Testing and evaluation of opiate analgesics and antagonists.

In recent years many advances have been made in our understanding of how opiates function as modulators of pain. These discoveries have in turn led to substantial improvements in the methodology available for the testing of newly synthesized opiates. Preliminary in vitro assays can now define opiate receptor selectivity and also classify a drug as a pure or mixed agonist-antagonist. These results can then be verified by in vivo behavioral or neurochemical studies using laboratory animals. This protocol, which involves tests that are relatively simple and inexpensive to conduct, yields reproducible results which provide insight into the study design required for the clinical evaluation of the new agents. Considering the complexity of the problem involved in modifying the pharmacological profile of an opiate, the progress that has been made in the methodology for evaluating these substances is commendable.