Typical examples include compounds such as morphine, codeine, and dextromethorphan (DXM).

Despite related molecular structures, the pharmacological profiles and mechanisms of action between the various types of morphinan substances can vary substantially.

Of the major naturally occurring opiates of the morphinan type—morphine, codeine and thebaine—thebaine has no therapeutic properties (it causes seizures in mammals), but it provides a low-cost feedstock for the industrial production of at least four semi-synthetic opiate agonists, including hydrocodone, hydromorphone, oxycodone and oxymorphone, and the opioid antagonist naloxone.

The addition of a two-carbon bridge between carbons 6 and 14 (e.g., 6,14-ethano, or 6,14-etheno), and which significantly distorts the C ring, may increase potency 1,000 to 10,000 times, or greater, compared to morphine, as in etorphine, and others.

The relative potency is thought to be associated with the degree of distortion of the C ring, and is perhaps greatest in diprenorphine, where this group is α,α-dimethyl-6,14-etheno.