benign prostatic hyperplasia
"Had problems immediately (Tiredness after 7-10 days) with Flomax and so doctor proscribed Proscar and it helped somewhat.  However, It caused me to feel tired and occasionally extreme exhaustion.  After about one year of use I became impotent even with Viagra.  I quit it for about 6 weeks.  Felt normal with no erectile dysfunction.  Started again and felt tired and had ED.  Quit for about 2 months again and felt OK. Started a third time with the same tiredness and ED problems.  Have now stopped using it."