FDA Asked to Approve Once-a-Day Erectile Dysfunction 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."