Comparing Viagra / Sildenafil & Cialis / Tadalafil for ED

By: Michael Kemper, M.D.

Erectile dysfunction, or ED, places a significant physical and psychological burden on a man and their partner. Because it is so prevalent and disruptive, there are many options for treatment at every stage of ED. Due to their effectiveness and a great deal of marketing over the past few decades, ED medications like sildenafil, commonly known by its brand name Viagra, and tadalafil, known as Cialis, are the first therapies that pop into most men's minds. They also represent effortless, practical, and straightforward first-line treatment options.

In another post, we will discuss when these medications are most effective and what should be done when they cease to provide reliable and robust erections, but for now, we will compare these two well-known options.

First, it's important to note that both drugs are PDE-5 inhibitors, which relax the muscles in the walls of the blood vessels, dilating them and improving blood flow. Because these drugs are taken orally, they have a systemic effect, and this is why patients can often feel flushed or experience some reddening of the face in addition to improved erectile function. As similar as these drugs may be, there are several differences that should be understood to maximize their effectiveness.

**Note that both drugs are safe for most patients and are generally interchangeable, meaning that if one does not offer the expected result or has unacceptable side effects, the other may be tried in most cases. Some men alternate between them early on to see if one offers better results. Most men find that they work with similar effectiveness when taken as directed.

Duration of Action

Herein lies probably the biggest differentiator between the two drugs. Sildenafil / Viagra has its onset quicker, usually within 30 minutes to an hour, and lasts for several hours. Tadalafil / Cialis has a slower onset of action, 1-2 hours, but lasts longer in the system, up to 36 hours. This means that patients for whom this drug is effective can reasonably expect to achieve an erection spontaneously for a day and a half.

It's important to note here that these medications do not change or improve libido or the desire to have sex. If the desire is not there, a patient will not achieve an erection, no matter which they take. They also do not cause erections spontaneously without foreplay or stimulation. The drug only facilitates the erectile response to sexual stimulation.

Knowing these duration characteristics, we can tailor the medication choice to different lifestyles. For patients in a committed relationship with a predictable sex life, either medication will work. On the other hand, for patients who may have a more spontaneous sex life, the longer duration of action of Cialis / tadalafil may be a better option.

Side Effects

Both drugs can cause similar side effects, which mostly revolve around the dilation of the blood vessels. In both cases, patients may experience flushing or redness in the face. Some may also experience headaches from the increased blood flow. Each medication may affect patients uniquely, and therefore, as mentioned above, they are generally interchangeable, and one may be more suitable from a side effect standpoint than the other.

Some of the more common side effects of sildenafil / Viagra are:

• Headaches
• Nausea
• Flushing
• Congestion
• Indigestion
• Dizziness
• A blue hue in the vision that goes away upon stopping the medication
• Rarely, vision loss which can very rarely lead to permanent blindness

Some common side effects of tadalafil / Cialis are:

• Headaches
• Congestion
• Indigestion
• Back pain
• Cough
• Upper respiratory tract infection

It is worth noting that while most of these side effects are mild, their duration is directly correlated to the medication's half-life. As such, patients who experience side effects from tadalafil will likely experience them for longer than any issues from sildenafil.

Dosage

If you have researched these two drugs, you will notice that they have significantly different maximum dosages. The maximum for sildenafil / Viagra is 100 mg, while the maximum for tadalafil / Cialis is 20 mg. This does not change the effectiveness of the medication. Most patients start at the maximum dose, and then can try using less (a half or quarter tablet) to see if the results are the same.

Interactions with Food

Here again, there is a potentially significant difference between the two. Viagra / sildenafil may be rendered less effective by dietary fat consumed during a meal. It is thus most effective when taken on an empty stomach. This is not the case for Cialis / tadalafil. This often makes the latter the preferred drug for patients who are actively dating, especially those who tend to go out to eat prior to sexual relations.

A Daily Option for Enlarged Prostate

Interestingly, a low dose (5mg) of tadalafil / Cialis can be used daily to aid symptoms from prostatic enlargement or BPH with the additional benefit of improving erectile function. Speak to your urologist to see if this is an option for you. Sildenafil / Viagra does not offer this benefit.

Peak blood concentration

While both medications begin to show effectiveness after 30 to 60 minutes, peak blood concentration is achieved after an hour with sildenafil / Viagra versus 2 hours with tadalafil / Cialis. This should be considered when planning for sexual function.

The Bottom Line

As you can see, while these medications are in the same class and both are safe and effective, they have some significant differences. Fortunately, today, patent expiration and the ubiquitous nature of the generic versions of each have made them far more financially accessible. To that end, we often suggest patients try alternating between the two drugs to see if one works better for their circumstances or has fewer side effects. In some circumstances, they can be combined for a better effect. Most importantly, visit your urologist at the first signs of ED to understand all your available options.

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