A modern view on the use of sildenafil citrate

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Erectile dysfunction (ED) is characterized by a persistent inability to achieve or maintain an erection sufficient for successful sexual intercourse. This erection disorder is widespread and by 2025 it is estimated to affect 322 million men worldwide. What role does sildenafil citrate play and how to solve the ED problem?

The data of the last separate study on the prevalence of ED in the USA based on the analysis of the survey data of 1,225 respondents showed the following: When analyzing the ICEF-5 questionnaire, it was revealed that only 10% of the men surveyed had no signs of ED, while a mild degree of ED was noted in 71%, an average degree in 6% and a severe degree in 12% of respondents. Thus, out of 1225 men surveyed, 1101 (89.9%) respondents had symptoms of ED.

For many decades, ED treatment has been carried out by specialists who did not have sufficient knowledge about the pathophysiology and mechanisms of erection. So, in 1668 intracavernous injections of salt solutions were performed for the first time, then numerous variants of oral therapy with various tinctures (for example, from animal testicles) were used, subcutaneous injections of ejaculate were proposed in the 19th century, the first penile implantation was performed in 1936.

Currently, the polyethological nature of the disease is taken into account in the treatment of ED, but the first line of therapy, despite all the variety of causes of ED, are phosphodiesterase type 5 inhibitors (IFDE-5). The noninvasiveness of iFDE-5 therapy has increased the availability of treatment compared to other therapeutic methods, which include intracavernous injections of vasoactive drugs, vacuum devices, penile prostheses and surgical vascular reconstructions.

Sildenafil citrate: type 5 inhibitors

The history of the use of iFDE-5 began in March 1998, when the drug sildenafil was approved for use by the Food and Drug Administration (FDA) in the United States of America. With the appearance on the market of this first effective tablet drug for the treatment of ED, sildenafil has rightfully become the flagship and gold standard of the first line of ED therapy. Vardenafil and tadalafil, which were introduced somewhat later, are also known as selective inhibitors of iFDE-5. Thus, sildenafil (viagra) is the most studied drug in terms of safety and efficacy among iFDE-5.

Sildenafil citrate provides an increase in the concentration of cyclic guazine monophosphate (cGMP) in the smooth muscle cells of the cavernous body of the penis, which, in turn, leads to an increase in the level of nitric oxide (NO) in these cells and, as a consequence, to relaxation of these cells and increased blood flow in the penis. When the NO-cGMP chain is activated, observed during sexual arousal, PDE5 inhibition leads to an increase in cGMP in the cavernous body. The pharmacological effect is achieved only in the presence of sexual stimulation.

The use of sildenafil in patients with cardiovascular diseases

In the American Massachusetts Male Aging Study, the incidence of ED in men aged 40-70 years was 52%. In the German study Cologne Male Survey, when analyzing the population, the frequency of ED was 10% in men aged 40-49 years, 16% – aged 50-59 years, 34% – aged 60-69 years and more than 50% – aged 70 to 80 years. Thus, the main group of patients with erectile dysfunction are men over 50 years old, at this age the frequency of cardiovascular diseases, including myocardial infarction and stroke, increases. Sexual dysfunction in men with cardiovascular diseases is a common phenomenon. Many patients stop having sex because of the fear that physical efforts during sexual activity will be complicated by repeated myocardial infarction. However, there are a number of studies proving the safety and effectiveness of the use of sildenafil citrate in a group of patients with ED and cardiovascular diseases.

sildenafil citrate

In a phase II/III double-blind open-label study conducted by the FDA, more than 3,700 ED patients received sildenafil and almost 2,000 received placebo. Approximately 25% of patients suffered from arterial hypertension and took antihypertensive drugs, 17% had diabetes. In these studies, the incidence of serious cardiovascular complications was the same in the sildenafil and placebo groups. 28 patients who had suffered a myocardial infarction during the study were registered. The incidence of myocardial infarction was 1.7% in the sildenafil group and 1.4% in the placebo group. There were no differences in the rate of occurrence of cardiovascular diseases between the two groups, and no deaths were associated with treatment. Histomorphological studies did not find any traces of iFDE-5 in the necrosis zone and ventricular tissue of the heart, but traces of iFDE-5 were found in the atria.

In the studies of M. Guazzi et al. it was revealed that sildenafil improves the condition of the endothelium. The authors noted dependent flow-mediated dilatation of the brachial artery in patients with heart failure and type 2 diabetes mellitus.

In patients with heart failure due to ischemic or non-ischemic heart disease without lung disease, a single dose of 50 mg of sildenafil caused a significant increase in the cardiac index and a decrease in pulmonary vascular resistance both at rest and during exercise. In patients with coronary artery diseases, the positive effect of sildenafil on skin microcirculation has been established.

