by Bayer and GlaxoSmithKline and is scheduled for U.S. launch in 2003.
Viagra, produced by Pfizer Inc., revolutionized the treatment of male sexual dysfunction, allowing men for the first time to pop a pill to get an erection -- rather than trying various devices, having a drug injected into the penis, or having a pellet inserted into it.
By some estimates, some degree of ED affects more than 50% of men over the age of 40. In the U.S., alone 30 million men are affected.
However, statistics show that only about 10% of men seek help. So 90% of men out there still aren't getting treated for impotence, says Irwin Goldstein, MD, director of the Institute for Sexual Medicine at the Boston University Medical Center and a leader of the Massachusetts Male Aging Study.
"In the early days of Viagra, many men got turned off -- largely because reports of heart attacks that were shown later not to be related to the drug," Goldstein tells WebMD. Today, Viagra carries only an advisory for people with high blood pressure who are taking particular types of blood pressure-lowering medication, and patients with angina or heart disease who take nitrates.
The preliminary data on Levitra:
A phase III clinical trial enrolled 440 men with erectile dysfunction between 44 and 77 years old, most of whom had undergone nerve sparing prostatectomies six or more months before entering the study. (About a third of men who have had a prostatectomy -- removal of the prostate gland -- develop ED.) After 12 weeks of Levitra, 71% of the men had improved erections. And a subset of men experiencing depression related to their impotence reported fewer symptoms of depression after taking Levitra.
In a 26-week phase III trial of 805 men, about 74%-77% of men taking 10-20 mg of Levitra reported successful penetration on their first attempt, compared with 46% of men taking placebo. Also, the men who were successful the first time reported successful penetration in about 85%-91% of subsequent attempts, compared with 77% of those taking placebo. Side effects were mild to moderate headache, flushing, and nasal congestion -- "mild stuff," says Goldstein.
Both Viagra and Levitra work by inhibiting the PDE5 enzyme. "That means that if you take a pill, then have sexual stimulation, the drug can magnify the natural erectile response. It allows the reaction to be more like sex should be."
The biochemical differences between the two drugs mark the difference, he says. "Levitra contains a more efficient enzyme inhibitor, so only a very small amount of the drug is necessary," Goldstein tells WebMD. "That's the thing that's cool about Levitra -- it's biochemical potency is distinctly different from Viagra and Cialis [another impotence treatment drug being developed by Lilly]."
All three drugs -- plus several more still in development -- have their place in a physician's armamentarium, says Goldstein. "Several other companies are also working on drugs with PDE5 inhibitors."
When it starts to work and how long it lasts are big issues in impotence medicine: Viagra takes effect in about 30 minutes and the effects last about 4 hours. Cialis reaches maximum concentration in 24 hours, and the effects last for about 3 days, says Goldstein. Levitra is faster-acting, reaching maximum concentration in 30 to 40 minutes, with the effects lasting about 16 hours.
Also, Levitra doesn't carry one disconcerting visual problem that many men report with Viagra: "If you take Viagra, you get a weird blue vision," he says.
Just don't expect miracles with Levitra, says Lipshultz.
"The strength of the drugs will probably be comparable -- they're all supposed to inhibit the enzyme PDE5," Lipshultz tells WebMD. "Whatever dose you take inhibits it completely. So I don't think we're going to be seeing a whole lot of advertising based on 'take this drug because it's stronger.'"
Also, if you didn't have success with Viagra, it's doubtful that Levitra will work any better, says Lipshultz. "I don't think we're going to see people who fail one drug do a whole lot better on another drug. I think where the difference will be -- if any -- is onset of action, duration of action, and side effects."