A simple, well-validated, and effective method for assuring the rational titration of therapy for cancer pain has been devised by WHO (World Health Organization, 1990). It has been shown to be effective in relieving pain for approximately 90 percent of patients with cancer (Ventafridda, Caraceni, and Gamba, 1990) and over 75 percent of cancer patients who are terminally ill (Grond, Zech, Schug, et al., 1991). This approach is based on the concept of an analgesic ladder (Figure 2).
The five essential concepts in the WHO approach to drug therapy of cancer pain are:
The first step in this approach is the use of acetaminophen, aspirin, or another NSAID for mild to moderate pain. Adjuvant drugs to enhance analgesic efficacy, treat concurrent symptoms that exacerbate pain, and provide independent analgesic activity for specific types of pain may be used at any step.
When pain persists or increases, an opioid such as codeine or hydrocodone should be added (not substituted) to the NSAID. Opioids at this step are often administered in fixed dose combinations with acetaminophen or aspirin because this combination provides additive analgesia (Weingart, Sorkness, and Earhart, 1985). Fixed-combination products may be limited by the content of acetaminophen or NSAID, which may produce dose-related toxicity. When higher doses of opioid are necessary, the third step is used. At this step separate dosage forms of the opioid and nonopioid analgesic should be used to avoid exceeding maximally recommended doses of acetaminophen or NSAID.
Pain that is persistent, or moderate to severe at the outset, should be treated by increasing opioid potency or using higher dosages. Drugs such as codeine or hydrocodone are replaced with more potent opioids (usually morphine, hydromorphonet methadone, fentanyl, or levorphanol), as described below.
Medications for persistent cancer-related pain should be administered on an around-the-clock basis, with additional "as-needed" doses, because regularly scheduled dosing maintains a constant level of drug in the body and helps to prevent a recurrence of pain. Patients who have moderate to severe pain when first seen by the clinician should be started at the second or third step of the ladder.
Patient-Controlled Analgesia (PCA)
Figure 2: The WHO Ladder
Dose Equivalence Table for Opioid Analgesics in Opioid-naive Adults and Children greater than or equal to 50kg body weight.
Dose Equivalence Table for Opioid Analgesics in Opioid-naive Adults and Children less than 50kg body weight.