Sildenafil CAS 139755-83-2 Viagra

Sildenafil CAS 139755-83-2 Viagra

Sildenafil CAS 139755-83-2 Viagra, raw powder in stock. Hot sell in USA, Europe and Australia.

CAS 139755-83-2 Basic Parameter

Sildenafil Packing Picture

What is Sildenafil?

Sildenafil, sold under the brand name Viagra, among others, is a medication used to treat erectile dysfunction and pulmonary arterial hypertension. It is also sometimes used off-label for the treatment of certain symptoms in secondary Raynaud’s phenomenon. It is unclear if it is effective for treating sexual dysfunction in females. It can be taken orally (swallowed by mouth), intravenously (injection into a vein), or through the sublingual route (dissolved under the tongue). Onset when taken orally is typically within twenty minutes and lasts for about two hours.

Usage:

Medical uses

Sexual dysfunction 

The primary indication of Viagra is treatment of erectile dysfunction (inability to sustain a satisfactory erection to complete sexual intercourse). Its use is now one of the standard treatments for erectile dysfunction, including for males with diabetes mellitus.

Antidepressant-associated sexual dysfunction

Tentative evidence suggests that sildenafil may help males who experience antidepressant-induced erectile dysfunction.

Pulmonary hypertension 

While Viagra improves some markers of disease in people with pulmonary arterial hypertension, it does not appear to affect the risk of death or serious side effects.

Raynaud’s phenomenon

Sildenafil and other PDE5 inhibitors are used off-label to alleviate vasospasm and treat severe ischemia and ulcers in fingers and toes for people with secondary Raynaud’s phenomenon; these drugs have moderate efficacy for reducing the frequency and duration of vasospastic episodes. As of 2016, their role more generally in Raynaud’s was not clear.

High-altitude pulmonary edema

Viagra has been studied for high-altitude pulmonary edema, but its use is currently not recommended for that indication.

Mechanism of action

Sildenafil protects cyclic guanosine monophosphate (cGMP) from degradation by cGMP-specific phosphodiesterase type 5 (PDE5) in the corpus cavernosum. Nitric oxide (NO) in the corpus cavernosum of the penis binds to guanylate cyclase receptors, which results in increased levels of cGMP, leading to smooth muscle relaxation (vasodilation) of the intimal cushions of the helicine arteries. This smooth muscle relaxation leads to vasodilation and increased inflow of blood into the spongy tissue of the penis, causing an erection. Robert F. Furchgott, Ferid Murad, and Louis Ignarro won the Nobel Prize in Physiology or Medicine in 1998 for their independent study of the metabolic pathway of nitric oxide in smooth muscle vasodilation.

The molecular mechanism of smooth muscle relaxation involves the enzyme CGMP-dependent protein kinase, also known as PKG. This kinase is activated by cGMP and it phosphorylates multiple targets in the smooth muscle cells, namely myosin light chain phosphatase, RhoA, IP3 receptor, phospholipase C, and others. Overall, this results in a decrease in intracellular calcium and desensitizing proteins to the effects of calcium, engendering smooth muscle relaxation.

Sildenafil is a potent and selective inhibitor of cGMP-specific phosphodiesterase type 5 (PDE5), which is responsible for degradation of cGMP in the corpus cavernosum. The molecular structure of sildenafil is similar to that of cGMP and acts as a competitive binding agent of PDE5 in the corpus cavernosum, resulting in more cGMP and increased penile response to sexual stimulation. Without sexual stimulation, and therefore lack of activation of the NO/cGMP system, sildenafil should not cause an erection. Other drugs that operate by the same mechanism include tadalafil (Cialis) and vardenafil (Levitra).

Viagra is broken down in the liver by hepatic metabolism using cytochrome p450 enzymes, mainly CYP450 3A4 (major route), but also by CYP2C9 (minor route) hepatic isoenzymes. The major product of metabolisation by these enzymes is N-desmethylated sildenafil, which is metabolised further. This metabolite also has an affinity for the PDE receptors, about 40% of that of sildenafil. Thus, the metabolite is responsible for about 20% of sildenafil’s action. Sildenafil is excreted as metabolites predominantly in the feces (about 80% of administered oral dose) and to a lesser extent in the urine (around 13% of the administered oral dose). If taken with a high-fat meal, absorption is reduced; the time taken to reach the maximum plasma concentration increases by around one hour, and the maximum concentration itself is decreased by nearly one-third.

Chemical synthesis 

The preparation steps for synthesis of sildenafil are:

1. Methylation of 3-propylpyrazole-5-carboxylic acid ethyl ester with hot dimethyl sulfate
2. Hydrolysis with aqueous sodium hydroxide (NaOH) to free acid
3. Nitration with oleum/fuming nitric acid
4. Carboxamide formation with refluxing thionyl chloride/NH₄OH
5. Reduction of nitro group to amino group
6. Acylation with 2-ethoxybenzoyl chloride
7. Cyclization
8. Sulfonation to the chlorosulfonyl derivative
9. Condensation with 1-methylpiperazine.

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