Analgesic drugs clinical evaluation

Much attention continues to be directed towards compounds of this class as a result of their now well-established analgesic properties in man, and the subject has been well reviewed [7, 180, 181]. The discovery that nalorphine was equi-potent with morphine in man, accidently revealed during studies of morphine-nalorphine mixtures [158, 182, 183], led to the clinical evaluation of other narcotic antagonists (both proven and potential) and has culminated in the development of the valuable drug pentazocine. Specific compounds of importance are considered below. 

Subsequent animal tests indicated that butorphanol is about 4 times more potent than morphine as an analgesic and equivalent to nalorphine as an antagonist. Clinical evaluation shows that butorphanol is also an effective analgesic in man (approximately 5 times more potent than morphine), and the tartrate is now marketed as an injection (Stadol). In animals its PDC is low (less than that of pentazocine) as it is in man, and this fact and its ceiling rather than dose-related effect on respiration (see p. 414) are recommendations for clinical use of the drug.<5,64)... 

It is easy to establish the truth or falsehood of the qualitative statement that a given drug has pain-relieving properties. It is much more difficult to establish that one analgesic is more valuable than another. Comparison of the clinical value of analgesic drugs requires quantitative data for the evaluation of analgesic properties and of undesired side effects. 

Much knowledge had been gained the techniques of clinical evaluation were improved, quantitation of drug-dependence was perfected at Lexington and analgesic assays in rodents were developed to the point where quantitative as well as qualitative prediction of clinical activity was extremely accurate. Most laboratories settled on some variant of Eddy s mouse hotplate test or the D Amour-Smith rat tail flick procedure. 

Rosekrans, P. C. M., Stoyanova, M., Mak, M., Cats, A. and Steiner, F. J. (1976) A comparative study of sulindac (MK-231), aspirin and placebo in coxarthritis some problems related to the clinical evaluation of analgesic, anti-inflammatory drugs. Pharmatherapeutica, 7,52. 

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