What Causes Headache With Weakness And Shakes In Legs?

Hi Dr.Mimtz, this question is concerning my 83 year old father. I am his medical person that takes him to the doctor and his POA. The Dr. stated in his exam 3 days ago that his prostrate was enlarged and put him on Avodart took him off of flomax and replaced it with Rapaflo. The problem is for the last few days his legs have become very weak and shaky. (He stated that on leg felt numb) He also had a bad headache yesterday. He usually doesn't get headaches. Starting two medications at once makes it hard to determine what one could be causing what. Thank you kind sir. Have a great day.