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Should You Pop the Pill?

A Study of the Efficacy of Viagra in Treating Erectile Dysfunction

Cassie Cohen

September 22, 2007

(http://viagra-picture.org/category/viagra-pictures/)
Introduction

You are enjoying a romantic evening with someone special, and things don’t quite work out as planned. Actually, it seems that some things aren’t actually working as planned. You or your partner can’t get or keep and erection firm enough to perform sexual intercourse. If this repeatedly happens on a regular basis, you or your partner may have erectile dysfunction.  Sildenafil citrate (Viagra) is a drug that, when taken an hour before intercourse, claims to improve the response to stimulation, helping achieve an erection. Does Viagra work? How does it work?  Your questions are answered here.

What is Erectile Dysfunction?

            An erection occurs with mental or physical stimulation. The corpora cavernosa, 2 chambers that run along the penis, receive input from the brain (mental stimulation) or surrounding nerves (physical stimulation). This causes the corpora cavernosa to produce nitric oxide, resulting in more cyclic guanosine monophosphate (cGMP), which then causes the arteries to dilate, allowing the blood to flow in (Brain, 2004). Basically, the muscles of the corpora cavernosa relax, which allows blood to enter, causing the penis to become erect. The tunica albuginea, the membrane surrounding the corpora cavernosa helps keep the blood trapped, maintaining the erection until the muscles of the penis contract, stopping the blood flow to the penis and opening the outflow channels, causing the erection to disappear (National Kidney and Urologic Diseases Information Clearinghouse, 2005).

(http://kidney.niddk.nih.gov/kudiseases/pubs/impotence/)

Erectile dysfunction is a failure to get or keep an erection firm enough to have sexual intercourse, which can occur as a result of a range of psychological or physical factors. About 70% of ED cases are caused by certain diseases such as diabetes, alcoholism, multiple sclerosis, atherosclerosis, vascular disease, and kidney disease (NKUDIC, 2005).  Surgery that harms nerves, smooth muscles, arteries, and fibrous tissues of the corpora cavernosa or the penal area are other possible causes of ED (NKUDIC, 2005).  Many common drugs are also known to include ED as a side effect. People who take drugs to reduce blood pressure or suppress appetite should be warned of the risk of ED, as well as those who are taking antihistamines, antidepressants, and tranquilizers (NKUDIC, 2005).   Psychological issues such as performance anxiety, stress, or depression are thought to cause from 10-20% of ED cases.  Lifestyle choices such as being overweight, not exercising, and smoking are also possible causes.  The instance of developing erectile dysfunction also increases with age as a result of the higher risk of related health issues in older men (Sexual Medicine Society of North America Inc., 2007).

What is Viagra, and How Does it Help?

(http://en.wikipedia.org/wiki/Viagra)

Viagra (sildenafil citrate) was the first pill approved to treat erectile dysfunction in the United States. The Food and Drug Administration approved Viagra on March 27, 1998, and since then Viagra’s sales have skyrocketed. Pfizer claims that every second 9 Viagra pills are dispensed, which makes about 300 million pills per year (Brain, 2004)! Levitra (vardenafil hydrochloride) and Cialis (tadalafil) have also been approved by the FDA, and are other popular drugs used to treat ED (NKUDIC, 2005).  All 3 of these approved drugs are phosphodiesterase (PDE) inhibitors.  This means that they enhance the effects of nitric oxide, which is a chemical that creates cGMP that relaxes the muscles in the penis during stimulation, which facilitates the blood to flow into the corpora cavernosa chambers and the penis to become and stay erect (NKUDIC, 2005).  More specifically, Viagra blocks a unique form of the enzyme phosphodiesterase (PDE) in the penis, PDE5. PDE5 decomposes cGMP. Remember that cGMP causes the arteries to dilate in the penis allowing it to be engorged with blood, and become erect. With Viagra blocking the PDE5, cGMP builds up instead of being decomposed, and therefore the arteries are more dilated, more blood flows in, and a stronger erection occurs (Brain, 2004).

Is Viagra Effective?

