Sildenafil citrate as a phosphodiesterase inhibitor has an antioxidant effect in the blood of men

J Clin Pharm Ther. 2008 Dec;33(6):635-40. doi: 10.1111/j.1365-2710.2008.00962.x.


Background and objective: Sildenafil citrate enhances the action of nitric oxide by preventing the hydrolysis of cGMP, and is widely used to treat erectile dysfunction. We investigated the effects of sildenafil citrate administration on lipid peroxidation and antioxidant redox enzymes in blood of healthy men.

Method: Thirty healthy male subjects were divided equally into two groups. The first group was used as the control. A single dose of sildenafil citrate was administrated orally to subjects constituting the second group. Blood samples were obtained at 0, 2, 6 and 24 h after intake of the single dose of 100 mg sildenafil citrate or placebo.

Results and discussion: The dose of sildenafil citrate resulted in significant increase in the erythrocyte superoxide dismutase and catalase activities at 6 and 24 h. Plasma lipid peroxidation levels decreased slightly. There was no statistical difference in erythrocyte glutathione peroxidase activity between the placebo and sildenafil citrate groups.

Conclusion: Treatment of blood with 100 mg sildenafil citrate has protective effects on oxidative stress by inhibiting free radical formation and by supporting antioxidant redox systems.

Publication types

  • Randomized Controlled Trial

MeSH terms

  • Adult
  • Antioxidants / pharmacology*
  • Catalase / drug effects
  • Catalase / metabolism
  • Cyclic GMP / metabolism
  • Humans
  • Lipid Peroxidation / drug effects*
  • Male
  • Nitric Oxide / metabolism
  • Oxidation-Reduction / drug effects
  • Oxidative Stress / drug effects
  • Phosphodiesterase Inhibitors / pharmacology*
  • Piperazines / pharmacology*
  • Purines / pharmacology
  • Sildenafil Citrate
  • Sulfones / pharmacology*
  • Superoxide Dismutase / drug effects
  • Superoxide Dismutase / metabolism
  • Time Factors
  • Young Adult


  • Antioxidants
  • Phosphodiesterase Inhibitors
  • Piperazines
  • Purines
  • Sulfones
  • Nitric Oxide
  • Sildenafil Citrate
  • Catalase
  • Superoxide Dismutase
  • Cyclic GMP