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Fact Checked

Cialis vs Viagra: What's the difference?

More than 30 million American men suffer from erectile dysfunction (male impotence) or benign prostatic hyperplasia (enlarged prostate). These conditions can cause shame, frustration, and discomfort for many men, but since the late 1990s, quality prescription treatment options, including Cialis and Viagra, have been available. Although prohibitively expensive for many people until the release of generic versions of the drugs several years ago, Cialis and Viagra (active ingredient sildenafil citrate) are considered wonder drugs for the people who need them. Cialis and Viagra can both be used to treat erectile dysfunction (ed) and benign prostatic hyperplasia (bph), but the medications are not interchangeable, and there are some key differences between the two drugs.

Drug Class

Cialis and Viagra both belong to a class of drugs called phosphodiesterase inhibitors, which are used to treat sexual dysfunction in men. Viagra became the first prescription drug marketed to treat erectile dysfunction from this class when it was approved by the U.S. Food and Drug Administration (FDA) in 1998. Cialis was approved by the FDA in 2003, providing an alternative to Viagra for the first time. Only the brand name forms of the drugs were available for many years, but today, Cialis is now sold under the generic name tadalafil and generic Viagra is sold under the name sildenafil.  

Conditions Treated

Both Viagra and Cialis are used to treat erectile dysfunction and benign prostatic hyperplasia, or an enlarged prostate, in adult men. 

Erectile Dysfunction

Erectile dysfunction, or male impotence, is a condition in which men have difficulty getting and/or maintaining an erection due to limited blood flow or low blood pressure to the penis, resulting in decreased sexual stimulation or sexual activity. Erectile dysfunction can be caused by physical, psychological, and lifestyle factors, so the condition is complicated to treat.  The five physical conditions most likely to cause erectile dysfunction are atherosclerosis (clogged arteries), high blood pressure, high cholesterol, diabetes, and obesity. The five lifestyle factors most likely to influence erectile dysfunction are alcohol abuse, smoking, illegal drug use, common side effects of other prescription medications, and side effects of over-the-counter medications. Men dealing with psychological issues such as depression, stress, and anxiety also may suffer from erectile dysfunction. Erectile dysfunction can be a sign of a serious health issue and should be discussed with your doctor for medical advice.

Benign Prostatic Hyperplasia

Benign prostatic hyperplasia is a common condition that is increasingly likely to occur as men age. An enlarged prostate can result in uncomfortable urinary symptoms, such as the blocking of urine flow from the bladder. Men with benign prostatic hyperplasia may experience a frequent or urgent need to urinate, increased frequency of urination at night, difficulty urinating, a weak urine stream, a urine stream that stops and starts, or inability to completely empty the bladder. If left untreated, bladder, urinary tract, and kidney problems may also occur. 

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How it Works

Cialis and Viagra work by working as a pde5 inhibitor, that causes blood to flow out of an erect penis. During an erection, a chemical called cGMP causes the tissues and muscles in the penis to relax, allowing blood to flow in. Blood gets trapped inside the penis, causing an erection. Normally,  the trapped blood would eventually release, the erection would subside, and blood flow would return to normal after sexual intercourse, but men with erectile dysfunction have difficulty keeping blood inside the penis. Viagra and Cialis work by blocking Phosphodiesterase-5, which is a chemical that causes the breakdown of cGMP. Without the action of PDE-5, the cGMP does not get broken down and the tissues in the penis stay relaxed and engorged with blood, allowing men to keep an erection. The medications only work when an individual is sexually stimulated. 


Dosing

Cialis

Cialis is manufactured in 2.5 mg, 5 mg, 10 mg, or 20 mg oral tablets. The average starting dose of Cialis for erectile dysfunction is generally 10 mg, but your doctor will prescribe the right dose for you based on the severity of the condition being treated, your age, medical history, and other factors. Some people take Cialis on an as-needed basis; these individuals are likely to take the 10 mg or 20 mg tablets for use before sex. Men who take Cialis every day generally take a dose of 2.5 mg or 5 mg per day. 

Viagra

Viagra is produced in oral tablets with a strength of 20 mg, but prescriptions are written for a variety of doses.  The appropriate dose of Viagra depends on several factors, including the condition being treated, your age, height, and weight, and the severity of your condition; erectile dysfunction  is treated with dosages ranging from 20 to 100 mg. The starting dose for ed medications is typically 50 mg, but your doctor may start you at a dose higher or lower than this initially based on your needs.

