Sildenafil Citrate – Mechanism of Action


Sildenafil citrate is an active ingredient, used in production of oral medications for treatment of erectile dysfunction. On international pharmaceutical market, you may find:

  •     Oral tablets, containing Sildenafil citral
  •     Oral capsules, containing Sildenafil citrat
  •     Chewable tablets, containing Sildenafil citrate
  •     Oral jelly, containing Sildenafil citrate

The amount of active ingredient Sildenafil citrate in one dosage form is always indicated in milligrams (mg) only. Depending on the severity of erectile dysfunction, men can be prescribed tablets (capsules), containing 25mg, 50mg or 100mg of active substance Sildenafil citrate.

Mechanism of action

Sildenafil citrate is a PDE5 inhibitor, which pharmacological effect is to stimulate the blood inflow to erectile tissue of the penis. By increasing the blood flow to the erectile tissue, Sildenafil citrate helps to get erection, sufficient for intravaginal penetration.

It is known that Sildenafil citrate increases the natural physiological mechanism of erection, occurring only in response to sexual arousal. Therefore, after the intake of Sildenafil citrate man might need sexual stimulation (visual sexual stimuli and / or penis stimulation) to get a normal and sufficient erection.

Pharmacokinetic features of Sildenafil citrate

  • Sildenafil citrate is rapidly absorbed into the blood and undergoes hepatic metabolism.
  • An absolute bioavailability of Sildenafil citrate is about 40%.
  • An average half-life period of Sildenafil citrate and its active metabolites is approximately 4 hours.

Please note that some medications can exceed the concentration of Sildenafil citrate in the blood plasma and cause side effects. Therefore, before initiating erectile dysfunction treatment along with the treatment of other diseases, one should carefully learn the information on Sildenafil citrate drug interactions.

Absorption and Distribution of Sildenafil citrate

About 96% of Sildenafil citrate dose binds up with blood proteins. Maximal concentration of Sildenafil citrate in the blood plasma is observed in 30-120 minutes after the intake of a single dose on an empty stomach.

If Sildenafil citrate is taken prior, during or soon after meals, containing a large amount of fat:

  •         The increase of Sildenafil citrate concentration in the blood plasma is delayed up to 60 minutes.
  •         Concentration of Sildenafil citrate in the blood plasma can decrease up to 30%.

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