Cancer pain management

American Journal of Pharmaceutical Education, Summer 1998 by Skaer, Tracy L

As stated previously, there is a high degree of interpatient variability in each patient's response to narcotics(7,10). Some patients will require small doses to effectively control their pain, while others may need significantly larger doses to produce the desired effect. Low doses (ie. 10mg tablets or solution) of morphine IR for narcotic naive patients should be used initially, followed by upward titration until adequate analgesia is experienced. There is no maximum dose of morphine for patients with severe pain.

Patients unresponsive to oral morphine (e.g., malabsorption syndromes) can often be effectively managed with continuous subcutaneous morphine administration via portable ambulatory infusion devices. thereby obviating the need for frequent painful intramuscular injections or a long term intravenous access site(32,34). Morphine can also be administered rectally using the suppository formulation (available in 5, 10, 20, and 30mg doses)(35,38). Systemic absorption via the rectal route is similar to the oral route of morphine administration(39). No more than two suppositories should be administered rectally at one time. Therefore, the usefulness of commercially available suppositories are limited to those patients requiring doses of 60mg or less administered every three to four hours. Finally, morphine can be administered via the epidural or intrathecal route(36). However, more controlled clinical studies are required to document the optimal dose and the advantages in selecting these routes of administration for chronic cancer pain management over the other routes already discussed.

Oxycodone

Oxycodone in combination with acetaminophen is often prescribed for distressing to intense pain (pain score of 3 on a scale of 0 to 5)(6). Oxycodone's short half-life requiring doses every three to four hours in most patients, and potential for acetaminophen toxicity has limited the use of the combination product to patients with pain scores of up to 3 only(6). However, a sustained release formulation of oxycodone dosed every 12 hours is now available. Oxycodone SR is a useful alternative to morphine SR(6).

Hydromorphone

Hydromorphone is a potent, safe, and effective narcotic agent that is essentially interchangeable with morphine in its efficacy for patients with advanced cancer(6,20). Hydromorphone is four times as potent as morphine, allowing for smaller injection or infusion volumes for patients requiring parenteral administration(6,20). Hydromorphone is also available as a 3 mg suppository. Again, as with the morphine suppositories, only two of these 3 mg dosage units can be administered rectally at one time, thereby limiting pain control via this route to a maximum dose of 6 mg or less given every four to six hours. Currently, there are no advantages of selecting oral hydromorphone over oral morphine. Morphine SR preparations scheduled every 8 to 12 hours are preferable to hydromorphone IR administered every three to four hours. However, a hydromorphone SR formulation has been developed and should be available in the United States in the near future(40).