I am a 79 year old prostate cancer survivor, suffering from BPH and ED. I like the idea of treating them both with the same drug. The dosage of 5mg/day is good for BHP, but does not help my ED; 10mg helps somewhat but not enough. Is it safe to bump it up to 20mg, and then go back to 5mg? I was taking Flomax for the BPH for awhile, but I was advised to skip it if I planned to use viagra that night because of the danger of low blood pressure. I switched to Cialis about 6 weeks ago.