Use

One major difference between Cialis and Viagra is in how the medications are used. Cialis can be taken just 30 minutes prior to desired sexual activity, while Viagra should be taken 30 to 60 minutes prior to sexual activity. Unlike Viagra, Cialis can also be taken for daily use, allowing patients to have sex spontaneously. Cialis also stays in the bloodstream for longer than Viagra - 36 hours as opposed to 4 hours - so which medication your doctor prescribes may depend on certain medical conditions that could cause side effects with the medication.

Effectiveness

The perceived effectiveness of Cialis and Viagra depends on your personal needs. Cialis is considered the “endurance athlete” between the two medications, as it can be taken 30 minutes before sex and lasting up to 36 hours when taken as needed.  Viagra can be taken 30 to 60 minutes before sex and lasts for up to 4 hours, which is helpful for those who take medications that would interfere with the drug if it remained in the bloodstream. The effectiveness of Viagra has been heavily studied, since it was the first erectile dysfunction medication approved in the United States. Studies found that approximately 4 out of 5 men taking Viagra at dosages of 50 mg or 100 mg were successfully able to get and keep erections hard enough for sex. Rates of effectiveness generally increased at higher doses.

Risks

Cialis and Viagra are both considered generally safe medications, but they are not appropriate for all individuals. People with the following medical conditions should not take Cialis: 

  • Heart rhythm problems, angina, or any kind of heart disease
  • High or low blood pressure
  • Congestive heart failure or stroke within the last six months, or myocardial infarction within the last three months
  • Sickle cell anemia, multiple myeloma, hemophilia, leukemia, or another blood disorder
  • Liver or kidney disease
  • Stomach ulcer
  • Retinitis pigmentosa
  • Structural deformity of the penis, such as Peyronie’s disease
  • Any health condition for which they have been advised not to have sexual intercourse

There are some people for whom Viagra is not a safe choice of medication. People taking medications called nitrates, which are often prescribed for chest pain, or guanylate cyclase stimulators such as Adempas (riociuguat) for pulmonary hypertension, could experience an unsafe drop in blood pressure if taking Viagra as there are drug interactions. Additionally, people who are allergic to Viagra or any of its inactive or active ingredients should not take the medication. Rare but serious side effects such as heart attack, stroke, irregular heartbeat, and death have occurred in men taking Viagra. Although most of the patients experiencing these side effects had a history of previous heart problems, some patients without a history of heart issues also suffered these effects. It is unknown whether sildenafil causes or contributes to the possibility of experiencing heart attack, stroke, irregular heartbeat, and death, but men with an existing history of heart issues should talk to their doctors about their medical history prior to taking Viagra. 

Side Effects

Cialis

Like any medication, there are side effects associated with the use of Cialis and its generic forms. Common side effects of Cialis are:

  • Indigestion
  • Difficulty falling asleep or staying asleep
  • Back pain
  • Pain in the limbs
  • Muscle aches
  • Nasal congestion or stuffy nose
  • Headache
  • Upset stomach
  • Flushing (feeling of warmth)

Medical attention should be sought immediately if any of the following side effects of Cialis occur during sexual activity:

  • Dizziness
  • Nausea
  • Numbness, tingling, or pain in the jaw, arms, chest, or neck

Other rarely reported, but serious, side effects of Cialis requiring immediate medical attention include:

  • Priapism - erections lasting longer than four hours
  • Sudden vision loss in one or both eyes, which is a symptom of a serious eye problem called non-arteritic anterior ischemic optic neuropathy (NAION)
  • Sudden hearing decrease, hearing loss, or ringing in the ears

Viagra

The side effects most commonly associated with Viagra are similar to those of Cialis and include:

  • Nosebleeds
  • Difficulty falling asleep or staying asleep
  • Numbness, burning, or tingling in the arms, hands, feet, or legs
  • Muscle aches
  • Sensitivity to light
  • Headache
  • Heartburn
  • Diarrhea
  • Flushing (feeling of warmth)

Other rarely reported, but serious, side effects of Viagra requiring immediate medical attention include:

  • Priapism - erections lasting longer than four hours
  • Itching or burning during urination
  • Rash
  • Heart attack
  • Stroke
  • Irregular heartbeat
  • Bleeding in the brain or lungs
  • High blood pressure
  • Sudden vision loss in one or both eyes, which is a symptom of a serious eye problem called non-arteritic anterior ischemic optic neuropathy (NAION)
  • Sudden hearing decrease, hearing loss, or ringing in the ears
  • Dizziness or lightheadedness
  • Fainting
  • Chest pain
  • Worsening shortness of breath
  • Death 
     

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Published May 12th, 2020 by Bridget Reed
Fact Checked by Chris Riley

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