July 6, 2001 -- Viagra, the little blue pill that made erectile dysfunction household words, may have some serious competition by this time next year when a new long-acting erectile dysfunction drug is expected to hit the market.
In clinical studies the experimental drug, called Cialis, improved erections in 85% of the men taking 20 mg of the drug and the drug's effects last for 24 hours or longer. Viagra usually works for about four hours says Albert Yu, MD, senior director of clinical affairs at ICOS Corporation.
Cialis, pronounced "see-Alice", is being developed as a joint venture between ICOS Corporation and Eli Lilly and Company. Late last week the manufacturers submitted a new drug application to the FDA. If the process goes smoothly "we expect to begin marketing by late in the second quarter of 2002," says ICOS spokesperson Lacy Fitzpatrick.
From former Senator Bob Dole to Playboy founder Hugh Hefner, Viagra proved not only to be an effective treatment but has also caused a sea change in Americans' attitudes about sexual dysfunction. Once considered a taboo subject, erectile dysfunction is now the subject of television, radio, and newspaper advertisements. For NASCAR fans, Viagra sponsors a race team.
Most men experience erection problems at some time in their lives, but about 30 million American men have chronic problems achieving erection. Erectile dysfunction, or ED as it is often called, can affect men at any age but becomes more common with age and 35% of men aged 60 or older have ED.
Considering the size of the market it is not surprising that the makers of Cialis are hoping that lightning will strike twice.
Yu tells WebMD that the new drug is very similar to Viagra, which is known medically as sildenafil. Both drugs, he says, inhibit an enzyme that affects the blood flow to the penis. "By inhibiting this enzyme, PDE5, blood flow is increased," says Yu.
In studies reported at the recent American Urological Association meeting, 78% of men with mild to severe erectile dysfunction were able to complete intercourse after taking 20 g of the drug. Eighty-five percent of the men said they had improved erections, and 63% said they achieved normal erectile function when taking the drug.
Raymond Rosen, PhD, professor of psychiatry at the Robert Wood Johnson Medical School in New Jersey, tells WebMD that no clinical comparison of Viagra and Cialis has been attempted. "So any statements comparing the two are really hypothetical." Rosen is a clinical investigator who has been involved in designing trials of Cialis and other drugs.
Rosen says Cialis "appears to have a rapid onset of action. You get an effect in about 30 minutes and it is effective up to 24 hours or possibly longer."
At this point Rosen says the main advantage of Cialis is this long-acting effect. "People wouldn't have to plan quite as carefully for when they would have intercourse. For example, if a man is planning to be with a partner all day Saturday, he could take the drug in the morning and have intercourse in the afternoon or evening. It's less focused, more natural."
Yu says the new drug appears to be "more specific for PDE5" than Viagra is and this increased specificity means that the drug may cause fewer side effects than Viagra. Yu says that Viagra is generally well tolerated but that some men who take the drug get "blue tinge vision" because the drug also affects an enzyme called PDE6, which is involved in color perception in the eye. "We have not seen any color vision effects," in any men treated in clinical trials says Yu.
Rosen agrees that the drug is well tolerated but he says that a small number of men will complain of headaches, flushing and, in a few cases, low-back pain when taking the drug. "But typically men don't drop out of the studies because of side-effects," says Rosen.
Cialis, like Viagra, should not be taken by men who are taking nitrates, says Yu. "This is because the drug has the same metabolic pathway as nitrates," says Yu. He says, however, that the drug can be taken by men "who take any other type of heart or hypertension medication. There is no contraindication for men with heart disease."