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New Perspectives on the Oldest Drug

Abstract of a paper for
1st Pan African Congress on Pain
Alexandria 9-11 November
(see meetings sections)

Geoff Gourlay
Pain Management Unit, Flinders Medical Centre, Bedford Park, South Australia, AUSTRALIA 5042


Morphine (in various galenical preparations as well as modem formulations) has been used to treat pain since recorded history. While morphine shows few of the pharmacological properties of the hypothetical “ideal” opioid agent, physicians have adapted to its limitations and can effectively use this valuable drug. Nevertheless, there are still gaps in our pharmacological knowledge of this widely used drug. In more recent times, we know that the administration of morphine with food can influence the blood morphine concentration — time curve compared to the fasting state, particularly when administered as an immediate release solution. While the inter-patient variability in the oral bioavailability of morphine is considerable (ranging from 10 % to 50%), the intra-patient variability in morphine absorption of from solution is more reproducible under standard conditions when repeatedly measured in the same patient. In addition, there is chronopharmacokinetic variability in morphine blood concentrations from both immediate release and modified release formulations; ie the absorption of morphine varies depending on the time of the day the dose is administered. The new modified release formulations are not bio-equivalent and therefore, patients should be retitrated to effective pain relief if physicians elect to change formulations. This presentation will consider these newer aspects of morphine pharmacology. A knowledge of these pharmacokinetic aspects of will allow physicians to more effectively use this drug which is generally regarded as the “drug of choice” for acute, chronic and cancer pain.

See also:

Pharmacokinetics of opioids
Evidence based analgesic league table

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