Buy Levitra 20mg online

Tablets coated with a blue color, diamond-shaped, slightly biconvex, with cut and rounded edges, with the inscription "Pfizer" on one side and "VGR 25" on the other. 1 tab. sildenafil (in the form of citrate) 25 mg. Excipients: microcrystalline cellulose, anhydrous calcium hydrophosphate, sodium croscarmellose, magnesium stearate, Opadry blue and Opadry transparent film coating.
Tablets coated with a blue color, diamond-shaped, slightly biconvex, with cut and rounded edges, with the inscription "Pfizer" on one side and "VGR 50" on the other. 1 tab. sildenafil (in the form of citrate) 50 mg. Excipients: microcrystalline cellulose, anhydrous calcium hydrophosphate, sodium croscarmellose, magnesium stearate, Opadry blue and Opadry transparent film coating.
Tablets coated with a blue color, diamond-shaped, slightly biconvex, with cut and rounded edges, with the inscription "Pfizer" on one side and "VGR 100" on the other. 1 tab. sildenafil (in the form of citrate) 100 mg. Excipients: microcrystalline cellulose, anhydrous calcium hydrophosphate, sodium croscarmellose, magnesium stearate, Opadry blue and Opadry transparent film coating.

Clinical and pharmacological group: A drug used for erectile dysfunction.

Pharmacological action

A drug for the treatment of erectile dysfunction. Sildenafil is a potent selective inhibitor of cGMP-specific phosphodiesterase type 5 (PDE5). Sildenafil does not have a direct relaxing effect on the isolated cavernous body, but enhances the relaxing effect of NO on this tissue by inhibiting PDE5, which is responsible for the breakdown of cGMP in the cavernous body.
Inhibition of PDE5 under the influence of sildenafil leads to an increase in the level of cGMP in the cavernous body, resulting in relaxation of smooth muscles and increased blood flow in the cavernous body. The use of Levitra 20mg in the recommended doses is ineffective in the absence of sexual stimulation. Sildenafil is selective against PDE5 in vitro, its activity against PDE5 exceeds the activity against other known phosphodiesterase isoforms (10 times – PDE6, more than 80 times – PDE1, more than 700 times - PDE2, PDE4, PDE7 – PDE11).
Levitra 20mg is approximately 4000 times more active against PDE5 than against PDE3–cAMP-specific phosphodiesterase involved in myocardial contraction. In some patients, 1 hour after taking the drug at a dose of 100 mg using the Farnsworth-Munsell 100 test, a slight and transient impairment of the ability to distinguish shades of color (blue / green) was detected; 2 hours after taking the drug, these changes were absent.
It is believed that color vision impairment is caused by inhibition of PDE6, which is involved in the process of light transmission in the retina. Levitra  has no effect on visual acuity, contrast perception, electroretinogram, intraocular pressure or pupil diameter.

Pharmacokinetics

The pharmacokinetics of sildenafil depends on the dose when taken orally in the recommended dose range.

Suction

After taking the drug inside, sildenafil is rapidly absorbed. Absolute bioavailability averages 40% (25-63%). In vitro, sildenafil at a concentration of approximately 1.7 ng/ml (3.5 nM) suppresses human PDE5 by 50%. After a single dose of 100 mg of the drug inside, Cmax is 18 ng / ml (38nM) and is achieved when taken on an empty stomach for 30-120 minutes (on average 60 minutes).
When taking Levitra  in combination with fatty foods, the absorption rate decreases; Tmax increases by 60 minutes, and Cmax decreases by an average of 29%.
The distribution of Vd of Levitra  in the equilibrium state is on average 105 liters. Levitra  and its main circulating N-desmethyl metabolite bind approximately 96% to plasma proteins. Protein binding does not depend on the total concentration of sildenafil. Less than 0.0002% of the dose (on average 188 ng) was detected in semen 90 minutes after taking levitra.

Metabolism

Levitra is metabolized mainly in the liver under the action of microsomal isoenzymes CYP3A4 (the main pathway) and CYP2C9. The main circulating metabolite, which is formed as a result of N-desmethylation of sildenafil, undergoes further metabolism.
According to the selectivity of action on PDE, the metabolite is comparable to sildenafil, and its activity against PDE5 in vitro is approximately 50% of the activity of sildenafil itself. The concentration of the metabolite in plasma is approximately 40% of that of levitra. N-desmethylmethabolite undergoes further metabolism; its terminal T1/2 is about 4 hours.