Sildenafil vs. tadalafil (and vardenafil): how they differ

Sildenafil (Viagra), tadalafil (Cialis) and vardenafil (Levitra) are the three ED medicines most men get offered first. All three are PDE5 inhibitors. They block an enzyme called PDE5, which lets the blood vessels in the penis stay relaxed and fill with blood when you're aroused. None of them causes an erection on its own; you still need to be turned on.

How long each one lasts

Sildenafil and vardenafil are short-acting. Both labels say to take a dose about an hour before sex, and both drugs have a half-life of around 4 hours, so the useful window is a few hours. The Viagra label allows a dose anywhere from 30 minutes to 4 hours ahead.

Tadalafil stays in the body much longer, with a half-life of about 17.5 hours. One dose can keep erections easier to get for up to 36 hours, which is why some men call it the weekend pill. It's also the only one of the three approved as a low daily dose (2.5 or 5 mg), for men who would rather not plan around a pill at all.

What food does to them

A heavy, high-fat meal slows sildenafil. In the studies behind its label, taking it with a high-fat meal pushed back peak blood levels by about an hour and lowered the peak by 29%. Vardenafil tablets lose some of their peak after a high-fat meal too. Tadalafil is the exception: the label says food doesn't affect how fast or how much of it is absorbed, so you can take it after dinner.

Side effects

Headache, flushing, indigestion and a stuffy nose are common with all three and usually wear off within hours. Sildenafil is the one most likely to change your vision for a while, typically a blue tint or extra sensitivity to light, more so at higher doses. Tadalafil is more often linked to back pain and muscle aches, which tend to show up 12 to 24 hours after a dose and fade within two days.

Who shouldn't take any of them

• Men who take nitrates for chest pain, such as nitroglycerin or isosorbide, or who use nitrite "poppers." The combination can drop blood pressure to a dangerous level.
• Men who take riociguat for pulmonary hypertension.
• Men who have recently had a heart attack or stroke, or whose doctor has said sex isn't safe for their heart.

Tadalafil's long half-life matters in an emergency. Doctors are advised to wait at least 24 hours after sildenafil before giving nitrates, and at least 48 hours after tadalafil, because a study of the interaction still found it at 24 hours and not at 48. If you take either drug and need emergency care for chest pain, tell the staff which one and when. Alpha blockers, used for blood pressure and enlarged prostate, also need care when combined with any of the three. Get medical help right away for an erection that lasts longer than 4 hours.

Picking one

• Sildenafil suits men who are fine planning an hour ahead and taking it on a light stomach. It has the longest track record and is usually the cheapest generic.
• Tadalafil suits men who want a longer window, want to take it with food, or want a daily dose so timing stops being a factor.
• Vardenafil is a reasonable switch if one of the others gives you side effects or doesn't work well enough.

Some men don't get a good enough response from any single drug, which is one reason combination formulas exist. everslim's Quattro combines sildenafil, tadalafil and vardenafil with apomorphine in one dose taken under the tongue. Compounded combinations like this are not FDA-approved and have far less published research behind them than the individual medicines, so whether one makes sense for you is a call for a licensed provider who has your full health history.