VIAGRA (sildenafil citrate) is a c GMP-specific phosphodiesterase type 5 (PDE5) inhibitor, used for the treatment of male erectile dysfunction. The physiological mechanism responsible for erection of the penis involves the release of nitric oxide (NO) in the in response to sexual stimulation. Nitric oxide then activates the enzyme guanylate cyclase, which results in increased levels of cyclic guanosine monophosphate (c GMP), producing smooth muscle relaxation in the have shown that sildenafil has between 10 and 10,000-fold greater selectivity for PDE5 than for other phosphodiesterase isoforms namely PDEs 1, 2, 3, 4, and 6 and greater than 700-fold effect on PDE7-PDE11. In particular, sildenafil has greater than 4,000-fold selectivity for PDE5 over PDE3, the c AMP-specific phosphodiesterase isoform involved in the control of cardiac contractility. Sildenafil is about 10-fold as potent for PDE5 compared to PDE6, an isoenzyme found in the retina; this lower selectivity is thought to be the basis for colour vision abnormalities observed with higher doses or plasma levels of sildenafil (see WARNINGS AND PRECAUTIONS, DETAILED PHARMACOLOGY). PDE5 is also found in lower concentrations in platelets, vascular and visceral smooth muscles, and skeletal muscle. The sildenafil-induced inhibition of PDE5 in these tissues appears to be the basis for the enhanced platelet antiaggregatory activity of nitric oxide observed (see WARNINGS AND PRECAUTIONS). buy viagra in mexico city The primary indication of sildenafil is treatment of erectile dysfunction (inability to sustain a satisfactory erection to complete intercourse). Its use is now one of the standard treatments for erectile dysfunction, including for men with diabetes mellitus. Rare but serious adverse effects found through postmarketing surveillance include prolonged erections, severe low blood pressure, myocardial infarction (heart attack), ventricular arrhythmias, stroke, increased intraocular pressure, and sudden hearing loss. Care should be exercised by people who are also taking protease inhibitors for the treatment of HIV infection. Protease inhibitors inhibit the metabolism of sildenafil, effectively multiplying the plasma levels of sildenafil, increasing the incidence and severity of side effects. Those using protease inhibitors are recommended to limit their use of sildenafil to no more than one 25 mg dose every 48 hours. blocker (typically prescribed for hypertension or for urologic conditions, such as benign prostatic hypertrophy) at the same time may lead to low blood pressure, but this effect does not occur if they are taken at least 4 hours apart. Accutane where can i buy it Metformin pi Sildenafil vs sildenafil citrate Action And Clinical Pharmacology. Mechanism of Action. VIAGRA sildenafil citrate is a cGMP-specific phosphodiesterase type 5 PDE5 inhibitor, used for the. propranolol 10 mg anxiety The article on Sildenafil on your site says that if one consumes Sildenafil Viagra, he may have an erection upto 4 hours. Does this mean that given there is. Sildenafil Mode Of Action Save up to 80% when buying prescription drugs online. PlanetDrugsDirect has served over 100000 customers in the US. Use our prescription. If you said no, then you've definitely heard of Viagra, the brand name for the generic term of sildenafil. Viagra is used to treat erectile dysfunction (impotence). Another brand name version of sildenafil, Revatio, is used to manage pulmonary arterial hypertension (PAH), or high blood pressure (hypertension) in the arteries of the lungs ('pulmon-'). You can check out the structure of sildenafil in this lesson's image. And if you keep reading, you'll also learn exactly how it is that sildenafil works at treating both of these conditions. An erection occurs and disappears as a result of an interplay of forces. Not to be funny, just for simplicity's sake, we'll call the forces that lead to an erection as the good guys and the ones that cause one to disappear as the bad guys. Sildenafil is a vasoactive agent used to treat erectile dysfunction and reduce symptoms in patients with pulmonary arterial hypertension (PAH). Sildenafil elevates levels of the second messenger, c GMP, by inhibiting its breakdown via phosphodiesterase type 5 (PDE5). PDE5 is found in particularly high concentrations in the corpus cavernosum, erectile tissue of the penis. It is also found in the retina and vascular endothelium. Increased c GMP results in vasodilation which facilitates generation and maintenance of an erection. The vasodilatory effects of sildenafil also help reduce symptoms of PAH. 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