Whoops accidentally deleted my last post when I tried to edit. I'm just sick of people saying GFJ won't potenate codeine, yet it inhibits the enzymes that break it down into inactive metabolites (CYP3A4) and doesn't inhibit the enzyme that turns it into morphine (CYP2D6). Paracelsus tried to clear this up but people keep spreading misinformation.
That's an important bit of information. I should've included the specific enzymes at play here. Not all Opioids are metabolized by the same groups of enzymes and many, like Methadone for instance, are broken down in a substantial way, by several different enzyme systems.
I'm in agreement with TrippyZebra in regards to his point about misinformation, which is what I was scratching at in my last post in this thread. We all need to be as sure as possible before interjecting into a debate about this sort of thing. Sure, it may seem like small potatoes, dealing with a drug as seemingly mild as Codeine, but Codeine is capable of and does kill, all the time. To say that a 10% potentiation through enzyme changes via GFJ or what have you couldn't kill is very optimistic thinking.
For the record, all available information seems to imply that Codeine is made more potent by administration with substances like GFJ. What is the rate of said potentiation? - This is the more difficult question to answer. There are myriad substances which effect the functioning of our body's enzymes though ranging from OTC medication, prescription medication, nutritional/herbal supplements and as we've seen here, even food. For instance, coadministration of the SSRI-type antidepressant Fluvoxamine (Luvox) in patients or users of Methadone has been documented in plurarlity to lead to potentially fatal overdose and toxicity in individuals that previously experienced minimal side effects i.e. sedation/drowsiness.
It's my personal opinion that Codeine has become mired in misinformation about its range of effects because it has never really "caught on" by use of any route other than oral. For those needing more powerful analgesia, the logical jump has always been Morphine, as opposed to further administration of Codeine. This has left us and the medical community with little need to understand the drug by varying ROA's. I'm not saying we know nothing, but I think it's safe to say we know more about parenteral administration of Morphine than we do for Codeine.
Also, further for the record, Codeine has historically been distributed in virtually all forms, Intravenous being contradindicated by virtue of the potential for deadly anaphalaxysis. There have been Codeine injectables (IM/SC) and suppositories in the past, when it would seem that the drug was more in vogue. It wasn't so long ago that Codeine was treated in the States like it is in Europe and Canada, as an OTC medication, generally considered outside the bounds of a "full Opioid narcotic". I'm sure this played a role when disucssing cases of celebrities like Howard Hughes who was addicted to the shit as a Drug of Choice. As doctors have desired greater control over analgesia, agents like the shorter-acting Hydromorphone (Dilaudid) have become the new(er) gold standard. Something like Codeine just isn't appropriate given its range of bioavailability and not to mention the plethora of varying levels of metabolization from person to person and race to race.