I wouldn't go over 15 mg with instant-release oral morphine, considering 10 mg of oxycodone or hydrocodone gets you fairly high. And, I'd suggest you find out what kind of extended-release morphine you have, because MS-Contin is different than Kadian is different than Avinza, and so on, and so the time-release mechanisms are not the same and cannot be treated the same. Frankly, I know very little about defeating time-release mechanisms with any pharmaceuticals, really. But, with your very, very low tolerance, BE careful with 50 mg morphine; certainly don't take all of it at once, even if it is still time-release.