Adverse effects and cognitive function among primary care patients taking opioids for chronic nonmalignant pain.

Chronic opioid therapy is commonly prescribed for chronic nonmalignant pain. Few published data describe the adverse effects experienced by patients with chronic nonmalignant pain being treated by primary care physicians. A prevalence study was conducted on a sample of 1,009 patients (889 receiving chronic opioids) being treated by 235 primary care physicians. Standardized questionnaires and medical record reviews were used to assess rates of addiction, pain diagnosis and severity, opioid adverse effects, and mental health. The mean daily dose of opioids was 92 mg using a morphine-equivalent conversion. Side effects included constipation (40 percent), sleeping problems (25 percent), loss of appetite (23 percent), and sexual dysfunction (18 percent), with patients on daily opioids experiencing more side effects than subjects on intermittent medication. The Medical Outcomes Study Mental Health Inventory (MOS-MHI) cognitive functioning scale indicated poorer cognitive function in the overall sample of chronic pain patients as compared to a general clinical sample (delta x 95 percent CI = 9.28, 13.76). However, there were limited differences in MOS scores between chronic pain subjects on daily opioids vs. intermittent opioids vs. no prescription opioids. A regression model suggests that psychological measures and pain severity are more predictive of decrements in cognitive function than specific opioid preparations or daily opioid dose. Physicians should closely monitor patients for adverse effects and adequacy of pain control when using chronic opioid therapy for chronic pain treatment. Psychological health, an important predictor of cognitive dysfunction, is a particularly important measure to actively monitor and manage.