Once a week is generally a good dosing regimen with opiates/opioids, provided you withstand the psychological pull to dose more often. Honestly, I use opiates fairly often and I'd get knocked the fuck out from 45 mg of oxy, tho I know several others who need to take far more than that to feel anything. Even with my consistent dosing schedule, I've managed to keep my dose low on just about all things.
Did you start out on a lower dose? Some people are genetically predisposed to not feel anything except higher doses of opiates and opioids, tho if you started out lower and can't feel anything except 45 mg of oxy, there's a chance you have a tolerance.