"The lifetime medical use of prescription opioids was reported by approximately 14.0% of those who did not engage in past-year nonmedical use of prescription opioids, 76.1% of nonmedical users of prescription opioids motivated only by pain relief, 71.4% of those motivated by pain relief and other motives, and 46.7% of those who reported non-pain relief motives only (p < 0.001). Among past-year nonmedical users of prescription opioids, approximately 56.5% of those motivated only by pain relief as compared to 23.1% of those who reported pain relief and other motives, and 14.2% of those who reported only non-pain relief motives had initiated medical use of prescription opioids before nonmedical use of prescription opioids. In contrast, approximately 19.6% of those motivated only by pain relief as compared to 48.3% of those who reported pain relief and other motives, and 32.5% of those who reported only non-pain relief motives initiated nonmedical use of prescription opioids before medical use of prescription opioids."