Page 51 Guide to Pain Management in Low-Resource Settings

Chapter 7

Opioids in Pain Medicine

Michael Schäfer

Classifi cation of opioids introduction of the glass syringe by the French ortho-
pedic surgeon Charles Pravaz (1844), much easier han-
Treatment of pain very quickly reaches its limits. Any- dling of this unique opioid substance became possible
one who has suff ered from a severe injury, a renal or gall with fewer side eff ects.
bladder colic, a childbirth, a surgical intervention, or an Today we distinguish naturally occurring opi-
infi ltrating cancer has had this terrible experience and oids such as morphine, codeine, and noscapine from
may have experienced the soothing feeling of gradual semisynthetic opioids such as hydromorphone, oxy-
pain relief, once an opioid has been administered. In codone, diacetylmorphine (heroin) and from fully syn-
contrast to many other pain killers, opioids are still the thetic opioids such as nalbuphine, methadone, pentazo-
most potent analgesic drugs that are able to control se- cine, fentanyl, alfentanil, sufentanil, and remifentanil.
vere pain states. Th is quality of opioids was known dur- All these substances are classifi ed as opioids, including
ing early history, and opium, the dried milky juice of the the endogenous opioid peptides such as endorphin, en-
poppy fl ower, Papaver somniferum, was harvested not kephalin, and dynorphin which are short peptides se-
only for its euphoric eff ect but also for its very powerful creted from the central nervous system under moments
analgesic eff ect. Originally grown in diff erent countries of severe pain or stress, or both.
of Arabia, the plant was introduced by traders to other
places such as India, China, and Europe at the begin- Opioid receptors and
ning of the 14th century. mechanism of action
At that time, the use of opium for the treatment
of pain had several limitations: it was an assortment Opioids exert their eff ects through binding to opi-
of at least 20 diff erent opium alkaloids (i.e., substances oid receptors which are complex proteins embedded
isolated from the plant), with very divergent modes of within the cell membrane of neurons. Th ese recep-
action. Overdosing occurred quite often, with many tors for opioids were fi rst discovered within specif-
unwanted side eff ects including respiratory depres- ic, pain related brain areas such as the thalamus, the
sion, and, because of irregular use, the euphoric eff ects midbrain region, the spinal cord and the primary sen-
quickly resulted in addiction. sory neurons. Accordingly, opioids produce potent
With the isolation of a single alkaloid, mor- analgesia when given systemically (e.g., via oral, intra-
phine, from poppy fl ower juice by the German phar- venous, subcutaneous, transcutaneous, or intramus-
macist Friedrich Wilhelm Sertürner (1806) and the cular routes), spinally (e.g., via intrathecal or epidural

Guide to Pain Management in Low-Resource Settings, edited by Andreas Kopf and Nilesh B. Patel. IASP, Seattle, © 2010. No responsibility is assumed by IASP 39
for any injury and/or damage to persons or property as a matter of product liability, negligence, or from any use of any methods, products, instruction, or
ideas contained in the material herein. Because of the rapid advances in the medical sciences, the publisher recommends that there should be independent
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recommendation by the editors, authors, or IASP in favor of other medical products or procedures that are not covered in the text.