Approved by the FDA in 1998, sildenafil (Viagra) revolutionized the way we think about — and treat — erectile dysfunction (ED), largely because it is effective and easy to use. In 2003, the FDA approved two closely related drugs, vardenafil (Levitra) and tadalafil (Cialis). Five years later, in January 2008, low-dose Cialis for daily use came onto the market, creating an option that — theoretically, at least — makes having sex a possibility without advance planning.All three drugs work in a similar fashion, by affecting the normal physiology of the penis.
In particular, they block PDE5, an enzyme that breaks down the erection-producing chemical cyclic guanosine monophosphate. This enables the penis to fill with blood and to stay erect long enough for intercourse. Of course, it’s important to realize that none of these drugs is an aphrodisiac. You must feel sexually aroused in order for them to work.The main differences between the three drugs have to do with timing: how quickly they begin to work, and how long their effects last (see Table 4). The biggest divide lies between Cialis for daily use, which keeps a steady supply of the drug in the bloodstream, and the as-needed dosing offered by the original form of Cialis, as well as by Levitra and Viagra.
Among the nondaily pills, Levitra may start working slightly faster than Viagra (within a half-hour instead of an hour) although the FDA says that like Viagra, it should be taken about an hour before sexual activity. Some studies suggest that Levitra may help some men who don’t respond to Viagra. And while some doctors are skeptical about this claim, there’s no harm in trying Levitra or Cialis if Viagra doesn’t work for you.
Cialis stays active in the body much longer than the other drugs. Viagra and Levitra last about four to five hours (and sometimes up to 12 hours). But with Cialis, the window of opportunity ranges from 24 to 36 hours, which is why it’s sometimes called “the weekend drug.” The low-dose daily option aims to allow a man to be prepared for sex anytime (see “Why take a daily ED pill?”). Another difference among the three drugs is that while Viagra’s action may be delayed or impaired when taken with food (especially high-fat foods), that’s not the case with Levitra or Cialis.
Viagra causes erections only during sexual excitement. It does not work in the absence of arousal.
You should not take Viagra if you have been instructed by your doctor not to engage in sexual activity due to heart disease or other heart problems. Viagra must never be used by men who are taking medicines that contain nitrates of any kind. If you take Viagra with any nitrate medicine your blood pressure could suddenly drop to an unsafe or life-threatening level.
Viagra does not cure erectile dysfunction and it does not protect you or your partner from acquiring any sexually transmitted diseases.
Stop any sexual activity if you experience any chest pain, dizziness, or nausea during sex and get medical help immediately. Sex may put strain on your heart, especially if it is already weak from heart disease.
If an erection lasts for a long time, it can permanently damage your penis. You should call a doctor immediately if you ever have a prolonged erection that lasts >4 hours.
Viagra may rarely cause mild but temporary vision changes such as blurred vision or it may give a blue/green color tint to vision. Contact your doctor if vision changes occur.
Sudden loss or decrease in hearing, sometimes with ringing in the ears and dizziness, has been rarely reported in people taking Viagra. If you experience these symptoms, stop taking Viagra and contact a doctor right away. Who should not take Viagra? Viagra is not intended for use by women.
If you take Viagra with any nitrate medicine, your blood pressure could suddenly drop to an unsafe level. You could get dizzy, faint, or even have a heart attack or stroke.