You mean I eat calcium carbonate and and my methadone dose works better? Jesus, and there isn't a single day I don't hold a piece of chalk in my hand... I even used to eat chalk long time ago and that was justified by a doctor stating that my organism supplements calcium in this way. And no, it isn't calcium sulfate dihydrate.
Is it another myth or is it for real? And is it about calcium carbonate?
EDIT: Yeah, it's CaCO3 and MgCO3. Magnesium works good for constipation BTW.
I know where this comes from... Methadone "likes" alkaline environment better, it absorbs from stomach better when pH is higher. So basically, you could even drink sodium dicarbonate water solution to get the same effect. It's not about some magic in Tums (R), it's just chemistry. And both calcium carbonate and magnesium carbonate have slightly alkaline reaction but to such an extent it doesn't hurt your stomach so it's OTC.
So, it's not about methadone metabolism change. It's about methadone absorption rate which can really vary orally depending on pH in your stomach. I guess they should start adding some weak antacid to syrups and tablets as 90% absorption rate is demanded, right? And it can drop to 50% or even less...