Eur J Pain
2001;5 Suppl A:49-57
Trends in the
pharmacology of opioids: implications for the
pharmacotherapy of pain.
Mather LE
Professor of Anaesthesia and Analgesia (Research), Centre for Anaesthesia and Pain Management
Research, University of Sydney at Royal North
Shore Hospital, Sydney, Australia
Some
25 years ago, it was popular to write a figurative
equation for drug treatment: Patient + drug-->effect.
Clearly, this was too simplistic for the reliable
pharmacotherapy of pain. The 'patient' with pain
is a complex individual and the 'drug' is not the
same in effect to every patient, regardless of
being an opioid analgesic. Besides, the 'effect'
needs specification: it really means an acceptable
balance between therapeutic and side-effect-to
that patient. These days, neural plasticity and
neuromodulation associated with nociception are
well-known. Psychological involvement in the
physical domain of nociception is similarly
well-known. Given these complexities, it is
surprising that the pharmacological control of
pain through the application of relatively simple
analgesics can be so effective. Opioid analgesics
have been administered by every possible route.
Because the degree of invasion of the patient
differs between routes, the balance between
simplicity, aesthetic appeal, and efficacy of the
various routes needs to be considered. The
effectiveness of opioid analgesics depends in
large measure on the application of the right
agent, in the right dose, by the right route, at
the right time for that patient. To assist in this
task, researchers have produced patient-controlled
analgesia
and 'pharmacologically engineered' analgetic
molecules to achieve receptor selectivity and
pharmacokinetic predictability. Also, much
relevant data concerning the time courses of
analgetic drug (+/- metabolite) concentrations in
the body and in the ways in which these properties
are modified by different normal and
pathophysiological variations have been gathered,
and the philosophy of 'opioid rotation' has arisen
to maintain therapeutic benefits when tolerance or
metabolite-induced side-effects prevail. This
essay discusses some of the trends in opioid
pharmacotherapy over the past 25 years. Copyright
2001 European Federation of Chapters of the
International Association for the Study of Pain.
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