MS Contin is morphine sulfate. OxyContin is oxycodone. Both are opioid medications, with morphine being a natural opiate and oxycodone being synthetic.
I think that MS Contin is much better than Oxycontin, in fact the best pain reliever I've ever had. Oxycontin - which I happened to discover in a rural area of the Andes, seems like Percodan, but longer lasting. I've always felt Percodan/Percocet are problematic for long term chronic pain. They don't last long. They deliver unpredictable pain relief. Tolerance is easy to develop. And they're too enjoyable. I never wanted to take them as my main source of pain relief, so for years I took Vicodin-ES and occasionally, Percodan. Then the Vicodin quit working and I developed a second and truly crippling pain problem. So I went to a pain clinic. I learned that Oxycontin was an excellent pain reliever, but had gotten a bad reputation because it could be melted down and injected. MS Contin can't be melted down. This is not something I ever considered, I must say. The reason I mention it is that morphine is less likely to get a bad reputation and become harder to obtain. I was a little concerned about taking Morphine, but I knew my Mother had been given Morphine shots for cramps as a teenager and considered it a lifesaver.
The main thing is that the pills work perfectly, after fooling around with the dosages. When I first started I was given the long lasting form twice a day. That doesn't work for me as they only lasted a few hours and I was spending the rest of the day in pain.
I'm now on 60 mg. 4 times a day. They feel like they are slow-release. They always work; I don't notice a tolerance and they never make me feel too good, if you know what I mean. I don't want to feel anything. The only big problem is a no pain - big gain: I weigh about 30 pounds more than I did when I started taking them. I also get sleepy earlier, but I don't consider that a biggy. Particularly when I think of all the painfree days that I have enjoyed after 30 years of chronic pain.