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Base information of Product

Introduction of Product

Sildenafil is a white crystalline powder with the molecular formula C22H30N6O4s and a density of 1.39g/cm3. Sildenafil is a drug for erectile dysfunction that was accidentally invented during the development of drugs for cardiovascular diseases. It is commonly known by its trade name Viagra. But Viagra, the generic name for sildenafil in China, is more widely used and influential than its commercial name.

Sildenafil was the first oral anti-impotence drug to be marketed in the United States in April 1998. Many studies have shown that. Nitric oxide (NO) is the main mediator of cavernous smooth muscle relaxation and erection. Sildenafil is a selective inhibitor of phosphodiesterase (PDE) V, which can enhance the physiological response of penile erection caused by NO release during sexual stimulation. The release of NO from nerve endings and endothelial cells binds to receptors on cavernous smooth muscle and activates intracellular soluble guanosine cyclases, which, with the participation of Mn2+, induces the conversion of guanosine triphosphate (GTP) to cyclic guanosine monophophosphate (cGMP), which activates protein kinase G (PKG) and A small portion of protein kinase A (PKA). Activated PKG and PKA reduce intracellular free Ca2+ levels by activating Ca2+ pumps, resulting in relaxation of cavernous smooth muscle, arterial blood inflow, and congestion, stiffness, and erection of the penis. The presence of PDE V in human cavernous tissue and vascular smooth muscle can hydrolyze cGMP to GMP and block the NO-cGMP pathway that causes penile erection. Sildenafil is a selective PDE V inhibitor that prevents the degradation of cGMP and thus enhances the erectile response to sexual excitement. In vitro experiments showed that sildenafil was more selective for PDE V than other PDE isozymes. It has no effect on PDEⅢ, which is involved in heart contraction, but at higher doses it can inhibit PDE in the retina and affect vision. Bottles are imported from the United States and are hard to get at home.

Function and Application of Product

1. Sildenafil is a selective inhibitor of phosphodiesterase (PDE)V, which can enhance the physiological response of penile erection caused by NO release during sexual stimulation. Mainly used for penile erectile dysfunction.

2. In addition to human cavernous smooth muscle, low concentrations of PDE5 were also found in platelets, blood vessels, visceral smooth muscle and skeletal muscle. Sildenafil may enhance antiplatelet aggregation (in vitro), inhibition of platelet thrombosis (in vivo), and peripheral vasodilation by inhibiting PDE5 in these tissues.

The developing history of Sildenafil

Sildenafil be developed by Pfizer, it was first introduced as a 5-phosphodiesterase inhibitor for the treatment of cardiovascular disease. The researchers hope sildenafil will dilate blood vessels and alleviate cardiovascular disease by releasing the biologically active nitric oxide, which relaxes cardiovascular smooth muscle. However, clinical studies have shown that sildenafil is not as effective as expected. As a cardiovascular drug, sildenafil has shown disappointing performance and has not been able to grow into a successful treatment. In April 1991, a clinical trial of sildenafil officially failed, but a side effect reported by subjects caught researchers' attention. The researchers found that patients who had been tested were reluctant to hand over the remaining drugs. When tracked down, the drug was found to improve the patients' sex lives. Sildenafil's effects on the cavernous muscle of the penis were studied with the approval of Pfizer executives, and on March 27, 1998, the FDA approved the product, making it one of Pfizer's best-known products.

Usage and dosage

1. Sildenafil for most patients, the recommended dose is 50mg, to be taken as needed approximately 1h before sexual activity and to be sexually stimulated after taking the drug. However, it can be taken at any time between 0.5 and 4h before sexual activity. Based on efficacy and tolerance, the daily dose can be adjusted between 25 and 100mg, and the drug should not be taken more than once a day. (1) The recommended starting dose for renal insufficiency is 25mg for patients with severe renal insufficiency (AUC and Cmax are nearly doubled when creatinine clearance is less than or equal to 30 mL /min). (2) The recommended starting dose for liver function impairment (e.g., in cirrhosis, AUC and Cmax increase by 84% and 47%, respectively) is 25mg.

2. Elderly Dose The starting dose for people over 65 years of age is recommended to be 25mg.

3. Dose for other diseases (1) The appropriate starting dose for those taking potent cytochrome P4503A4 inhibitor and erythromycin at the same time is 25mg. (2) It is recommended that sildenafil dose not exceed 25mg every 48 hours in patients taking HIV protease inhibitor prickle (such as ritonavir).