The vasodilating effect of sildenafil affects both arteries and veins, so the most common side effects are headache and facial hyperemia. Sildenafil causes a slight decrease in systolic and diastolic blood pressure, but clinically significant hypotension is rarely observed, at the same time, the combined intake of sildenafil and nitrates causes a more significant drop in blood pressure. For this reason, sildenafil is contraindicated for use in patients within a day after taking short-acting nitrates. Meanwhile, about 5.5 million men need constant intake of nitrates, which leaves the question of further research on the joint intake of these substances open.

The use of sildenafil citrate in patients with diabetes mellitus

In the practice of a therapist, the use of sildenafil in diabetes mellitus is an urgent issue, since in patients suffering from type 1 and type 2 diabetes, erectile dysfunction occurs three times more often than in the general patient population. Moreover, erectile dysfunction can be considered as an early marker of diabetes mellitus. Thus, 12% of men suffering from erectile dysfunction were diagnosed with diabetes mellitus for the first time during the examination. Another 50% are expected to develop ED within 5-10 years after diagnosis.

The mechanism of ED in men with diabetes mellitus is mainly caused by organic factors: vasculogenic and neurological. Goldstein in a study of the use of sildenafil citrate at a dosage of 50 mg in patients with diabetes mellitus reported a 52% improvement in erectile function compared with the placebo group. Similar data were obtained by M.S. Rendell, they noted an improvement in erectile function in 56% of patients taking sildenafil at a dosage of 100 mg versus 10% in the placebo group. Thus, sildenafil is effective and well tolerated in the treatment of organic ED in men with diabetes mellitus.

Sildenafil citrate in psychotherapeutic practice

Erectile dysfunction is a polyetiological disease and in some cases may be caused by various psychogenic factors that require specialized therapy. ED can both cause depression and be its consequence.

It was noted that with antidepressant monotherapy, antidepressant-induced ED occurs in 37% of cases, manifested by a decrease in libido, difficult ejaculation and anorgasmia. In a 12-week randomized, double-blind, placebo-controlled study based on 20 urological clinics, the effect of sildenafil on erectile dysfunction in men with mild to moderate depressive disorders was evaluated. Sildenafil not only proved to be an effective drug for the treatment of erectile dysfunction, but also caused a noticeable reduction in symptoms of depression and improved quality of life: 60 (90.9%) of 66 men taking sildenafil reported that treatment improved erection and 59 (89.4%) noted an improvement in the ability to perform sexual intercourse, compared with 8 (11.4%) and 9 (12.9%) of 70 men receiving placebo, respectively.

A meta-analysis of 9 randomized trials involving 398 men with ED of mixed etiology, who underwent various treatments: 141 patients used only psychotherapy, 109 – only sildenafil, 68 – psychotherapy with sildenafil, 20 people used vacuum devices and 59 people were included in the control group. The best indicators of successful treatment were obtained for a group of patients in which psychotherapeutic treatment was combined with sildenafil.

In another study, the effect of sildenafil on the mental health of a married couple was assessed using a Self-Esteem And Relationship questionnaire (SEAR). According to the results of the questionnaire, after a year of taking the drug, such indicators as: general well-being, self-control, satisfaction in relationships significantly increased. The authors recommend taking the drug to improve the overall mental health of not only men, but also couples in general.

Individual issues of the use of sildenafil

Prostate cancer and ED

Treatment of erectile dysfunction with sildenafil in patients undergoing radiation therapy for prostate cancer (prostate cancer) initially showed its effectiveness in uncontrolled studies, and then confirmed in a controlled study. 50 patients with ED after radiation therapy of localized prostate cancer took 50 mg of sildenafil. At the same time, 66-74% of the patient noted a significant improvement in erection.

The most significant prognostic factors for the restoration of erectile function after radical prostatectomy are the bilateral preservation of neurovascular bundles and the absence of erectile disorders before surgical treatment. According to M.Tutolo et al., the effectiveness of sildenafil for the treatment of ED in 170 men after radical nerve-sparing prostatectomy was 80%. In a randomized, double-blind, placebo-controlled study, H. Padma-Nathan et al. It is reported that the early administration of iFDE-5 increases the recovery of spontaneous erections, and the effectiveness of sildenafil increases with time, and the best results are observed 12-24 months after surgery.

Pelvic injury and ED

Pelvic and perineal injuries can cause erectile dysfunction. P.J. Harwood et al. It was noted that as a result of a fracture of the pelvic bones and damage to the urethra, 30% and 42% of patients, respectively, had erectile dysfunction. O.Z. Shenfield et al. It was reported that after urethroplasty, the administration of sildenafil at a dosage of 100 mg significantly reduced the manifestation of ED in 47% of patients. It is noted that the drug is most effective for injuries of the genitourinary organs with preserved innervation and blood supply.

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