Sildenafil citrate (SC or Viagra) is an oral medication widely used to treat erectile dysfunction and maintains a sufficient erection for satisfactory sexual performance. The side effects of sildenafil citrate have been reported.
Aim of the work: The present study was designed to investigate the effect of sildenafil citrate in the therapeutic dose in different regimes.
Materials and methods: This study included forty senile male albino rats divided into four equal groups. Group (A) was used as a control group (did not receive any treatment). Group (B) receive the therapeutic dose of Viagra (1.5 mg suspended in 1.5 ml distilled water) orally using a gastric gavage as daily dose for one week. Group (C) received the therapeutic dose of Viagra 3 times / week for two weeks. Group (D) received the therapeutic dose of Viagra each week for 4 weeks. Half of the treated rats of the different groups were sacrificed, other half were sacrificed after two weeks from the last dose as recovery groups (RB, RC and RD). The testes were dissected and blocked in paraffin. Hematoxylin and Eosin (HX&E) and Periodic acid Schiff stain (PAS) were applied and serum testosterone levels in the different groups were evaluated.
Results: The present study showed that the therapeutic dose of sildenafil caused several  histological findings in the germinal epithelial of the rat testes including degeneration , detachment  of the spermatogenic cells especially the primary spermatocytes with  addition thickening of the basement membranes of the seminiferous  tubules  and increased interstitial Leydig cells. The serum testosterone of the treated rats showed increased level of testosterone especially in group D. The recovery rats showed relative improvement of parameter toward normal.
Conclusion: Sildenafilproduce morphological and histological alterations in the testes.