World Health Organization Ladder
The WHO ladder portrays a progression in the doses and types of analgesic drugs for effective pain management. The best choice of modality often changes as the patient’s condition and the characteristics of the pain change.
The first step in this approach is the use of acetaminophen, aspirin, or another Non-steroidal Anti-inflammatory Drug (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. 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 non-opioid analgesic should be used to avoid exceeding maximally recommended doses of acetaminophen or NSAID.
Pain that is persistent or is of moderate to severe intensity from the outset should be treated by increasing the dosage or with more potent opioids. Drugs such as codeine or hydrocodone are replaced with more potent opioids (usually morphine, hydromorphone, methadone, fentanyl, or levarphanol).
Medications for persistent cancer-related pain should be administered on an around-the-clock schedule, 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.
Reference: U.S. Department of Health and Human Services, Agency for Health Care Policy and Research Clinical Practice Guidelines, Number 9, March 1994.