The array of erectile dysfunction medications on the market these days can present a challenge for guys just trying to understand what, where, and how they should begin treatment.

The first thing to understand is that all of the FDA-approved ED meds have demonstrated safety and effectiveness in clinical trials and have been used by millions of men in the last decade. Quality ED meds are not available OTC, and Viagra and Cialis are two of the most popular options – for good reason – available affordably and simply. 

Quick Facts About Cialis And Viagra

Viagra (sildenafil) and Cialis (tadalafil) are both PDE5 inhibitors approved to treat erectile dysfunction.

Viagra was approved in 1998, Cialis in 2003, and both are available as generics today.

Cialis is known for a longer window for sexual intimacy (up to 36 hours vs 4 hours for Viagra), as well as a lower dose that can be taken every day to prepare you for intimacy at any time.

Viagra And Cialis Work The Same Way

Viagra is the brand name for sildenafil, a drug discovered by chemists at Pfizer. Viagra is a PDE5 inhibitor that helps to relax the smooth muscles in the penis, promote blood flow, and help to cause erections.

Cialis is the brand name for tadalafil, another PDE5 inhibitor developed by scientists at Eli Lilly around the same time.

Both ED meds are effective at treating ED in men of all ages, though there are some nuances to these two popular ED meds.

Phosphodiesterase type-5 (PDE5) inhibitors work by removing the brakes on the erection process. PDE5 is an enzyme that breaks down cGMP, a peptide that helps to relax blood vessel walls and improve blood flow. By inhibiting PDE5, these inhibitors (sildenafil, tadalafil, etc.) let cGMP continue to do its job in the penis: improving blood flow and causing an erection. They're effective in more than 80% of men.

Which Came First, Viagra Or Cialis?

In 1998, Viagra became the first PDE5 inhibitor approved by the U.S. FDA for ED. Cialis was in development at the same time, but it wasn't approved until 2003. In fact, while these two medications are considered the best-known and most-popular of the ED medications in the U.S., Cialis was actually third to market. Levitra (vardenafil) was approved by the FDA just a few months before Cialis in 2003, making Cialis third to market in a very popular and highly lucrative space.

Until Viagra's approval in 1998, ED had no great treatment options and wasn't a common point of discussion (for obvious reasons, guys). But with a strong promotional effort in the late '90s, Pfizer and then El Lilly helped to make ED – and medicines that could resolve ED – mainstream. Viagra famously enlisted spokesmen in soccer legend Pele and former presidential nominee Bob Dole.

Is Viagra Or Cialis More Effective?

When choosing between Cialis and Viagra, effectiveness shouldn't be a concern for most men – these PDE5 inhibitors are mostly the same in terms of effectiveness. A 2005 paper indicated that Viagra works in about 84% of men, and Cialis in about 81%. While there's the chance that some men will react differently to these medications and may indeed need to try more than one, your decision should be based mostly on what your doctor recommends and some more important preferences.

Both medications require some sexual stimulation to get things started; just taking the medication and then sitting around waiting isn't likely to work for most men. Both medications also recommend a maximum frequency of no more than once daily.

The big difference between Cialis and Viagra is in the window for sexual intimacy.

Cialis Lasts Longer Than Viagra

As you probably already know, Viagra and Cialis are both taken prior to sexual intimacy. Viagra's FDA prescribing label indicates that it can be taken up to 4 hours before intimacy. It takes 30-60 minutes to start working, but any time in that window men can expect some stimulation to cause an erection.

Cialis has a much longer window for intimacy: up to 36 hours. That's a big deal for a lot of men, who don't want to have to plan too far in advance when they take their medication. Men can take Cialis on a Tuesday morning and still expect to see some effect even Wednesday afternoon according to its manufacturer.

In addition, Cialis is also available as a lower dose that can be taken once every day in order to prepare you for sexual intimacy at any time.

What Are The Available Doses Of Cialis And Viagra

Viagra and generic sildenafil are available in doses of 25 mg, 50 mg, and 100 mg.

Cialis and generic tadalafil are available in doses of 2.5 mg, 5 mg, 10 mg, and 20 mg. Cialis was first approved at 5,10 and 20 mg for on-demand treatment of ED, but a few years after its initial approval in 2003, Eli Lilly got another approval for a once-daily regimen at 2.5 mg or 5 mg.

Sildenafil is also available in a 20 mg tablet. Because of its effects on blood pressure, Pfizer pursued its testing in Pulmonary Arterial Hypertension (PAH), where it is now approved by the FDA under the brand name Revatio.

This 20mg tablet has been used by some doctors and men for the treatment of ED too, with dosing increments created by combining more than one pill. In years past, generic sildenafil 20 mg was sometimes cheaper than alternatives at the approved ED doses of 25, 50, and 100 mg. Today, Rex MD is proud to offer all sildenafil doses at great prices – you don't need to mix five 20 mg sildenafil tablet to equal a 100mg dose.

Which Dose For You?

Most men begin treatment with Viagra at 25 mg or 50 mg, allowing them to try out its effectiveness and adjust accordingly. Men who don't respond sufficiently on either of these low doses can then get a new prescription for a higher dose.

Most men begin Cialis at 5 mg or 10 mg and can titrate higher from there if necessary.

Both of these are taken "on demand" in the hours or day before sex.

Some men may find that they'd rather take a pill every day rather than try to time their sex life. A once-daily low dose of Cialis is a compelling option in this case. Rather than plan ahead and take Cialis in the hours before sex, men can take 2.5 or 5 mg Cialis one every day in order to prime their system for sex any time. The Cialis label indicates this option may be good for men who anticipate sexual intimacy more than a few times a week.

Side Effects Of Cialis And Viagra

PDE5 inhibitors have been around for more than 20 years and taken by millions of men – their side effect profile is pretty well defined.

Viagra's most common mild side effects include headache, facial flushing, dyspepsia, nasal congestion, abnormal vision, back pain, dizziness, and rash. Less common adverse reactions (in <2% of patients during clinical trials) included heart-attack symptoms, sudden vision problems, seizures, prolonged erection, and priapism. For full details see the Viagra prescribing label.

Cialis' most common mild side effects include headaches, dyspepsia, nasopharyngitis, back pain, respiratory infection, flushing, and limb pain. Less common reactions in <2% of patients included chest pain, sudden decrease in hearing, tinnitus, face edema, blurred vision, and some others. For full details, see the FDA's approved Cialis label.

Importantly, patients considering Viagra or Cialis should not take either if they are already taking nitrates or alpha-blockers, take riociguat, have high or low blood pressure, are allergic to sildenafil or tadalafil, or are not healthy enough for sexual activity. 

Before taking either medication, make sure to connect with a doctor about what's right for you.

Which Should You Take, Cialis Or Viagra?

Men will find that one or another of these ED medications will work for them, but Cialis (tadalafil) has become a strong contender for most men considering the larger window of opportunity (36 hours). And, Cialis Daily (low-dose tadalafil) is a popular option for men who want to have sex more often and with less pill-popping hassle.

Guys may also find that one of these options doesn't agree with them based on side effects, which a doctor can help you determine after first diagnosis and treatment.

We at Rex MD have found that Viagra 50mg and Cialis Daily are two of our most popular options for men to begin ED treatment; and, if approved through our virtual visit process, it's easy to get started and change medications if you're not fully satisfied.