Erectile dysfunction drugs have become a billion dollar industry. Commercials appear on almost every televised sporting event, and men’s magazines are filled with ads to “increase your sexual performance”. Almost everyone is familiar with Viagra, “the little blue pill”. It has been endorsed by celebrities such as NASCAR star Mark Martin, baseball all-star Rafael Palmeiro, and even former Republican presidential candidate Bob Dole. Cialis, another of the dominant erectile dysfunction drugs, has also become a household word. The image of a man and a woman relaxing in separate bathtubs has become as universally recognized as the McDonalds golden arches.
But is there a difference between the erectile dysfunction drugs? Is one safer? More effective? There is no simple answer to these questions. People aren’t all alike, and the treatment that is successful for one man might not be ideal for another. However, it is certainly worthwhile to review the characteristics of each drug. With this knowledge, you and your health care provider should be able to make an informed decision about which drug is right for you.
Mechanism of Action
Viagra (sildenafil) and Cialis (tadalafil) work in a very similar fashion. Both drugs increase the flow of blood into the penis so that when a man is sexually stimulated, he can get and maintain an erection. Viagra and Cialis belong to a class of drugs known as PDE5 inhibitors, which enhance the effect of nitric oxide, a chemical that is normally released during stimulation. Nitric oxide opens and relaxes blood vessels in the penis, thereby increasing inflow and allowing erections to last longer.
It is important to realize that neither drug is an aphrodisiac. You must feel sexually aroused in order for them to cause erections.
Viagra is typically prescribed in a dosage of 50 mg, taken as needed approximately 1 hour before sexual activity. Based on effectiveness and toleration, the dose may be increased to a maximum dose of 100 mg or decreased to 25 mg. In most patients, the maximum recommended dosing frequency is once per day. Viagra is best taken on an empty stomach, since its action may be delayed or impaired when taken with food (especially high-fat foods).
Cialis is typically prescribed in a dosage of 10 mg, taken as needed approximately 45 minutes before sexual activity. Based on effectiveness and toleration, the dose may be increased to a maximum dose of 20 mg or decreased to 5 mg. In most patients, the maximum recommended dosing frequency is once per day. Cialis can be taken with or without food.
A low-dose version of Cialis for daily use is also available. The recommended starting dose of Cialis for daily use is 2.5 mg, taken at approximately the same time each day.
Viagra and Cialis have both been shown to be effective in 60-70% of men with erectile dysfunction. Because Viagra has been available the longest (since 1998), there is much more research available. There are also more positive testimonials from consumers. But Cialis (which entered the market 5 years later) seems to have a very similar efficacy profile. The least amount of data is available on the low-dose version of Cialis, although one small study showed that efficacy varied greatly depending on the level of erectile dysfunction (73%-82% efficacy in patients with mild erectile dysfunction, 56%-61% efficacy in men with moderate erectile dysfunction, and 27%-33% efficacy in men with severe erectile dysfunction).
There are very few published head-to-head studies comparing Viagra and Cialis. Most studies have compared the drugs to placebo. In addition, it is difficult to make comparisons across studies, since different studies use different measures of efficacy (e.g. improvement in sexual function versus improvement in sexual satisfaction).
Duration of Effectiveness
The main difference between Viagra and Cialis has to do with duration of effectiveness. Viagra lasts about four to five hours, but with Cialis, the window of opportunity ranges from 24 to 36 hours, which is why it is sometimes called “the weekend drug.” For couples who prize sexual spontaneity, Cialis seems to have a clear competitive edge in this category.
With the low-dose version of Cialis for daily use, there is a steady supply of the drug in the bloodstream. Theoretically, this option makes having sex a possibility without any advance planning at all.
Viagra and Cialis have similar side effects. The most common side effect is a headache, which occurs in about 16% of patients. Other common side effects include nasal congestion, facial flushing, stomach ache, and urinary tract infections. Back pain and muscle aches may occur with Cialis, but rarely with Viagra. In some cases, men taking Viagra and Cialis experience temporary vision problems – mainly a blue tinge to the vision or difficulty in distinguishing the colors blue and green. An extremely rare but very serious side effect associated with both Viagra and Cialis is priapism, an abnormally long and painful erection. If not treated promptly, priapism can lead to erectile dysfunction.
When the drugs are used properly, their side effects tend to be relatively mild. Most disappear after a few hours. However, since Cialis has a longer duration of effectiveness, its side effects tend to last longer, which some men find troubling.
Viagra and Cialis should not be taken by men who take medicines or recreational drugs containing nitrates. Like Viagra and Cialis, nitrate drugs cause blood vessels to dilate. The combined effects could cause a dramatic drop in blood pressure, resulting in dizziness, fainting, and sometimes loss of consciousness. Nitrate medicines include nitroglycerin and isosorbide (both used to treat the chest pain associated with angina). Nitrates are also contained in street drugs called “poppers” and in some air fresheners which are inhaled to enhance sexual pleasure.
Cialis should not be taken by men who are on medicines called alpha blockers which are sometimes used to treat prostate problems or high blood pressure. Men who take alpha blockers can use Viagra but must allow at least a six hour gap between taking the alpha blocker and Viagra.
Men taking Cialis may experience an unsafe drop in blood pressure if they drink too much alcohol. The same is true for Viagra, but since Viagra is shorter-acting, this may be less of an issue.
Men who have had a heart attack or stroke within the past 6 months and those with certain medical conditions (e.g., poorly controlled high or low blood pressure, poorly controlled diabetes, liver disease, and unstable angina) that make sexual activity inadvisable should not take Viagra or Cialis. Dosages of the drug should be limited in patients with kidney or liver disorders.
Viagra and Cialis have many more similarities than differences. Both drugs appear to be safe and effective. Cialis lasts longer, allowing greater sexual spontaneity, and can be taken with food. However, the side effects of Cialis can be prolonged and there can be an increased risk for drug interactions. In many cases, insurance coverage and cost may be the deciding factors.
If you are suffering from erectile dysfunction, a complete physical examination by your doctor or healthcare provider is essential. In some cases, erectile dysfunction may be a sign of an underlying medical condition. Your doctor can determine if any other conditions are involved and help you choose the best and safest therapy.
3) The PDE5 inhibitors: Viagra, Levitra, and Cialis
Source: Patient Education Center, Harvard Medical School
4) Erectile dysfunction: Viagra and other oral medications
Source: Mayo Clinic
5) Comparison of Viagra, Levitra, and Cialis
Source: eMed Expert