A Comprehensive Look On Erectile Dysfunction
Erectile dysfunction as well as cardiovascular disease is one of the most common diseases of modern civilization. According to the classic Massachusetts study, 52% of men aged 40 to 69 years old suffer from ED, and in 5-15% of these males ED is characterized by complicated course of action and moderate in another 25%. This study also clearly demonstrates that with age not only increases the incidence of erectile dysfunction (from 39% in 40 years to 67% in 70 years), but also exacerbates the degree of its severity.
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It is also clear that erectile function is a key parameter that determines the quality of life in men. That is why during the last decades the diagnosis and treatment of ED was an area of increased attention. Thus, over the past 20 years, experts have radically revised the outlook on the etiology of ED: it was found that 80% of patients suffered from erectile dysfunction due to organic causes (disorders of blood circulation and innervation of the corpora cavernosa of the penis), not mental factors, as previously considered.
In addition to the realization of the organic nature of the overwhelming majority of ED cases, a revolutionary breakthrough in medical treatment emerged almost simultaneously: since 1998 an inhibitor of phosphodiesterase type 5 (PDE5), sildenafil, has been used in clinical practice. Thus, emerged a new class of oral agents, which quickly gained the position of first-line ED treatment. In many ways, the emergence of this high quality remedy contributed to the transition of the professional term impotence, having a tinge of despair, to the term erectile dysfunction, which implied a "correctable problem".
Among PDE5 inhibitors, sildenafil is considered to be the most studied and proven by today. Thus, by the beginning of April 2014 the database of clinical trials noted 428 studies of sildenafil, 124 tadalafil studies, 78 vardenafil studies, 29 udenafil studies and 20 avanafil studies. It is also important that in large multicenter studies high efficacy and safety of sildenafil has been established not only in the general population of patients with erectile dysfunction, but also in patients with ED with hypertension, coronary heart disease, diabetes, hyperlipidemia, after prostatectomy, depression, scattered sclerosis, spinal cord injury and those on hemodialysis. None of PDE5 inhibitors can boast such a deep degree of investigation. Moreover, it could claim that the spectrum of patients, observed and treated in clinical trials, fully reflects the diversity of patients in routine clinical practice.
PDE5 duration of action
The duration of action in PDE-5 inhibitors is different: 4 hours in sildenafil, 8-12 hours in vardenafil, 24 hours in udenafil and 48 hours in tadalafil. Which one can be considered to be optimal? This question was answered by the results of the survey conducted in 2010 among patients suffering from ED. It turned out that 97% of men go to the sexual contact no more than 4 hours after ingestion. Thus, from the point of view of the needs of most patients, the optimal duration of action is offered by sildenafil. Do not forget that in the event of adverse events (AEs) the effect depends on the duration of drug action. Thus, according to Taylor et al., the effect after administration of sildenafil is maintained during an average of 3.9 hours, vardenafil provides an average of 7.7 hours of effect, while tadalafil provides an average of 14.9 hours.
The efficiency of sildenafil therapy deserves special attention, since in comparison with other PDE5 inhibitors due the increased severity of the primary clinical effect. It is noteworthy that almost simultaneously with the appearance of sildenafil, a number of important tools (for example, International Index of Erectile Function (IIEF)) in order to accurately assess the effectiveness of treatment of patients with ED was introduced in routine clinical practice. In 2007, the International Council of experts for ED recommended using erection hardness scale as a key tool for evaluating the effectiveness of treatment of ED along with the already used IIEF questionnaire.
From the viewpoint of safety of use and side effect profile, a very important property of PDE5 inhibitors is their selectivity for other PDE subtypes. Given that a key objective of the treatment of patients with ED is to improve their quality of life, even a minor degree of severity and a risk to the health posed by side effects can be a serious obstacle to the continuation of treatment. In the meta-analysis of Moore et al. 2002, it was demonstrated that when taken in a dosage of 100 mg of even such a well-balanced drug in its properties as sildenafil, 50% of patients still have the certain side effects (headache, facial flushing, changes in color vision, etc.). In this same study, it was shown that the selection of individual minimum effective dose of sildenafil reduces side effects by 41% while maintaining efficiency.
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