(5.99), is even more useful, since it is longer acting. Levallorphan (5.100) and cyclorphan
(5.101) are morphinane derivatives, whereas oxilorphan (5.102) is their 14-OH analog.
The cyclobutyl homolog of oxilorphan, butorphanol (5.103), is 4–10 times more active
than morphine, has 50–70 times the activity of pentazocine as an analgesic, and 30 times
the activity of pentazocine as an antagonist.
In the benzomorphan series, cyclazocine and pentazocine are useful mixed agonist–
antagonists. Unfortunately, the former has considerable hallucinogenic properties,
although pentazocine is a very useful analgesic. Among the oripavines, buprenorphine
(5.104) and diprenorphine (5.105) are valuable agonist–antagonists.
5.19 PEPTIDE HORMONES OF THE THYROID AND
PARATHYROID GLANDS
The thyroid and parathyroid glands are two important endocrine organs that are heavily
committed to the biosynthesis of hormones as chemical messengers. The thyroid gland,
which surrounds the larynx, has an enormous variety of metabolic functions. It is itself
regulated by thyroliberin, which in turn regulates production of thyrotropin(thyroid
HORMONES AND THEIR RECEPTORS 359