About 2 and a half weeks ago, I started taking allopurinol, and decreased my dose of mercpatopurine. For the past 4 days, I have had a non-stop headache. I can't find anything that the two medications combined would cause the headaches, but nothing else has really changed, unless you count the weather getting significantly colder. I usually get headaches due to humidity, not cold weather. Could the new medications be causing these headaches? I'm waiting for the doctor to call me back tomorrow, but just wondering about this.