McKenna's Pharmacology for Nursing, 2e

C H A P T E R 2 6 Opioids, opioid antagonists and antimigraine agents 403

Ergot derivatives constrict cranial blood vessels Triptans bind serotonin receptors to cause cranial vasoconstriction

■■ BOX 26.2  Differences in responses to opioid therapy

Because of physical and cultural differences among various ethnic groups, people from certain groups respond differently to particular medications. Nurses should keep in mind that people in some ethnic groups are genetically predisposed to metabolise medications differently. For example, people of Arab descent may not achieve the same pain relief from opioids as people in other ethnic groups; their inborn differences in metabolism may require larger doses to achieve therapeutic effects. Some African American people seem to have a decreased sensitivity to the pain-relieving qualities of some opioids, although the reason for this is unknown. Moreover, increasing the dosage of these medications may not increase the level of pain relief and actually may be toxic. In such cases, another class of medication might be used to “boost” the pain-relieving qualities of the opioid. Among some immigrant and first-generation Asian Americans, it may not be socially acceptable to show strong emotion, such as that associated with pain. The sensitive nurse will frequently ask such people if they are comfortable or require additional medication. Although many of these studies were done on American people, ethnic minority groups (e.g. Asians, people from the Middle East) are increasing in New Zealand and Australia. Therefore, healthcare providers will need to carefully monitor opioid responses of people from ethnic minority groups.

Opioid receptors

Cutaneous stimulation massage heat, cold vibration pain sensation

Narcotics occupy opioid receptors to block pain response

Pain sensation

Small- diameter fibres

Large- diameter fibres

Substantia gelatinosa

Gate open

Gate closed

Spinal cord

an analgesic that is long acting but not too sedating is desired for an outpatient, hydromorphone might fit those objectives. Fentanyl, which is available for injection, is also available as a lozenge for treating breakthrough pain, as a transdermal patch and in an ionic delivery system, which activates the release of the drug as needed for treating breakthrough pain in cancer people. See the Critical thinking scenario for information about using morphine to relieve pain. FIGURE 26.2  Sites of action. Opioid agonists occupy opioid receptors to block pain response. Ergot derivatives constrict cranial blood vessels and triptans bind serotonin receptors to cause cranial vasoconstriction. THE SITUATION L.M., a 25-year-old businessman, was in a car crash and suffered a fractured pelvis, a fractured left tibia, a fractured right humerus, and multiple contusions and abrasions. For the first 2 days after surgery to reduce the fractures, L.M. was heavily sedated. As healing progressed, he was taught to use a patient-controlled analgesia (PCA) system using morphine. PCA provides a baseline, constant infusion of morphine and gives the person control of the system to add bolus doses of morphine if they feel that pain is not being controlled. The system prevents overdose by locking out extra doses until a specific period of time has elapsed. L.M. became agitated when he was not able to

CRITICAL THINKING SCENARIO Using morphine to relieve pain

give himself a bolus because the appropriate time between boluses had not elapsed. The nurse working with L.M. noted an increase in blood pressure, pulse and respiration. L.M. had no fever. He did seem very anxious and rated his pain at 10. The nurse tried several non-pharmacological measures to alleviate the pain and spent time talking with L.M. and reassuring him. By day 5, L.M. was switched to an oral morphine and plans were made to wean him from the opioids. CRITICAL THINKING What basic principles must be included in the care plan for L.M.? Think about the difficult position the floor nurse