Pain control in the ambulatory elderly. Pain control in the elderly, no matter what the etiology or setting, can be a major clinical challenge. Aging causes unique physiologic changes, eg, a decreased perception of pain and an enhanced sensitivity to opioid analgesics. Principles regarding evaluation of patients with pain are reviewed, including the use of an objective instrument for pain assessment from the viewpoint of both physician and patient. Good pain control can be achieved with the nonopioids, such as acetaminophen and the nonsteroidal anti-inflammatory drugs, the opioid analgesics, and, in some cases, adjuvant agents. Discussed also are the concerns for patient addiction and the WHO Cancer Pain Relief program. 