^ Well tha varies from person to person; it is pretty much all about the 2D CYP ?enzyme?300-400mg is a rough line to go buy, However, assuming APAP is not a problem, a half a gram can be taken in some, if not my people. Typically, IIRC, 2.5-10% of a codiene dose is converted to to its primary chive metabolite, Morphine; however, in extensive or Ultra Rapid metabolizers this could be doubled, 5-20%(metabolizers this could be doubled, 5-20% ( 10-15% average?) so it varies Of course there is a limit; probably a gram per day,(w/out APAP/Tylenol) though some prop could take 250-500mg, 2 or 3 times per diemAlso, Cg3 is a secondary Active or Semi -Active metabolite, which likely contributes something So yes, a hepatic prodrug with a ceiling of effect, though it varies. Unfortunately Codiene causes a large histamine release and side effects, so experimentation is hardly worth it. Especially with little or no tolerance, it isn?t really worth experimenting; Start with say a tester dose, then a quarter gram; you can always redose >100 minutes later - next, 300-400mg, or if that wears well handled MAX 500mg, split into two doses, say a quarter gram, at least 40 minutes later another 125-250mgAnd no 2D inhibitors, especially 24-48 hours prior, and if you have to take Promethazine, take 12.5-25mg with first dose, another 12.5-25mg with second dose. Diphenhydramine is only a mild inhibitor, although it takes effect faster, so 12.5mg, followed by 25mg with second dose. Hydroxyzine is best, no inhibition, and no anticholinergic effects, nd amazing antihistamine that is quite relaxing, and even some mild anti-anxyiolysis makes it ideal; 20ng Or Cetirizine is also a medium - long lasting 2nd gen antihistamine So there is a ceiling, though it varies, person. Still, do a proper CWE & dose gradually, half a gram per day, or maybe 700-800divided into 3-4 doses is pretty much the max, and that requires an antihistamine - Though 500mg, then another ~ 200-300 mg MAX several hours later is the best you could probably get, and really ~ half a gram per day is more of a reasonable figure- just stating facts, mixed with some conjecture - hope this clarifies, again not dosing advice, start reasonably, just trying to demonstrate the difference between Pooe and Ultra Rapid metabolizers, and the more common extensive and intermediate metabolizers - be careful and safe, again educational purposes only, and some are estimates