Sildenafil (Viagra)

Sildenafil inhibits phosphodiesterase type 5 (PDE5), relaxes smooth muscle, and increases levels of cGMP and blood flow to the corpus cavernosum. Sildenafil at recommended doses has no effect in the absence of sexual stimulation. The recommended dose is 50 mg taken as needed approximately 1 hour before sexual activity, but it may be taken anywhere from 0.5 hour to 4 hours before sexual activity. Sildenafil is known to enhance the hypotensive effects of nitrates. Thus, nitrates in any form are contraindicated with sildenafil use.

Discussion

The effect of sildenafil on AD was reported in one small RCT (Sheel et al. 2005). Although sildenafil decreased resting BP, no effect on the magnitude of AD resulting from penile vibrostimulation in men with SCI was observed.

Conclusion

There is level 2 evidence (from one RCT) (Sheel et al. 2005) that sildenafil citrate had no effect on changes in BP during episodes of AD initiated by vibrostimulation in men with SCI.