I took Zolpidem (Ambien) last night for the first time. It was p...

I took Zolpidem (Ambien) last night for the first time. It was prescribed to me by my oncologist as I have been having trouble sleeping ever since I have started chemotherapy for breast cancer one week ago. I fell asleep quickly and slept well for 5 hours, but awoke at 2am with a headache. I took 1 gram of Tylenol at 2am but was unable to go back to sleep because the headache became increasingly worse and did not go away until I drank some coffee at 5am. It was the worse headache I have ever had. The caffeine made it go away finally.