Wow.
Ok, first off, if you want a faster onset, rectal isn't the way to go. Morphine's horrible lipid solubility makes rectal absorption slow and erratic. In fact in some cases the tmax of rectal is longer than the that of MScontin itself! So you might end up with a slower onset...
Second, Cmax from rectal is often lower than oral. So longer Tmax, lower Cmax... The only advantage then, would be the longer duration. But if you're breaking the time release, you clearly don't care about that.
In fairness, BA from rectal can be higher than oral, which leads me to believe it CAN be more effective, but this isn't reliable, and the slow absorption and increased duration mean that Cmax would, at best be the same as oral.
Also, this whole process is unnecessary. A university did an experiment, and with only 4ml of water extracted about 95% of a 60mg mscontin. Since the FDA allows time released medication to vary by 10%, making 95% effectively 100%, since it could be as low as 90% in any case.
Believe me, I IV morphine all the time, it is my DOC. And you do not need to go through this trouble to break the time release. Maybe some brands are harder than others, but I've used multiple brands and have never had any trouble, and of course the university did it in a matter of with 4-5ml of water.
I fucking love morphine, but this is more than a typical user would go through, and it is unnecessary.(With most brands, I'll grant that some may be harder,, and require some project like this.)
If you want morphine to hit harder and faster, break the time release, and take it orally with baking Soda.