In answer to your question, YES, sometimes viagra does work that fast! Thats how it worked for us too one week after the catheter came out and it has only has got better since then.
All the best to you and yours,
Husband diagnosed May 2006 at age 50. RRP performed 13 July 06.
PSA 5.7, Gleason 3+4=7, Staged T2C, Cancer confined to prostate.
His father diagnosed at age 62 and is currently a 13 year survivor!