I've had a bad sinus infection: pressure, fever, streaming nose, coughing up crap, etc. for 3 days. I went to the Doctor this morning, he wrote a Rx for a Z-Pak. I took the first two pills at 10:00am. By 1:00pm I felt SO MUCH BETTER!!! I still don't feel 100%, but considering that I felt like I had been hit by a truck for three days, just being able to do some minor household chores is amazing! This is my first time taking a Z-Pak. Does it really work that fast and that well?