Intensely conflicted about his desire and ruinously self-aware of its torment, Samuel Coleridge described his poem Kubla Khan as ‘a fragment composed in a sort of reverie brought on by two grains of opium, taken to check a dysentery.’ It probably deranged his will and paralysed his power of expression during his sunset years. Writing in Coleridge and Opium Eating, Thomas De Quincey – him of Confessions of an English Opium-Eater fame – observed that ‘There are, in fact, two classes of temperament as to this terrific drug . . . those which genially expand to its temptations, and those which frostily exclude them.’ The books and lives of these literary geniuses held more of warning than of attraction to opium. Closer to home, but not very close to comfort, is the opium epidemic plaguing Punjab, where whole swathes of villages, and its youngsters, are addicted to opium. So much so that it made it to the election manifesto of many a political party in the recently held elections, and has now replaced cannabis as the choice of drug abusers. Some now are in rehabilitation, many are not. From a medical perspective, it is imperative to understand the research underpinning the management of acute pain in opium addicts, whether in rehabilitation or otherwise.
Wachholtz and Gonzalez, in their recent paper, evaluated the changes in pain sensitivity and tolerance with opioid maintenance treatments; and duration of this effect after treatment cessation. 120 Individuals with chronic pain were recruited in 4 groups (N = 30): 1-methadone for opioid addiction; 2-buprenorphine for opioid addiction; 3-history of opioid maintenance treatment for opioid addiction but with prolonged abstinence and 4-opioid naïve controls. Participants completed a cold water task including, time to first pain (sensitivity) and time to stopping the pain task (tolerance). While the rating of pain induced by the cold pressor task was not significantly different between the groups, the groups receiving current and past treatment with opioid maintenance medication had increased sensitivity and decreased tolerance to pain relative to the opioid naïve control group. Tolerance to pain was better among those with a history of opioid maintenance compared to active methadone patients, with the highest tolerance found among opioid naïve control group participants. Correlations within the prolonged abstinent group indicated pain tolerance was significantly improved as length of opioid abstinence increased; but duration of abstinence did not alter sensitivity.
Animal studies exploring potential physiological mechanisms for the hyperalgesia have ranged from genetics, to specific NMDA or glutamate pathways, to descending pathways from the brain stem and the ascending pathways in the dorsal horn of the spinal column. There is a limited understanding of the effect of hyperalgesia in the treatment of acute pain among patients with a history of addiction to opioids, and limited awareness of the psychological and physiological aspects that inform the pain experience in individuals with a history of opioid addiction and/or on maintenance. There is then the concern (and the debate) that addictive behaviours might be resumed when opioids are administered for pain in individuals with a history of addiction. But, will such increased sensitivity induce a chronic pain patient to abuse a prescribed opioid analgesic, or in other words alter the pain experience of an individual with co-morbid chronic pain? The critical intersection between opioid addiction/maintenance and chronic (nonmalignant) pain has been poorly studied. We understand, however, that – opioid prescribing to treat chronic pain is on the rise; there is a simultaneous rise (50%) in reported cases of abuse of opioid analgesics; the lifetime prevalence for opioid abuse disorders among chronic pain patients is approximately 35%; among those entering methadone treatment, 37% reported chronic pain, of which 65% reported severe pain; and comorbid pain and addiction patients also report abusing illegal drugs, alcohol, or prescription medications to treat their pain.
It is handy to remember that Coleridge and De Quincey made their first acquaintance with opium in the treatment of a physical disorder – Coleridge for the relief of rheumatic pain, and De Quincey for his trigeminal neuralgia. There is no evidence that it increased their artistic achievements or improved their magnificent intellect, but likely increased their sensitivity and reduced their tolerance to pain. The current study found no differences in the level of pain experienced or the desire to use opioids after a pain event between groups. The psychology questionnaire which they used, however, suggests that the ‘sense of control’ over opioids appears to be what differentiates active opioid users from those who have achieved prolonged abstinence. Any treatments addressing co-morbid pain and opioid addiction, therefore, need to use cognitive behavioral tools to improve pain tolerance and pain self-efficacy. Such an integrated psychosocial approach of increasing tolerance to pain, self-efficacy, and control over opioid use might improve the efficacy of treatment for this difficult to treat disorder.