SILDENAFIL CITRATE-50 mg (SOFT TABLETS)
PENEGRA-50 Soft Chew (Sildenafil citrate soft) tabs are an oral therapy for erectile dysfunction. Sildenafil citrate soft tabs are derived from the citrate salt of sildenafil, a selective inhibitor of cyclic guanosine monophosphate (cGMP)-specific phosphodiesterase type 5 (PDE5). Sildenafil citrate is designated chemically as 1-[[3-(6,7-dihydro-1-methyl-7-oxo-3-propyl-1H-pyrazolo[4,3-d]pyrimidin-5-yl)-4-ethoxyphenyl]sulfonyl]-4-methylpiperazine citrate. Sildenafil citrate is a white to off-white crystalline powder with a solubility of 3.5 mg/ml in water and a molecular weight of 666.7. Sildenafil citrate soft tabs are formulated as blue, film-coated diamond-shaped tablets equivalent to 25 mg, 50 mg and 100 mg of sildenafil for oral administration for erectile dyfunction.
In addition to the active ingredient, sildenafil citrate, each sildenafil citrate soft tablet contains the following inactive ingredients: microcrystalline cellulose, maize starch, povidone, magnesium stearate, colloidal silicon dioxide, hydroxypropyl methylcellulose, titanium dioxide, indigo carmine colour. Mechanism of Action The physiologic mechanism of erection of the penis involves release of nitric oxide (NO) in the corpus cavernosum during sexual stimulation. The nitric oxide then activates the enzyme guanylate cyclase, which results in increased levels of cyclic guanosine monophosphate (cGMP), producing smooth muscle relaxation in the corpus cavernosum and allowing inflow of blood.
Sildenafil (i.e. sildenafil citrate) has no direct relaxant effect on isolated human corpus cavernosum, but enhances the effect of nitric oxide by inhibiting phosphodiesterase type 5 (PDE5), which is responsible for degradation of cGMP in the corpus cavernosum. When sexual stimulation causes local release of NO, inhibition of PDE5 by sildenafil citrate soft tabs causes increased levels of cGMP in the corpus cavernosum, resulting in smooth muscle relaxation and inflow of blood to the corpus cavernosum. Sildenafil citrate soft tabs at recommended doses have no effect in the absence of sexual stimulation. In addition to human corpus cavernosum smooth muscle, PDE5 is also found in lower concentrations in other tissues including platelets, vascular and visceral smooth muscle, and skeletal muscle. The inhibition of PDE5 in these tissues by sildenafil citrate soft tabs may be the basis for the enhanced platelet antiaggregatory activity of nitric oxide observed in vitro, an inhibition of platelet thrombus formation in vivo and peripheral arterial-venous dilatation in vivo. Indications Sildenafil citrate soft tabs are indicated for the treatment of erectile dysfunction