Thanks McDoctor for bringing this back up again. I meant to post a comment then went out of town & forgot about it.
I agree with your statements. Addiction, dependence, abuse & tolerance are all interrelated with not just the drug, but also the patient & condition being treated. Drugs like Soma, which McDoctor brought up, altho not controlled will metabolize to an addictive substance (in Soma's case - its metabolized to meprobamate) thus needs to be watched closely.
You can't really compare tolerance toward benzodiazepines to tolerance to opioids. They work on different receptors & affect different neurotransmitters. Also - there is no cross tolerance in many situations, but in others there is.
As McDoctor pointed out - the DEA classification is based upon risk of "diversion" and other political influences - thus you have Paregoric a CII in some states & a CIII in others. Likewise, at least until a few years ago, the CV cough syrups were controlled differently in some states than others.
You can find the relative potency within a class of drugs - your example of morphine & codeine in any pharmacology text. We use this information all the time to convert someone from a short acting opioid to a longer or different route. Anesthesiologists, surgeons, dentists, podiatrists & any other health professional who might do a surgical procedure also have to be cognizant of the relative potency of opioids since in their circumstance, they must cover the addiction before they can dose for pain of an acute intervention.
I don't think you'll find a simple chart, but come back if you need more help with a specific situation.
