The following diagram shows how an erection is mediated and how sildenafil acts in the body. Nitric Oxide (NO) is released with sexual stimulation from nerve endings and endothelial cells in the spongy erectile tissue, the corpus cavernosum of the penis. The enzyme guanylate cyclase then converts guanosine triphosphate (GTP) into cyclic guanosine monophosphate (c GMP). c GMP causes the smooth muscle to relax, which causes an inflow of blood which then leads to an erection. c GMP is then hydrolysed back to the inactive GMP by phosphodiesteras type 5 (PDE5). The levels of c GMP are therefore controlled by the activation of cyclic nucleotide cyclase and the breakdown by PDE5. Men who suffer from erectile dysfunction often produce too little amounts of NO. This means that the small amount of c GMP they produce is broken down at the same rate and therefore doesn't have the time to accumulate and cause a prolonged vasodilation effect. 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).
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 continuous sexual excitement the user will reach orgasm after 4 hours? Or is it that the user reaches his regular orgasm in 15 minutes but the erection still remains? Please indicate for a normal guy for the erection to last for 30 about minutes, will 25 mg be enough? A: Kindly note the following points:(a) In India, the brand name of Sildenafil is Penegra and not Viagra.(b) Sildenafil has an anatomic role and helps in erection. In fact if there is no desire, sildenafil will not act.(c) Normally the erection will be considerably decreased after ejaculation. Reference to 4 hours is to indicate maximum duration of action of the drug. This was the first of a group of drugs called phosphodieterase inhibitors or PD5 inhibitors for short. They work by allowing an increase of blood into the penis and maintaining the erection for longer. It’s a bit like filling a bath – if you turn the taps on full the bath will fill, even though the plug is out. Other drugs like Cialis and Levitra are variations on the same theme but with their own characteristics. low sex drive, lack of morning erections, less intensity during ejaculation, less hard erections, irritability, etc.. I had my doctor run blood tests and everything came back normal. Doctor says this is normal and will not consider hormone treatments. The only medication I take is a statin, which has lowered my cholestorol to normal levels. Hi I m a 28 year old and suffer some degree of ED in recent.
Mode of Action. Filling the penis with blood occurs by delivering blood through blood vessels, which leads to an increase in the size of penis and itsIt should be remembered that sildenafil citrate must not be used simultaneously with grapefruit, as this leads to an overdose of the main substance. 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.