Carson, Burnett, Levine, & Nehra (2002) used a scientific study to answer this very question.  Carson et al. (2002) evaluated 11 double-blind, placebo-controlled, flexible-dose (meaning the participants took Viagra (sildenafil) as needed) trials in men over 18 years of age, who had been clinically diagnosed with ED at least 6 months beforehand, and who were in a relationship with someone for at least 6 months. Patients were excluded from the study if they had outside contributors to ED such as anatomical defects or other serious sexual disorders that could confound the data.  In total during the 11 double-blind, placebo-controlled trials, 1,329 patients received placebo and 1,338 patients received Viagra (sildenafil), making sure that the relevant patient characteristics were similar in both groups. A range of efficacy measures were used, including the International Index of Erectile Function, where participants answered individual questions and rated them from 0 = no sexual activity to 5 = always/almost always successful. IIEF domain questions were also posed, paying special attention to the answers to the questions about achieving an erection and maintaining an erection. To supplement the questions posed, 6 of the 11 trials had patients keep a log of sexual activity, and using this data Carson et al. (2002) was able to determine the percentage of sexual intercourse attempts that were successful. At the end of treatment, the question “Did treatment improve your erections?” was asked. They studied the efficacy in different patient subgroups characterized by risk factors know to exacerbate ED (like age or the use of antidepressants), factors that could be associated with risk factors (like race), and characteristics associated with the different levels of severity of ED. 

Results concluded that treatment with Viagra (sildenafil) was associated with significantly higher mean scores for the IIEF questions that measured the success rate of getting and keeping an erection than the placebo group. A significant treatment effect was also found across all patient subgroups, whether they were characterized by demographic factors, ED characteristics, varying severity of ED, the duration of ED, or other relevant medical conditions (Carson et al., 2002). After 12 weeks of treating ED with Viagra, 46.5% to 87% of patients indicated that treatment had improved their success with getting and maintaining erections, compared to a much lower 11.3% to 41.3% of patients who received placebos instead of Viagra (Carson et al., 2002). Also, Carson et al. (2002) found that in the 6 trials where the patients kept a log of sexual intercourse attempts, the subgroups who received Viagra as a treatment experienced a 52.6% to 80.1% success rate, as opposed to a success rate of only 14.0% to 34.5% in the placebo subgroups.

Carson et al. (2002) also evaluated the long-term effectiveness of treating ED with Viagra using 3 open-label, flexible-dose studies, totaling 2618 men with ED.  In 2 of the 3 studies, after 12 months of Viagra use, participants were asked “Are you satisfied with the effect that the treatment you have been receiving is having on your erections?” and “If yes, has the treatment improved your ability to engage in sexual activity?” In the other study (N = 979), the use of Viagra was actually extended to 3 years, and after every year efficacy was evaluated by asking the participants the same 2 questions.

Of the participants of the 2 12-month studies from the group of 3 long-term studies, 89% of patients completed the trial year and chose to continue taking Viagra. 95% of these patients who completed the year reported an improvement in their ability to get and maintain erections. Of the 11% of participants who did not complete the year long trial, only “2% discontinued for treatment-related reasons” (Carson et al., 2002).  The other 3 year-long study (N=979) from the group of 3 long-term studies concluded that over 95% of the patients at the end of the 1st, 2nd, and 3rd year of Viagra treatment reported an improved ability to get and maintain an erection, however “over the 3-year period, 32% of patients discontinued treatment” (Carson et al., 2002).  It is important to note that only 6.7% of those who stopped treatment did so for reasons related to the treatment (5.7% reported that Viagra had an insufficient performance and 1% reported that they suffered undesirable treatment-related side effects). The other 25.3% of patients who stopped taking Viagra quit for unrelated reasons. Overall, Carson et al. 2002 concluded that “sildenafil (Viagra) was effective in patients with various comorbid conditions, including diabetes, ischemic heart disease, hypertension, depression, peripheral vascular disease, post-radical prostatectomy, and patients receiving concomitant treatment with antihypertensives or antidepressants. Sildenafil (Viagra) was effective across all efficacy measures, regardless of age, race, BMI, or ED etiology, ED severity, or ED duration.” It would be safe to say that according to this study, Viagra is proven effective.

Literature Cited

 

Brain, Marshall. How Viagra Works. (2004 ). Retrieved September 22, 2007, from http://www.howstuffworks.comviagra.htm

Carson, C., Burnett, A., Levine, L., & Nehra, A. (2002). The efficacy of sildenafil citrate (Viagra) in clinical populations: an update. Urology, 60(2), 12-27. Retrieved September 22, 2007, from ScienceDirect database.

National Kidney and Urologic Diseases Information Clearinghouse. (2005). Erectile               Dysfunction. Retrieved September 22, 2007, from http://kidney.niddk.nih.gov/kudiseases/pubs/impotence/#occur

Sexual Medicine Society of North America Inc. (2007). Erectile Dysfunction-Overview. Retrieved September 22, 2007, from http://sexhealthmatters.org/v2/data/health/ed/overview.asp

Viagra Pictures. (2007). Archive for the ‘Viagra Pictures’ Category. Retrieved September 22, 2007, from http://viagra-picture.org/category/viagra-pictures/

Wikipedia. (2007). Sildenafil. Retrieved September 22, 2007, from http://en.wikipedia.org/wiki/Viagra

 

 

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