Avoiding polypharmacy in treating chronic pain

Nursing, Sep 1995 by Hinnant, Debbie

FAY MARCH, 57, WHO HAS ADENOCARCINOMA of the lung, has been hospitalized for pain control. Her doctor orders three opioid analgesics:

* morphine, 10 mg I.M., every 4 hours, p.r.n.

* acetaminophen with codeine phosphate No. 3, one or two tablets P.O., every 3 hours, p.r.n.

* oxycodone, 10 mg P.O., every 3 hours, p.r.n.

In one 24-hour period, Mrs. March receives all three opioid analgesics at irregular intervals. Her pain ratings range from 6 to 8 on a scale of 0 to 10.

Reviewing your options

Which of the following responses is the most appropriate?

a. Remind Mrs. March that "p.r.n." means she's responsible for telling the nurses when she needs pain medication.

b. Ask the doctor to switch her to immediate-release P.O. morphine every 4 hours, then to sustained-release morphine every 12 hours when her pain is under control.

c. Ask the doctor to increase her morphine dose to 15 mg I.M. every 4 hours, p.r.n.

d. Express your concern to the doctor that Mrs. March may be developing an addiction because the combination of three opioids isn't relieving her pain.

Making the right choice

The correct response is b. Using multiple opioids has no advantage.

Morphine is the standard first-line opioid for chronic cancer pain. Using an equianalgesic chart, you can convert Mrs. March's present total 24-hour opioid analgesic intake to an equianalgesic oral dose of immediate-release morphine. (The Agency for Health Care Policy and Research [AHCPR] Clinical Practice Guideline for Management of Cancer Pain contains an equianalgesic chart on page 52.)

Give immediate-release morphine every 4 hours until you achieve good pain control. Then calculate the total 24-hour dosage and divide it into two doses of sustained-release morphine to be given every 12 hours.

The dose may need adjusting; depending on Mrs. March's response. If she has breakthrough pain more than twice in 24 hours, for example, the doctor may increase the dose of sustained-release morphine in 25% to 50% increments.

Response a is incorrect. Although Mrs. March should understand what "p.r.n." dosing means, you shouldn't place full responsibility for pain control on her. And remember, as-needed dosing won't relieve continuous pain adequately. The AHCPR says, "Because many patients have persistent or daily pain, it's important to use opioids on a regular schedule rather than only 'as needed.' Around-the-clock administration of analgesics allows each dose to become effective before the previous dose has lost its effectiveness."

Response c isn't the best choice, even though it boosts the morphine dose. The I.M. route is the least desirable route because it's painful and the drug is irregularly absorbed.

Response d illustrates a common misconception that some people have regarding addiction. Addiction is a behavior characterized by compulsive drug seeking for reasons other than medical use. Research shows that far less than 1% of patients taking opioid analgesics for pain ever become addicted.

Continuous pain is better controlled by giving sufficient, regular doses of one opioid, rather than by adding others. When given in appropriate doses, a single oral opioid is as effective as a parenteral opioid.