Morphine pharmacokinetics and analgesia after oral administration.

The well established use of oral morphine in the treatment of chronic cancer pain has developed empirically and a knowledge of its pharmacokinetics is not necessary in order to use the drug effectively. However recent information about the pharmacokinetics of morphine may help resolve the controversy about oral to parenteral relative potency ratios, and may also in the future shed some light on the problem of patients whose pain does not respond to morphine.